AU2016203453B2

AU2016203453B2 - Hydrometallurgy and separation method of rare earth ores

Info

Publication number: AU2016203453B2
Application number: AU2016203453A
Authority: AU
Inventors: Dali Cui; Zongyu FENG; Xiaowei Huang; Xinlin Peng; Xu SUN; Liangshi Wang; Meng Wang; Yuqing WEI; Yang Xu; Shuai Yi
Original assignee: Grirem Advanced Materials Co Ltd
Current assignee: Grirem Advanced Materials Co Ltd
Priority date: 2015-05-26
Filing date: 2016-05-26
Publication date: 2021-08-05
Anticipated expiration: 2036-05-26
Also published as: AU2016203453A1; MY190216A; CN106282553B; CN106282553A

Abstract

The present invention provides a hydrometallurgy and separation method of rare earth ores. Leaching and neutralizing a sulfate roasted ore by a magnesium bicarbonate aqueous solution to remove impurities, and performing solid-liquid separation to obtain a magnesium-containing rare earth sulfate solution; performing extraction-transformation using P507 or P204 saponified by a magnesium bicarbonate aqueous solution or magnesium bicarbonate precipitation transformation and enrichment to obtain a mixed rare earth chloride solution having a high concentration, and then performing extraction separation and precipitation using a magnesium bicarbonate aqueous solution to recycle rare earths so as to obtain a plurality of rare earth compound products. Magnesium sulfate wastewater produced in the technical process above is subjected to alkali conversion by using a cheap alkali compound including calcium, magnesium and so on, and C02 recycled in the hydrometallurgy and separation process is introduced to perform purification by carbonating so as to obtain a magnesium bicarbonate aqueous solution that is recycled and used in processes including leaching, transformation, extraction separation and precipitation of rare earths, thereby implementing cyclic utilization of magnesium and C02, zero emission of ammonia nitrogen and wastewater, and greatly reducing production cost, improving the rare earth recovery rate and implementing green and environment-friendly, efficient and clean production of rare earths. 50 Rare earth Ore Sulfatizinkgroasingj Leachirg reutraizaion Magnesium Leslr ~ and mpu ty bicarbonate-containing Cacum ureoaluinrg a - alkaline solution res e rnesum sulfate Bicarbonate aqueous SOlutior Magnei nc rare earth slate o ufion 1S Xrrconainintagne u r --t h wdrxde and calcium sulfate E tractin .........t ................ trarsformation/ I Extraction precip itation transformation separation ~pH value adusted Calcium_;r-_ Extract onrn separton k nire substance Rare ea:rh so u on Srnetng recipitation by using a wastewater magnesium bicarbonate aqueous solution Fig. 1 51

Description

Rare earth Ore

Sulfatizinkgroasingj

Leachirg reutraizaion Magnesium Leslr ~ and mpu ty bicarbonate-containing Cacum ureoaluinrg a - alkaline solution res e rnesum sulfate Bicarbonate aqueous SOlutior

Magnei nc rare earth slate o ufion

1S Xrrconainintagne u r --t E tractin h wdrxde and calcium .........t sulfate ................ trarsformation/ I Extraction precip itation transformation separation ~pH value adusted

Calcium_;r-_ Extract onrn separton k nire substance

Rare ea:rh so u on

Srnetng recipitation by using a wastewater magnesium bicarbonate aqueous solution

Fig. 1

Hydrometallurgy and separation method of rare earth ores

Technical field of the invention The present invention relates to the field of metallurgy and separation of rare earth ores, particularly to a hydrometallurgy and separation method of rare earth ores.

Background of the invention At present, a solvent extraction method is generally applied in hydrometallurgy, separation and purification of rare earths. However, there existed some problems in rare earth hydrometallurgy process including high consumption of acids and alkalis, high cost, a large amount of discharged wastewater and so on. For example, a major process of sulfatizing roasting---water-leaching---magnesium oxide neutralization and impurity removal---extraction transformation or extraction separation is applied to a mixed rare earth ores in Baotou, and it is necessary to add a lot of solid magnesium oxides into an obtained rare earth sulfate solution so as to neutralize the residual acid, regulate the pH value and remove impurities. A large amount of waste residue is formed by unreacted magnesium oxides and impurities thereof due to a high impurity content of light-burned magnesium oxide and a slow reaction rate. A lag of the change of the pH value can be hardly controlled, which leads to a loss of rare earth precipitation. In addition, a lot of rare earth ions are adsorbed by waste residues, resulting in the reduction of the recovery rate of rare earths. A large amount of acid wastewater containing sulfuric acid and magnesium sulfate is generated during the extraction transformation and separation processes of rare earths, which requires neutralization using a lot of alkali. A lot of calcium ions contained in the wastewater are recycled and enriched easily to form a calcium sulfate crystal that blocks a pipeline, or a three-phase substance is formed during the extraction process to affect phase separation and so on, and the wastewater can be hardly recycled. An organic extractant is saponified by using aqueous ammonia or sodium hydroxide in a conventional rare earth hydrometallurgy process to replace and remove hydrogen ions, and then the organic extractant is exchanged with rare earth ions to extract and separate the rare earth ions. However, a large amount of liquid ammonia or liquid alkali is consumed in the extraction process, thus increasing the cost and generating a large amount of ammonia-nitrogen wastewater or wastewater with a high sodium salt content and so on. In a conventional chemical neutralization method, lime or a carbide residue and so on is added to neutralize a large amount of acid wastewater, and a lot of precipitates including calcium sulfate, calcium fluoride, or magnesium hydroxide and so on are produced. The clarified wastewater is discharged under standards. A neutralizer including lime or carbide residue and so on is mainly consumed in the process, but the processed wastewater has saturated contents of calcium ions, magnesium ions, and sulfate ions. When the wastewater is recycled, scaling including calcium sulfate and so on is easily formed on a pipeline, a transmission pump, or a storage tank as temperature changes, thus seriously affecting cyclic utilization of the wastewater and largely influencing continuous production. Besides, the wastewater discharged directly contains a lot of salts, which will increase the amount of total dissolved solid in the river and bring with more and more serious pollution to soil, surface water and groundwater to endanger the ecological environment. With the promulgation and application of a new environment protection law, the ultimate goal will be a solution to the problem of high salt wastewater and implementation of near zero emission of wastewater. At present, in rare earth hydrometallurgy wastewater recycling researchment and application, a lot of researches have put emphasis on application of a membrane separation method, an evaporation crystallization method, a steam stripping method, a break point chlorination method and so on.

The membrane separation method, which separates ions, molecules, or particles in water by using permselectivity, has a good processing effect, but it is easy to cause membrane pollution. The evaporation crystallization method is a separation method of evaporating and concentrating salt-containing wastewater to a supersaturated state, so that a crystal nucleus is formed by a salt in the wastewater, and then gradually generating a crystal solid. The method is applicable to processing of high salinity wastewater. The steam stripping method, which enables direct contact of wastewater and water vapour so as to enable a volatile substance in the wastewater to diffuse into a gas phase according to a certain proportion so as to separate a pollutant from the wastewater, is used for processing a volatile pollutant. The break point chlorination method adds a certain amount of a chlorine or sodium hypochlorite into wastewater so as to oxidize ammonia nitrogen in the wastewater into N2,

thus removing ammonia nitrogen. These methods have disadvantages including high operation cost and high investment cost, thereby limiting industrial application. However, it is still necessary to improve the existing rare earth hydrometallurgy and separation methods so as to simplify the production process, improve the rare earth recovery rate, reduce the amount of residue discharge and reduce production cost.

Summary of the invention The present invention mainly aims to provide a hydrometallurgy and separation method of rare earth ores so as to simplify a hydrometallurgy and separation production process of the rare earth ores, improve a rare earth recovery rate, reduce an amount of residue discharge and reduce production cost. A hydrometallurgy and separation method of rare earth ores is provided according to an aspect of the present invention so as to implement the purpose above. The method comprises: Step 1: leaching and neutralizing a rare earth roasted ore obtained by sulfatizing roasting by a magnesium bicarbonate aqueous solution to remove impurities, and performing solid-liquid separation and obtaining a magnesium-containing rare earth sulfate solution and a leaching residue; and Step 2: preparing a rare earth compound product by using the magnesium-containing rare earth sulfate solution as a raw material. Further, in Step 1, the rare earth ores is a mineral containing at least one of monazite, xenotime, and bastnaesite. Further, a concentration of the magnesium bicarbonate aqueous solution is 2 g/L to 25 g/L (based on MgO), preferably 4 g/L to 18 g/L, and the pH value of the obtained magnesium-containing rare earth sulfate solution is 3.5 to 4.5 in Step 1. Preferably, a rare earth content in the magnesium-containing rare earth sulfate solution is 10 g/L to 45 g/L, preferably 25 g/L to 40 g/L based on Rare Earth Oxides (REO) in Step 1. Preferably, Step 2 comprises: Step 21: performing extraction transformation or precipitation transformation on the magnesium-containing rare earth sulfate solution, and obtaining a mixed rare earth solution and a first wastewater that contains magnesium sulfate; Step 22: extracting and separating the mixed rare earth solution, and obtaining a rare earth solution and a second wastewater; and Step 23: reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a third wastewater; or Step 2 comprises: Step 21': extracting and separating the magnesium-containing rare earth sulfate solution, and obtaining a rare earth solution and a fourth wastewater that contains magnesium sulfate; and Step 22': reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a fifth wastewater, wherein an extractant used in the step of extraction transformation or extraction separation is an organic extractant saponified by a magnesium bicarbonate aqueous solution, and a precipitant used in the step of extraction transformation is a magnesium bicarbonate aqueous solution and the rare earth content in the rare earth solution is 200 g/L to 300g/L based on REO. Further, the method further comprises a recovery processing step of hydrometallurgy wastewater generated in the hydrometallurgy and separation process, wherein the hydrometallurgy wastewater comprises at least one of the first wastewater and the fourth wastewater, and at least one of the second wastewater, the third wastewater and the fifth wastewater; preferably, the recovery processing step comprises: Step A: regulating the pH value of the hydrometallurgy wastewater to 10.0 to 12.5 by using a calcium-containing alkaline substance, and obtaining a slurry containing magnesium hydroxide and calcium sulfate; and Step B: carbonizing the slurry containing magnesium hydroxide and calcium sulphate, and obtaining a magnesium bicarbonate-containing alkaline solution and a solid residue. Further, when the pH value of the hydrometallurgy wastewater is less than 2.0, Step A comprises: Step Al: regulating the pH value of the hydrometallurgy wastewater to 4.0 to 10.0 by using the calcium-containing alkaline substance, and obtaining a solid-liquid mixture; Step A2: performing solid-liquid separation on the solid-liquid mixture, and obtaining a filtrate; and Step A3: regulating the pH value of the filtrate to 10.0 to 12.5 by using the calcium-containing alkaline substance, and obtaining the slurry containing magnesium hydroxide and calcium sulfate. Further, Step A further comprises a step of adding a calcium sulfate crystal seed into the hydrometallurgy wastewater, and/or performing an aging treatment on the slurry containing magnesium hydroxide and calcium sulfate, preferably a duration of the aging treatment is 0.5 h to 6h. Further, Step B comprises: introducing a C02 gas into the slurry containing magnesium hydroxide and calcium sulfate so as to perform a carbonization treatment, and controlling the pH value of the slurry within 7.0 to 8.0 during the carbonization treatment, and obtaining a carbonized slurry; and performing solid-liquid separation on the carbonized slurry, and obtaining the magnesium bicarbonate-containing alkaline solution and the solid residue. Further, the solid residue is acidized to obtain calcium sulfate, or returned into the hydrometallurgy and separation process of the rare earth ores to neutralize and process an acid wastewater in the hydrometallurgy wastewater so as to obtain calcium sulfate. Further, the concentration of calcium ions in the magnesium bicarbonate-containing alkaline solution is 0.01 g/L to 0.7 g/L, preferably 0.01 g/L to 0.4 g/L. Further, the magnesium bicarbonate-containing alkaline solution is returned to the hydrometallurgy and separation method of the rare earth ores to be recycled as the magnesium bicarbonate aqueous solution. Further, the organic extractant is at least one of P507, P204, P229, C272, C301, C302 and C923, preferably P507 and/or P204. By applying the technical solution of the present invention, a rare earth roasted ore obtained by sulfatizing roasting is leached by a magnesium bicarbonate aqueous solution, which can not only leach rare earths to obtain a rare earth sulfate solution (10 to 45 g/L), but also implement functions including consumption of a residual acid, neutralization and regulation of the pH value, so that impurity ions including iron ions, phosphorus ions, thorium ions and so on in the rare earth ores are precipitated into a waste residue to be removed. Compared with a traditional method for removing impurities by neutralization with solid magnesium oxide, the present invention applies an alkalescent solution, i.e. the magnesium bicarbonate aqueous solution, thus the content of impurities is low, and an amount of residues and loss of entrained rare earths may be reduced. In addition, the reaction speed is fast, and it is easy to control the pH value accurately so as to reduce loss of the rare earths in the impurity removal and improve the recovery rate of the rare earths, thus implementing multiple effects including ore leaching, neutralization and impurity removal, and simplification of a technical process.

Besides, by applying a preferred implementation solution of the present invention, the obtained rare earth sulfate solution having a low concentration (10 to 45 g/L) is subjected to extraction transformation and enrichment by using P507 or P204 saponified by a magnesium bicarbonate aqueous solution or precipitation transformation and enrichment by using a magnesium bicarbonate aqueous solution, thereby obtaining a mixed rare earth chloride solution (200 to 300 g/L) with a high concentration, the mixed rare earth chloride solution is then extracted and separated, and precipitated with a magnesium bicarbonate aqueous solution to recover rare earths and obtain a plurality of rare earth compound products. Magnesium sulfate containing wastewater generated in the technical process is subjected to alkali conversion by using a cheap alkali compound including calcium, magnesium and so on, and C02 recycled in the hydrometallurgy and separation process is introduced to perform purification by carbonating so as to obtain a magnesium bicarbonate aqueous solution that is recycled and used in processes including leaching, extraction separation and precipitation of rare earths, thereby implementing cyclic utilization of magnesium and C02, zero emission of ammonia nitrogen and wastewater, and greatly reducing production cost, improving the rare earth recovery rate and implementing green and environment-friendly, efficient and clean production of rare earths.

Brief description of the drawings The accompanying drawings in the specification, which form a part of the present application, are used for providing further understanding to the present invention. The schematic embodiments of the present invention and description thereof are used for explaining the present invention, instead of forming improper limitation thereto. In the accompanying drawings: Figure 1 is a flowchart of a hydrometallurgy and separation method of rare earth ores in a typical embodiment according to the present invention.

Detailed description of the embodiments It needs to be noted that the embodiments in the present application and the characteristics in the embodiments may be combined with each other if there is no conflict. The present invention will be expounded below in combination with the embodiments. In the present invention, extraction transformation means that all rare earth ions in a rare earth sulfate solution with low concentration (REO 10 to 45g/L) are extracted into an organic phase by using the organic phase (organic extractant), then reverse extraction is performed by using hydrochloric acid or nitric acid to obtain a rare earth chloride solution or a rare earth nitrate solution (REO 200 to 300g/L) with high concentration. Precipitation transformation means that rare earth ions in a rare earth sulfate solution are precipitated by using a magnesium bicarbonate aqueous solution to prepare a rare earth carbonate which is then dissolved with hydrochloric acid or nitric acid to obtain a rare earth chloride solution or a rare earth nitrate solution having a high concentration. As mentioned in the background, a hydrometallurgy and separation method of rare earth ores in the priority art has various problems including an expensive wastewater processing process, damage caused by direct discharge of wastewater generated by a separation process on an ecological environment, or an impact on continuous production of an enterprise caused by easy scaling during a recycling process and so on. A hydrometallurgy and separation method of rare earth ores is provided in a typical embodiment of the present invention in order to improve the conditions above, as shown in Fig. 1. The method includes: Step 1: leaching and neutralizing a rare earth roasted ore obtained by sulfatized-roasting by a magnesium bicarbonate aqueous solution to remove impurities, and performing solid-liquid separation, and obtaining a magnesium-containing rare earth sulfate solution and a leaching residue; and Step 2: preparing a rare earth compound product by using the magnesium-containing rare earth sulfate solution as a raw material.

A rare earth roasted ore obtained by sulfatizing roasting is leached by water in the priority art to obtain a rare earth sulfate-containing acid solution and a water leached residue, then solid magnesium oxide is added to consume a residual acid and regulate the pH value through neutralization, and solid-liquid separation is performed to obtain a rare-earth-sulfate-containing solution and a neutralized residue, while a large amount of solid residue formed by magnesium oxide not reacted completely and impurities therein, and impurities including iron, phosphorus, thorium and so on are precipitated into the neutralized residues. However, the rare earth roasted ore obtained by the sulfatizing roasting is leached by the magnesium bicarbonate aqueous solution according to the separation method in the present embodiment, which can not only extract rare earths to obtain the rare earth sulfate solution, but also implement functions including consumption of a residual acid, neutralization and regulation of the pH value, so that impurity ions including iron ions, phosphorus ions, thorium ions and so on in the rare earth ores are precipitated into a leaching residue so as to remove impurities. The method of the present invention improves the leaching rate of the rare earths, thereby implementing multiple effects including ore leaching, neutralization and impurity removal, and simplification of a technical process, and reducing the amount of the residue. The alkalescent magnesium bicarbonate aqueous solutions applied in the present invention are to consume the residual acid and neutralize and regulate the pH value. When solid alkalis including calcium oxide, magnesium oxide and so on are applied, an acid is neutralized by calcium oxide to form a large amount of calcium sulfate residue, thus resulting in serious rare earth absorption loss, while magnesium oxide which reacts slowly, will result in a change lag of a system pH value and thus the pH value can be hardly controlled in practical operation, and the pH value of a final filtrate obtained after liquid and solid separation seriously deviates from an expected set value, thus resulting in relatively large loss of rare earth elements in the system. However, leaching cannot be implemented effectively if a monovalent cation-containing alkaline substance such as sodium carbonate, sodium hydroxide, aqueous ammonia is applied because monovalent cations are easy to react with the rare earth elements in a sulfuric acid system to form a rare earth double sulfate precipitation which makes the rare earth elements enter the leaching residue. A rare earth double sulfate precipitation will not be produced if the roasting product obtained by sulfatizing roasting is leached by a magnesium compound. In the meanwhile, since an extractant has a stronger extraction capability than that of magnesium ions on rare earth ions, thus the magnesium ions can be hardly extracted together with the rare earth ions in a subsequent process, thus avoiding influence caused by the extractant on separation and purification of the rare earth elements during an extraction method applied subsequently. The rare earth ores that can be separated by the separation method is applicable to all rare earth ores that require acidification roasting and leaching. Preferably, the rare earth ores in the present invention is at least one of monazite, xenotime, and bastnaesite. When the roasted ore is leached by using the magnesium bicarbonate aqueous solution, the rare earth roasted ore may be prepared into a slurry by using a small amount of water firstly so as to prevent an excessively high local alkalinity, and the slurry is then leached and neutralized by using a magnesium bicarbonate aqueous solution to remove impurities. In a preferred embodiment of the present invention, the concentration of the magnesium bicarbonate aqueous solution is 2 g/L to 25 g/L (based on MgO), preferably 4 g/L to 18 g/L, and the pH value of the obtained magnesium-containing rare earth sulfate solution is 3.5 to 4.5 in Step 1. The magnesium bicarbonate aqueous solution with a concentration of 2 g/L to 25 g/L is applied, which can not only effectively neutralize a residual acid and regulate the pH value, but also obtain a rare earth solution having a moderate concentration. When the pH value of the magnesium-containing rare earth sulfate solution is below 3.5, rare earths can be hardly precipitated to cause loss, thus the recovery rate of the rare earths is slightly higher. However, impurity elements including iron, phosphorus, thorium and so on cannot be completely precipitated, which affects the purity of the rare earth sulfate solution, subsequent extraction separation and product quality. If the pH value is controlled to be higher than 4.5, the impurities are precipitated and removed completely, but rare earth ions are easily formed hydroxide precipitations, thus causing loss. Therefore, when the pH value is controlled at 3.5 to 4.5, the impurity ions including iron, phosphorus, thorium and so on in the rare earth ores are precipitated into the leaching residue, while the rare earth elements are still in an aqueous phase with little loss. The roasted ore is leached by the magnesium bicarbonate aqueous solution in the ore leaching step in the separation method. In order to improve the leaching rate of rare earths, the concentration and addition amount of the magnesium bicarbonate aqueous solution are controlled so that the content of rare earths in the obtained magnesium-containing rare earth sulfate solution reaches 10 g/L to 45 g/L based on REO, preferably 25 g/L to 40 g/L. The content of the rare earths in the magnesium-containing rare earth sulfate solution is improved, which can improve the production efficiency. However, a rare earth sulfate crystal is generated easily to affect the leaching rate when the content of the rare earths is higher than 45 g/L. It is indicated by the rare earth content in such a range that the separation method of the present invention not only has a simplified process, but also has a high rare earth leaching rate, and can be massively popularized. In the hydrometallurgy and separation step of the rare earth ores according to the present invention, the rare earth compound product may be prepared by using the magnesium-containing rare earth sulfate solution as the raw material according to a method of the priority art. In a preferred embodiment of the present invention, Step 2 includes: Step 21: performing extraction transformation or precipitation transformation on the magnesium-containing rare earth sulfate solution, and obtaining a mixed rare earth solution and a first wastewater that contains magnesium sulfate; Step 22: extracting and separating the mixed rare earth solution, and obtaining a rare earth solution and a second wastewater; and Step 23: reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a third wastewater; or Step 2 comprises: Step 21': extracting and separating the magnesium-containing rare earth sulfate solution, and obtaining a rare earth solution and a fourth wastewater that contains magnesium sulfate; and Step 22': reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a fifth wastewater, wherein an extractant used in the step of extraction transformation or extraction separation is an organic extractant saponified by a magnesium bicarbonate aqueous solution, and a precipitant used in the step of extraction transformation is a magnesium bicarbonate aqueous solution and the rare earth content in the rare earth solution is 200 g/L to 300g/L based on REO. In the preferred embodiment, the magnesium-containing sulfate rare earth solution is prepared into a rare earth solution, a rare earth precipitation or rare earth oxides, which can provide various rare earth raw materials for preparing different rare earth products. Moreover, the extractant is saponified by the magnesium bicarbonate aqueous solution so that the extraction process can be controlled precisely, the pH value can be balanced, the rare earths can be extracted more completely, the recovery rate of the rare earths is higher, the flow rate is easily controlled precisely, a three-phase substance will not be generated, and ammonia-nitrogen wastewater will not be produced. The magnesium bicarbonate aqueous solution is applied to performing the precipitation transformation on the rare earth solution, so that the pH value of the precipitation process can be controlled precisely, the precipitation yield of the rare earths is high and the crystallization performance is excellent. In the preferred embodiment of the present invention, the organic extractant is saponified by the magnesium bicarbonate aqueous solution. A reasonable mass concentration of the magnesium bicarbonate aqueous solution is selected according to different types of organic extractants and different contents of rare earth elements in a solution to be extracted. In a preferred embodiment of the present invention, the concentration of the magnesium bicarbonate aqueous solution for saponifying the organic extractant is 2 g/L to 25 g/L (based on MgO), preferably 4 g/L to 18 g/L. The magnesium bicarbonate aqueous solution with a mass concentration in the range above is applied to saponifying the organic extractant so that the organic extractant can extract the rare earth elements more effectively. By means of extraction separation, the content of the rare earths in the rare earth solution reaches 200 g/L to 300 g/L based on REO, thus the rare earth elements in the solution are effectively separated, purified or enriched. A step of recycling the hydrometallurgy wastewater generated in the hydrometallurgy and separation process is also included in the hydrometallurgy and separation method in another preferred embodiment of the present invention so as to save energy, protect the environment and improve the cyclic utilization rate of materials, wherein the hydrometallurgy wastewater includes the first wastewater, the second wastewater, the third wastewater, the fourth wastewater and the fifth wastewater. Preferably, the recovery processing step includes: Step A: regulating the pH value of the hydrometallurgy wastewater to 10.0 to 12.5 by using a calcium-containing alkaline substance, and obtaining a slurry containing magnesium hydroxide and calcium sulfate; and Step B: carbonizing the slurry containing magnesium hydroxide and calcium sulfate, and obtaining a magnesium bicarbonate-containing alkaline solution and a solid residue (as shown in Fig. 1). The calcium-containing alkaline substance also includes a calcium and magnesium-containing alkaline substance. The hydrometallurgy wastewater is reacted by using the calcium-containing alkaline substance or the calcium and magnesium-containing alkaline substance, and the pH value is controlled in a range of 10.0 to 12.5 so that a lot of magnesium ions in the hydrometallurgy wastewater are precipitated in a form of magnesium hydroxide while calcium ions are precipitated in a form of calcium sulfate, so as to obtain the slurry containing magnesium hydroxide and calcium sulfate. Step A further includes a step of adding a calcium sulfate crystal seed into the rare earth hydrometallurgy wastewater, and/or performing aging processing in another preferred embodiment of the present invention so that the calcium ions in the hydrometallurgy wastewater may be precipitated as much as possible and as quickly as possible. Subsequently, a carbonization treatment is performed by using C02 so as to convert solid magnesium hydroxide into a magnesium bicarbonate aqueous solution while the calcium sulfate still exists in a form of a precipitation. Even if a small amount of calcium sulfate is dissolved slightly to release calcium ions, these calcium ions will be also precipitated in the carbonization treatment as calcium carbonate which is subjected to solid-liquid separation, thereby effectively separating calcium ions and magnesium ions in the recycled magnesium bicarbonate-containing alkaline solution. The hydrometallurgy wastewater is neutralized by the calcium-containing alkaline substance or the calcium and magnesium-containing alkaline substance. Since the wastewater is an acid wastewater containing magnesium sulfate, the alkaline substance above is able to neutralize a residual acid in the acid wastewater, and the calcium ions will be combined with sulfate ions to form calcium sulfate precipitation, and thus are removed, thereby not only neutralizing the residual acid, but also reducing the calcium ions in the wastewater, and further solving the problem of scaling during reuse of the recycled water. In the meanwhile, the obtained slurry is carbonized, which is able to not only convert magnesium hydroxide into soluble magnesium bicarbonate which is dissolved in water, but also further remove a small amount of remaining calcium ions in the slurry by converting the same into calcium carbonate, thus obtaining the magnesium bicarbonate-containing solution and the solid residue. A magnesium bicarbonate solution with a low content of calcium ions may be obtained by applying the hydrometallurgy wastewater recycling step above. In order to more effectively reduce the content of calcium ions in the magnesium bicarbonate solution and improve the processing effect and the water recycling efficiency, in another preferred embodiment of the present invention, when the pH value of the hydrometallurgy wastewater is less than 2.0, the step above includes: Step Al: regulating the pH value of the hydrometallurgy wastewater to 4.0 to 10.0 by using the calcium-containing alkaline substance, and obtaining a solid and liquid mixture; Step A2: performing solid-liquid separation on the solid and liquid mixture, and obtaining a filtrate; and Step A3: regulating the pH value of the filtrate to 10.0 to 12.5 by using the calcium-containing alkaline substance, and obtaining the slurry containing magnesium hydroxide and calcium sulphate. The calcium ions in the hydrometallurgy wastewater may be removed more effectively by precipitating the calcium ions so as to separate the same from magnesium ions step by step in Step A. Firstly, the calcium-containing alkaline substance is added and the pH value of the hydrometallurgy wastewater is regulated to 4.0 to 10.0. In this range of pH values, a calcium sulfate precipitation is formed by the calcium ions and sulfate ions while the magnesium ions still exist in a form of ions. After the calcium sulfate is filtered and removed, the calcium-containing alkaline substance or the calcium and magnesium-containing alkaline substance is further added into a filtrate so that the pH value of the filtrate is in a range of 10.0 to 12.5, thereby converting the magnesium ions into magnesium hydroxide and forming the slurry of magnesium hydroxide and calcium sulfate. Neutralization and precipitation are performed step by step. In the first step, the calcium sulfate produced by the acid in the hydrometallurgy wastewater is neutralized, filtered and removed, thereby reducing the content of calcium sulfate in a magnesium hydroxide slurry, and the carbonation rate of magnesium can be improved while reducing the content of calcium ions in the magnesium bicarbonate solution. Besides, the calcium and magnesium-containing alkaline substance is added in the second step, which may also improve the carbonation rate of magnesium, and reduce the content of calcium ions in the magnesium bicarbonate solution. Specific equations are as follows: 2H+(liquid) +S04 2 -(liquid) +Ca(OH)2(solid)-CaSO4(solid) +H20(liquid) Mg2+(liquid) +S04 2 -(liquid) + Ca(OH)2(solid)- Mg(OH)2(solid) +CaSO4(solid) As many as calcium ions in the hydrometallurgy wastewater may be precipitated and removed in the step of forming the calcium sulfate precipitation. In order to improve the precipitation rate or precipitate the calcium ions more completely, in another preferred embodiment of the present invention, Step Al and Step A3 further include a step of adding a calcium sulfate crystal seed into the rare earth hydrometallurgy wastewater, and/or a step of performing aging processing on the solid and liquid mixture or the slurry containing magnesium hydroxide and calcium sulfate. The calcium sulfate crystal seed is added to so that the calcium sulfate is easier to precipitated, and the precipitation is relatively thorough while the aging processing also makes the precipitation complete. A specific aging duration may be adjusted appropriately according to an amount of processed hydrometallurgy wastewater. In a preferred embodiment of the present invention, the aging duration is longer than 0.5h, and less than or equal to 6h. When the aging duration is longer than 0.5h, the aging becomes effective, and the content of calcium ions is reduced. The aging duration is controlled within 6h, which enables the calcium sulfate to precipitate more thoroughly, thus facilitating reuse of the processed water. Operations of the whole technical process will be delayed if the duration is longer, which hinders the whole technical process. The hydrometallurgy wastewater recycled and processed in the present invention is wastewater containing magnesium ions. The wastewater mainly contains Mg 2 +, H+ and S042 -, and may also contain one or more of Na+, CI- and N03-. The system is complicated, and there is a variety of impurity ions. When the wastewater is processed by the calcium-containing alkaline substance, the calcium ions will exist in a form of the calcium sulfate precipitation in the system of sulfate ions, and form a solid mixture with magnesium hydroxide to be used together in the carbonizing step. During the carbonizing process, bicarbonate radicals will be induced to generate a calcium carbonate crystal if a lot of calcium ions exist in the system, thereby reducing the carbonizing rate of magnesium, decomposing magnesium bicarbonate and precipitating a magnesium carbonate solid, and affecting continuous production after massive scaling. Therefore, the present invention reasonably controls the pH value during the alkali conversion process to generate a stable crystal calcium sulfate precipitation with low activity, so that the concentration of calcium ions in an aqueous phase after the alkali conversion is reduced, and the calcium sulfate with low activity is not easy to further dissolve into calcium ions that reduce the carbonizing rate. The pH value is controlled by stage in the preferred embodiment above, thus implementing segmented alkali conversion of the calcium ions and the magnesium ions. Subsequently, solid-liquid separation is performed to remove some calcium first, thus reducing the concentration of calcium ions in an aqueous phase during an initial phase of the carbonizing. The crystal seed is further added, and/or the aging processing is performed so that calcium ions are precipitated more thoroughly during the segmented alkali conversion and precipitation, thus the concentration of calcium ions in the aqueous phase during the initial phase of the carbonizing is lower, and better carbonizing effect is implemented. In another preferred embodiment of the present invention, Step B of carbonizing (as shown in Fig. 1) the slurry to obtain the magnesium dicarbonate-containing solution and the solid residue among the steps above includes: introducing a C02 gas into the slurry to perform a carbonization treatment, and controlling the pH value of the slurry within 7.0 to 8.0 during the carbonization treatment, and obtaining a carbonized slurry; and performing solid-liquid separation on the carbonized slurry, and obtaining the magnesium bicarbonate-containing alkaline solution containing magnesium dicarbonate and the solid residue. The wastewater after the neutralization and precipitation processing is a mixed slurry containing Mg(OH)2 and CaS04. Since CaSO4 is slightly soluble, the slurry further contains a small amount of Ca 2 +, OH- and S042-. The carbonization is performed by using the C02 gas so as to convert the solid Mg(OH)2 into a Mg(HC03)2 solution, and convert free Ca 2 + into a CaC03 precipitation, curing transformation of calcium is promoted again, thus further removing calcium from the aqueous phase. Specific equations of the carbonization process are as follows: Mg(OH)2(solid) + 2CO2(gas) -Mg(HCO3)2(liquid) Ca2+(liquid)+2HCO3-(liquid)-CaCO3(liquid)+ H20(liquid)+ C02(gas) The following side reaction may occur during the carbonization reaction: Mg(OH)2(solid)+ C02(solid)+ H20-MgCO3• 3H20(solid) In the preferred embodiment above, the pH value of the slurry is controlled within a range of 7.0 to 8.0 to control the amount of introduced C02, so that the calcium ions in the slurry may be removed by precipitating in a form of calcium carbonate as much as possible, thus separating calcium and magnesium, and reducing the concentration of calcium ions in the obtained magnesium bicarbonate aqueous solution as much as possible. The time of the carbonization treatment in the carbonizing step may be adjusted appropriately according to the content of the magnesium element and the content of the calcium element in the slurry. In a preferred embodiment of the present invention, the time of the carbonization treatment is 10min to 120min, more preferably 20min to 60min. The magnesium hydroxide precipitation may be effectively converted into a magnesium bicarbonate aqueous solution while the processing efficiency is relatively high within 10min to 120min, while the magnesium hydroxide precipitation may be converted within a relatively short processing period by controlling the time of the carbonization treatment within 20min to 60min. The C02 gas used in the step of carbonization treatment may be purchased directly or prepared from a process waste gas. Preferably, the C02 in the present invention is from one or more of a boiler flue gas, a roasting kiln gas of rare earth oxalate and carbonate, and a gas produced by saponification and extraction of the magnesium bicarbonate aqueous solution. Preferably, the present invention may obtain a C02-containing gas after performing compression, purification or other processing steps by using the gas produced in several technical processes above as a raw material, thus achieving a purpose of carbonizing the magnesium hydroxide-containing solution with C02 to obtain the magnesium bicarbonate aqueous solution, while reasonably utilizing the process gas above, thus lowering carbon content and reducing emission to satisfy requirements of environment protection. All calcium-containing substances that are able to provide an alkaline environment and are removed by easily converting calcium therein into calcium sulfate are applicable to the present invention. Calcium hydroxide is used preferably, and a source of calcium hydroxide is not limited to solid powder of calcium hydroxide, and may be also calcium oxide or alkaline calcium hydroxide obtained by slaking calcium oxide obtained after roasting of calcium carbonate. From the perspectives of the processing cost of the hydrometallurgy wastewater and recycling of raw materials, the calcium-containing alkaline substance is preferably a calcium hydroxide-containing alkaline substance prepared by using rich and cheap limestone (or dolomite) and so on in the nature as raw materials. Similarly, the calcium and magnesium-containing substance refers to a mixture containing calcium hydroxide and magnesium hydroxide at the same time. The mixture may be a calcium hydroxide and magnesium hydroxide-containing mixture that is obtained by slaking a product obtained after roasting of a calcium and magnesium-containing ore or a calcium and magnesium-containing industrial waste, and may be also a calcium hydroxide and magnesium hydroxide-containing mixture that is obtained by slaking light-burneddolomite. The separation method provided by the present invention reasonably utilizes resources in all aspects, and even utilizes the solid residue obtained in Step B. In another preferred embodiment of the present invention, the solid residue obtained in Step B is acidized to prepare a calcium sulfate product, or returned into the hydrometallurgy and separation process of the rare earth ores to neutralize the acid wastewater in the hydrometallurgy wastewater so as to prepare a calcium sulfate product. The prepared calcium sulfate product with low magnesium content satisfies industrial standards of cement production and so on, and may be sold for a purpose of cement preparation and so on, thus maximizing the value of the product. In another specific embodiment, the solid residue is returned to the hydrometallurgy and separation method of the rare earth ores to neutralize the acid wastewater in the produced hydrometallurgy wastewater, or a low magnesium calcium sulfate may be also prepared, thereby implementing effective cyclic utilization of the solid residue while reducing the amount of discharged residue. By applying the carbonizing step in the preferred embodiment above, the concentration of calcium ions in the magnesium bicarbonate-containing alkaline solution obtained after the solid-liquid separation process is 0.01 g/L to 0.7 g/L, preferably 0.01 g/L to 0.4 g/L. A lower the concentration of calcium ions in the magnesium bicarbonate-containing alkaline solution will make it more difficult to cause pipeline scaling when the magnesium bicarbonate-containing alkaline solution is recycled as circulating water, thus recycling the hydrometallurgy wastewater. Since the magnesium bicarbonate-containing alkaline solution obtained in the step of recycling the hydrometallurgy wastewater is a magnesium bicarbonate aqueous solution not containing calcium ions or with extremely low content of calcium ions, the magnesium bicarbonate-containing alkaline solution may replace magnesium oxide, sodium bicarbonate or ammonium bicarbonate to be further used in the hydrometallurgy and separation step (as shown in Fig. 1) of the rare earth ores. A specific step that may reuse the magnesium bicarbonate-containing alkaline solution that contains magnesium bicarbonate includes a step of performing spraying on a waste gas produced in the acidizing process to obtain exhaust gas spray wastewater, a step of performing leaching, neutralization and impurity removal on the rare earth roasted ore obtained after sulfatizing roasting, a step of performing extraction transformation or precipitation transformation on the magnesium-containing rare earth sulfate solution, a step of saponifying the extractant in the separation extraction step, and a step of precipitating the rare earth solution to obtain the single rare earth carbonate precipitation, or the mixed rare earth carbonate, so that all steps that use water, a neutralizer, or a precipitant in the whole hydrometallurgy and separation step of the rare earth ores may use the magnesium bicarbonate-containing alkaline solution that contains magnesium bicarbonate, thereby ensuring a clean and environment-friendly production process, recycling the alkalis and the wastewater into production, reducing consumption of chemical materials, reducing production cost, implementing zero emission of wastewater, and exploring a new way of clean production and sustainable development for rare earth enterprises, and having obvious economic benefit and social benefit. In Step 2, an extractant in the priority art may be used in the process of performing the extraction transformation and/or the extraction separation on the magnesium-containing rare earth sulfate solution. A solution for saponifying the extractant in the present invention is preferably selected from, but is not limited to application of magnesium bicarbonate to saponify the organic extractant. In a preferred embodiment of the present invention, the used organic extractant is one or more of P507, P204, P229, C272, C301, C302 and C923, more preferably P507 and/or P204. The applied organic extractant is not only relatively low in cost, and but also high in extraction efficiency. Generally, the concentration of the used organic extractant is 1 mol/L to 2 mol/L, more preferably 1.0 mol/L to 1.7 mol/L. The organic extracting solvent having a concentration in the ranges above may be applied to extract rare earth elementsefficiently.

The beneficial effect of the present invention will be further described below in combination with specific embodiments.

Embodiment 1 1Kg of a Baotou mixed rare earth concentrate (50.4%) is subjected to sulfuric acid roasting, and then leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 2 g/L (based on MgO) to remove impurities. The final pH value is controlled at 4.5. Impurities including iron, phosphorus, thorium and so on are removed through precipitation. Solid-liquid separation is performed to obtain 48.9 L of a magnesium-containing rare earth sulfate solution and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 10.0 g/L (based on REO) and the recovery rate of the rare earths is 97.0%. Embodiment 2 1Kg of a Baotou mixed rare earth concentrate (REO 53.0%) is subjected to sulfuric acid roasting, and then leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 18 g/L (based on MgO) to remove impurities. The final pH value is controlled at 4.3. Impurities including iron, phosphorus, thorium and so on are removed through precipitation. Solid-liquid separation is performed to obtain 12.64 L of a magnesium-containing rare earth sulfate solution and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 41.0 g/L (based on REO) and the recovery rate of the rare earths is 97.5%. Embodiment 3 A Baotou mixed rare earth concentrate (REO 51.6%) is mixed with concentrated sulfuric acid having a concentration of 93wt% according to an ore-to-acid ratio of 1:1.4 (weight ratio) at a rate of 1 t/h, and added into a rotary kiln, and roasted continuously at 350°C. A rare earth roasted ore obtained after sulfatizing roasting is leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 10 g/L to remove impurities. The final pH value is controlled at 4.2. Solid-liquid separation is performed to obtain a magnesium-containing rare earth sulfate solution at a rate of 14.6 m 3 /h and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 34.5 g/L (based on REO) and the recovery rate of the rare earths is 97.6%. Impurity ions including iron, phosphorus, thorium and so on are precipitated into the leaching residue. Embodiment 4 2Kg of a Baotou mixed rare earth concentrate (REO 50.4%) is subjected to sulfuric acid roasting, and then leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 15 g/L (based on MgO) to remove impurities. The final pH value is controlled at 3.8. Impurities including iron, phosphorus, thorium and so on are removed through precipitation. Solid-liquid separation is performed to obtain 35 L of a magnesium-containing rare earth sulfate solution and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 28.2 g/L (based on REO) and the recovery rate of the rare earths is 98.0%. Embodiment 5 1Kg of a monazite concentrate (REO 60.9%) is subjected to sulfuric acid roasting, and then leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 25 g/L (based on MgO) to remove impurities. The final pH value is controlled at 4.4. Impurities including iron, phosphorus, thorium and so on are removed through precipitation. Solid-liquid separation is performed to obtain 13.3 L of a magnesium-containing rare earth sulfate solution and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 45.0 g/L (based on REO) and the recovery rate of the rare earths is 96.1%. Embodiment 6 1Kg of a mixed concentrate (REO 65.7%) of monazite and xenotime is subjected to sulfuric acid roasting, and then leached and neutralized by a magnesium bicarbonate aqueous solution having a concentration of 4 g/L (based on MgO) to remove impurities. The final pH value is controlled at 4.5.

Impurities including iron, phosphorus, thorium and so on are removed through precipitation. Solid-liquid separation is performed to obtain 31 L of a magnesium-containing rare earth sulfate solution and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 20.3 g (based on REO) and the recovery rate of the rare earths is 95.6%. Comparison example 1 A Baotou mixed rare earth concentrate (REO 51.6%) is mixed with concentrated sulfuric acid having a concentration of 93wt% according to an ore-to-acid ratio of 1:1.4 (weight ratio) at a rate of 1 t/h, and added into a rotary kiln, and roasted continuously at 350°C. A roasted ore is leached by an aqueous solution to extract rare earths, and then neutralization, and impurity removal are performed by using light-burned magnesium oxide. The final pH value is controlled at 4.2. Solid-liquid separation is performed to obtain a magnesium-containing rare earth sulfate solution at a rate of 15m 3/h and a leaching residue. The content of rare earths in the magnesium-containing rare earth sulfate solution is 32.5 g/L (based on REO) and the recovery rate of the rare earths is 94.5%. Impurity ions including iron, phosphorus, thorium and so on are precipitated into the leaching residue. Embodiment 7 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). Components in the magnesium-containing rare earth sulfate solution are extracted by non-saponified P507 first so as to extract middle and heavy rare earths including samarium, europium, gadolinium and so on. A raffinate is mainly a rare earth sulfate solution containing lanthanum, cerium, praseodymium and neodymium. Subsequently, extraction transformation is performed by using P204 having a concentration of 1.3 mol/L. The P204 is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 10 g/L. After 6 stages of extraction, almost all rare earths are extracted into an organic phase. Subsequently, reverse extraction is performed by using hydrochloric acid having a concentration of 6 mol/L to obtain a mixed rare earth chloride solution (REO 278g/L) and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.08 mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.07 g/L (based on REO). The mixed rare earth chloride solution obtained by the extraction transformation is extracted and separated by using a P507 organic phase having a concentration of 1.5 mol/L. The organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 10 g/L. The magnesium content in the organic phase is 0.27mol/L, and the organic phase is then subjected to exchange extraction with the rare earth solution. The content of rare earths in the organic phase is as high as 0.18 mol/L. After 56 stages of fractional extraction, praseodymium and neodymium are extracted into the organic phase. After 7 stages of counter-current reverse extraction using hydrochloric acid, a praseodymium and neodymium chloride solution is obtained. A raffinate is a lanthanum and cerium sulfate solution. The rare earth REO content in the wastewater saponified by magnesium bicarbonate is less than 0.08g/L. The lanthanum and cerium sulfate solution and a magnesium bicarbonate aqueous solution are mixed to react. Solid-liquid separation is performed to obtain a lanthanum and cerium carbonate precipitation and magnesium sulfate-containing wastewater. The rare earth precipitation yield is 99.3%. Embodiment 8 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). Extraction transformation is performed on the magnesium-containing rare earth sulfate solution by using P507 having a concentration of 1.5 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 10 g/L. After 8 stages of counter-current extraction, almost all rare earths are extracted into the organic phase. 6 stages of reverse extraction is performed by using hydrochloric acid having a concentration of 5.5 mol/L to obtain a mixed rare earth chloride solution (REO 258g/L) and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.08 mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.09 g/L (based on REO). Embodiment 9 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). Extraction transformation is performed on the magnesium-containing rare earth sulfate solution by using P204 having a concentration of 1.2 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 5 g/L. After 8 stages of counter-current extraction, almost all rare earths are extracted into the organic phase. 8 stages of reverse extraction is performed by using hydrochloric acid having a concentration of 5.8 mol/L to obtain a mixed rare earth chloride solution REO 265g/L and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.1 mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.1 g/L (based on REO). Embodiment 10 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). Extraction transformation is performed on the magnesium-containing rare earth sulfate solution by using P204 having a concentration of 1.3 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 18 g/L. After 8 stages of counter-current extraction, almost all rare earths are extracted into the organic phase. 8 stages of reverse extraction is performed by using hydrochloric acid having a concentration of 5.8 mol/L to obtain a mixed rare earth solution REO 268g/L and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.15 mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.12 g/L (based on REO). Embodiment 11 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). Fractional extraction and separation are performed directly on the magnesium-containing rare earth sulfate solution by using P507 having a concentration of 1.5 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 15 g/L. The magnesium content in the organic phase is 0.27mol/L. Saponified wastewater is obtained. The pH value of an aqueous phase is 3.5. The magnesium containing saponified organic phase is further subjected to exchange extraction with the rare earth solution. The concentration of rare earths in the organic phase is as high as 0.18 mol/L. Magnesium sulfate wastewater is obtained, and the content of rare earths in the wastewater is 0.07 g/L (based on REO). After 180 stages of fractional extraction and separation, four products including pure lanthanum sulfate, lanthanum and cerium sulfates, praseodymium and neodymium chlorides, a middle and heavy rare earth enriched product are obtained, i.e. a lanthanum sulfate solution (purity La203/REO>99.99%), a lanthanum and cerium sulfate solution (Ce02/REO>70%), a praseodymium and neodymium chloride solution (the rare earth concentration REO is 263 g/L, Nd203/REO> 75%) and the middle and heavy rare earth enriched product (Eu203/REO is

12%.) The lanthanum sulfate solution and the lanthanum-cerium sulfate solution are respectively mixed with a magnesium bicarbonate aqueous solution to react. Solid-liquid separation is performed to obtain a carbonate precipitation and magnesium sulfate wastewater, having rare earth precipitation yields of 99.1% and 99.2%, respectively. Embodiment 12 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). The magnesium-containing rare earth sulfate solution is extracted and separated directly by using a synergistic extractant (the total concentration is 1.2 mol/L and P507 accounts for 60%) of P507 and P204 saponified by a magnesium bicarbonate aqueous solution having a concentration of 15 g/L, so as to obtain four products including pure lanthanum sulfate, lanthanum and cerium sulfates, praseodymium and neodymium chlorides, a middle and heavy rare earth enriched product after 180 stages of fractional extraction and separation, i.e. alanthanum sulfate solution (purity purity La203/REO>99.99%), a lanthanum and cerium sulfate solution (purity Ce02/REO > 70%), a praseodymium and neodymium chloride solution (concentration (REO) is 269g/L, Nd203/REO>75%) and the middle and heavy rare earth enriched product (Eu203/REO is 12%.). The pH value of a magnesium bicarbonate saponified extraction aqueous phase is 3.0 and the content of rare earths in the wastewater is 0.1 g/L (based on REO). Embodiment 13 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material and the rare earth content is 34.5 g/L (based on REO). The magnesium-containing rare earth sulfate solution is precipitated by using a magnesium bicarbonate aqueous solution having a concentration of 18 g/L to obtain a mixed rare earth carbonate solution and magnesium sulfate-containing wastewater. The rare earth carbonate is further dissolved by nitric acid having a concentration of 6 mol/L, so as to obtain a mixed rare earth nitrate solution having a high concentration, and the precipitation transformation recovery rate of rare earths is 99.0%. Embodiment 14 The magnesium-containing rare earth sulfate solution in the embodiment 5 is used as a raw material and the rare earth content is 45.0g/L (based on REO). Components in the magnesium-containing rare earth sulfate solution are extracted by non-saponified C272 firstly so as to extract middle and heavy rare earths including samarium, europium, gadolinium and so on. A raffinate is mainly a rare earth sulfate solution containing lanthanum, cerium, praseodymium and neodymium. Subsequently, extraction transformation is performed by using P507 having a concentration of 1.5 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 10 g/L. After 8 stages of counter-current extraction, almost all rare earths are extracted into an organic phase. Reverse extraction is performed by using hydrochloric acid having a concentration of 5.5 mol/L to obtain a mixed rare earth chloride solution (REO 261g/L) and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.08 mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.09 g/L (based on REO). Embodiment 15 The magnesium-containing rare earth sulfate solution in the embodiment 2 is used as a raw material and the rare earth content is 41.0g/L (based on REO). The magnesium-containing rare earth sulfate solution is precipitated by using a magnesium bicarbonate aqueous solution having a concentration of 18 g/L to obtain a mixed rare earth carbonate solution and magnesium sulfate-containing wastewater. The rare earth carbonate is further dissolved by hydrochloric acid having a concentration of 6 mol/L, so as to obtain a mixed rare earth chloride solution having a high concentration, and the precipitation transformation recovery rate of rare earths is 99.1%. Embodiment 16 The magnesium-containing rare earth sulfate solution in the embodiment 1 is used as a raw material and the rare earth content is 10.0g/L (based on REO). Extraction transformation is performed on the magnesium-containing rare earth sulfate solution by using P507 having a concentration of 1.5 mol/L. An organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 10g/L. After 8 stages of counter-current extraction, almost all rare earths are extracted into the organic phase. 6 stages of reverse extraction is performed by using hydrochloric acid having a concentration of 5.5 mol/L to obtain a mixed rare earth chloride solution (REO 255g/L) and magnesium sulfate-containing wastewater. The amount of added magnesium bicarbonate is adjusted to control the acidity of an aqueous phase at a water outlet to be 0.08mol/L, and the content of rare earths in the magnesium sulfate-containing wastewater to be 0.09 g/L (based on REO). Embodiment 17 A rare earth sulfate solution having a REO content of 10 g/L is precipitated by using a magnesium bicarbonate aqueous solution having a concentration of 12 g/L to obtain a mixed rare earth carbonate precipitation and magnesium sulfate-containing wastewater. The rare earth carbonate is further dissolved by hydrochloric acid having a concentration of 6 mol/L, and transformation is performed to obtain a mixed rare earth chloride solution. The precipitation transformation recovery rate of rare earths is 99.3%. The mixed rare earth chloride solution obtained by the precipitation transformation is extracted and separated by using a P507 organic phase having a concentration of 1.5 mol/L. The organic phase is saponified by using a magnesium bicarbonate aqueous solution having a concentration of 12 g/L. The magnesium content in the organic phase is 0.27mol/L, and the organic phase is then subjected to exchange extraction with the rare earth solution. The content of rare earths in the organic phase is as high as 0.18 mol/L. After 56 stages of fractional extraction, praseodymium and neodymium are extracted into the organic phase. After 6 stages of counter-current reverse extraction using hydrochloric acid, a praseodymium and neodymium chloride solution is obtained. A raffinate is a lanthanum and cerium sulfate solution. The rare earth REO content in the wastewater saponified by magnesium bicarbonate is smaller than 0.08g/L. Embodiment 18 A magnesium-containing rare earth sulfate solution having a REO content of 25 g/L is used as a raw material. The magnesium-containing rare earth sulfate solution is precipitated by using a magnesium bicarbonate aqueous solution having a concentration of 15 g/L to obtain a mixed rare earth carbonate precipitation and magnesium sulfate-containing wastewater. The precipitation is dissolved by an acid, and transformed to obtain a mixed rare earth solution. The precipitation transformation recovery rate of rare earths is 99.4%. Embodiment 19 A magnesium-containing rare earth sulfate solution having a REO content of 45 g/L is used as a raw material. The magnesium-containing rare earth sulfate solution is precipitated by using a magnesium bicarbonate aqueous solution having a concentration of 20 g/L to obtain a mixed rare earth carbonate precipitation and magnesium sulfate-containing wastewater. The precipitation is dissolved by an acid, and transformed to obtain a mixed rare earth solution. The precipitation transformation recovery rate of rare earths is 99.5%. Comparison example 2 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material. The magnesium-containing rare earth sulfate solution is primarily separated into a SEG enriched product and a rare earth sulfate solution with little Sm by using non-saponified P507. The content of rare earths is 29 g/L (based on REO). Water is added to dilute the rare earth sulfate solution with little Sm into a concentration of about 16 g/L so as to reduce the acidity of an extraction aqueous phase. Subsequently, extraction transformation is performed by using non-saponified P204 to obtain a mixed rare earth chloride solution REO 262g/L having a high concentration and magnesium sulfate-containing wastewater. The acidity of a raffinate of the extraction transformation is 0.27mol/L. The content of rare earths is 0.25 g/L (based on REO) and the extraction transformation recovery rate of rare earths is 98.5%. The mixed rare earth chloride solution is further extracted and separated by using P507 saponified by a sodium hydroxide so as to obtain multiple rare earth chloride solutions of lanthanum and cerium, praseodymium, neodymium and so on and high salinity sodium chloride wastewater. Comparison example 3 The magnesium-containing rare earth sulfate solution in the embodiment 3 is used as a raw material. The magnesium-containing rare earth sulfate solution is precipitated by an ammonium bicarbonate solution having a concentration of 1.5 mol/L, so as to obtain mixed rare earth carbonate and ammonia-nitrogen wastewater. The rare earth carbonate is dissolved by hydrochloric acid to obtain a mixed rare earth chloride solution REO 256g/L. The precipitation transformation recovery rate of rare earths is 98%. The ammonia-nitrogen wastewater is discharged after being processed. The mixed rare earth chloride solution is extracted and separated by using P507 saponified by a sodium hydroxide so as to obtain multiple rare earth chloride solutions of lanthanum and cerium, praseodymium, neodymium and so on and high salinity sodium chloride wastewater. Embodiment 20 The magnesium sulfate-containing wastewater in the embodiment 7 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further contains sodium chloride. After being slaked, quick lime reacts with the magnesium-containing wastewater. The pH value is regulated to 10.0 to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by a processed boiler flue gas) is introduced into the slurry to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a solution containing magnesium bicarbonate (a magnesium bicarbonate containing alkaline solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate solution is 0.7 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 21 The magnesium sulfate-containing wastewater in the embodiment 7 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further contains chlorine ions. Slaked light-burned dolomite is reacted with the magnesium-containing wastewater. The pH value is regulated to 11.0 to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by a processed boiler flue gas) is introduced into the slurry to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a solution containing magnesium bicarbonate (a magnesium bicarbonate containing alkaline solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate solution is 0.62 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. The solid residue is acidized to improve the purity of calcium sulfate to be used cement production. Embodiment 22 The magnesium sulfate-containing wastewater in the embodiment 7 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further contains chloride ions. After being slaked, quick lime reacts with the magnesium-containing wastewater. The pH value is regulated to 11.5 to obtain a slurry containing magnesium hydroxide and calcium sulfate. The alkalinity of the slurry is 0.24mol/L. C02 (obtained by comprehensively recycling a boiler flue gas and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry to perform a carbonization treatment for 60 min. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. It is detected that the concentration of magnesium bicarbonate is 3.15g/L (based on MgO) and the carbonizing rate is 65.7%. Solid-liquid separation is performed on the carbonized slurry to obtain a solution containing magnesium bicarbonate (a magnesium bicarbonate containing alkaline solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate solution is 0.56 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 23 All hydrometallurgy wastewater in the embodiment 7 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further contains nitrate ions. Slaked light-burned dolomite is reacted with the magnesium-containing wastewater. The pH value is regulated to 12.5 to obtain a slurry containing magnesium hydroxide and calcium sulfate. The alkalinity of the slurry is 0.37mol/L. C02 (obtained by a processed boiler flue gas) is introduced into the slurry to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. The concentration of magnesium bicarbonate is 5.55g/L (based on MgO) and the carbonizing rate is 75.5%. Solid-liquid separation is performed on the carbonized slurry to obtain a solution containing magnesium bicarbonate (a magnesium bicarbonate containing alkaline solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate solution is 0.45 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. The solid residue is acidized to improve the purity of calcium sulfate, so as to obtain a gypsum product. Embodiment 24 All hydrometallurgy wastewater in the embodiment 7 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further contains sodium ions and nitrate ions. Slaked light-burned dolomite is reacted with the magnesium-containing wastewater. The pH value is regulated to 12.5 to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas and a burning kiln gas of rare earth oxalate and carbonate) is introduced into the slurry to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain amagnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.4 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 25 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater mainly contains magnesium sulfate and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, light-burned dolomite is added into the magnesium sulfate wastewater to react. The pH value is regulated to 12.5 to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas and a burning kiln gas of rare earth oxalate and carbonate) is introduced into the slurry to perform a carbonization treatment for 40 min. The pH value is controlled at 8.0 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.38 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate.

Embodiment 26 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. Quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 5.0 to obtain a solid and liquid mixture. Solid-liquid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 12.5 by slaked quick lime to obtain a slurry containing magnesium hydroxide and calcium sulfate. The slurry containing magnesium hydroxide and calcium sulfate is obtained.

C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a solution containing magnesium bicarbonate (a magnesium bicarbonate-containing alkaline solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.3 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 27 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 5.0 to obtain a solid and liquid mixture containing calcium sulfate. Aging is performed for 6h, and liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 12.5 by slaked quick lime to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.22 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 28 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 5.0 to obtain a solid and liquid mixture containing calcium sulfate. Aging is performed for 0.5h, and liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 12.5 by slaked quick lime to obtain a slurry containing magnesium hydroxide and calcium sulfate.

C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by

saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.27 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. The solid residue is returned to be used for neutralizing an acid wastewater in hydrometallurgy and separation of rare earth ores. Embodiment 29 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. A calcium sulfate crystal seed is added during the reaction process. The pH value is regulated to 5.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 12.5 by slaked light-burned dolomite to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain amagnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.25g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 30 All hydrometallurgy wastewater in the embodiment 16 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. Quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 4.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 11.5 by light-burned dolomite to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain amagnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.33g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. The solid residue is returned to be used for neutralizing an acid wastewater in hydrometallurgy and separation of rare earth ores. Embodiment 31 All hydrometallurgy wastewater in the embodiment 16 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 6.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 11.5 by slaked light-burned dolomite to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.3g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 32 A rare earth sulfate hydrometallurgy separation wastewater is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. Quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 9.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 11.5 by slaked light-burned dolomite to obtain a slurry containing magnesium hydroxide and calcium sulfate. The alkalinity of the slurry is 0.67mol/L.

C02 (obtained by comprehensively recycling a boiler flue gas, a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. The concentration of magnesium bicarbonate is 12.2g/L (based on MgO) and the carbonizing rate is 91.5%. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.18 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a rare earth sulfate. After being purified, the solid residue is sold at standards of commercially available gypsum.

Embodiment 33 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 10.0 to obtain a solid and liquid mixture. Liquid and solid separation is performed to obtain a filtrate. Light-burned dolomite is added into the filtrate after being slaked, so as to adjust the pH value to 11.5, so as to obtain a slurry containing magnesium hydroxide and calcium sulfate.

C02 (obtained by comprehensively recycling a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.3 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain amagnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.08 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 34 All hydrometallurgy wastewater in the embodiment 16 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 4.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 10.0 by slaked quick lime to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a burning kiln gas of rare earth oxalate and carbonate, and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain amagnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonate precipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.65 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a Baotou rare earth concentrate. Embodiment 35 All hydrometallurgy wastewater in the embodiment 14 is used as a raw material. The wastewater is mainly magnesium sulfate acid wastewater and further includes impurities including chlorine ions, sodium ions and so on. After being slaked, quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 4.0 to obtain a solid and liquid mixture containing calcium sulfate. Liquid and solid separation is performed to obtain a filtrate. The pH value of the filtrate is regulated to 11.0 by quick lime to obtain a slurry containing magnesium hydroxide and calcium sulfate. C02 (obtained by comprehensively recycling a boiler flue gas and a gas generated by saponification and extraction of a magnesium bicarbonate aqueous solution) is introduced into the slurry containing magnesium hydroxide and calcium sulfate to perform a carbonization treatment. The pH value is controlled at 7.5 to obtain a carbonized slurry. The carbonized slurry contains calcium sulfate and calcium carbonate precipitations and a magnesium bicarbonate aqueous solution. Solid-liquid separation is performed on the carbonized slurry to obtain a magnesium bicarbonate-containing alkaline solution (a magnesium bicarbonate aqueous solution) and a solid residue containing calcium sulfate and calcium carbonateprecipitations. The concentration of calcium ions in the magnesium bicarbonate-containing solution is 0.58 g/L, and the solution is returned and recycled in a hydrometallurgy and separation process of a monazite ore. Comparison example 4 All hydrometallurgy wastewater in the embodiment 12 is used as a raw material. Quick lime is reacted with the magnesium-containing wastewater. The pH value is regulated to 6.0 to 9.0. Liquid and solid separation is performed to obtain a filtrate and a waste residue. The concentration of calcium ions in the filtrate is 1.1 g/L. When the filtrate is recycled, scaling including calcium sulfate and so on is formed in a pipe line, a transmission pump and so on as temperature changes, thus seriously affecting recycling of the wastewater and greatly influencing continuous production. It may be seen from data of the embodiments above that rare earth ores hydrometallurgy separation method provided by the present invention takes a whole rare earth sulfate hydrometallurgy separation process as a main route. A sulfate roasted ore may be leached by a magnesium bicarbonate aqueous solution to extract rare earths while consuming a residual acid, and performing neutralization and removing impurities so that impurity ions including iron ions, phosphorus ions, thorium ions and so on in the rare earth ores are precipitated into a waste residue so as to remove impurities. Subsequently, hydrometallurgy wastewater is processed and comprehensively recycled, thereby forming a complete clean production process, and implementing zero emission of wastewater. By means of two steps including neutralization precipitation and carbonization purification, Mg 2+ in the rare earth sulfate hydrometallurgy wastewater is converted into a magnesium bicarbonate aqueous solution, and Ca 2+ in the wastewater is converted into calcium sulfate and a small amount of calcium carbonate, thereby thoroughly separating calcium and magnesium ions to effectively solve the problem of scaling of a pipeline, a transmission pump, an extraction tank and so on. The magnesium bicarbonate aqueous solution prepared after the carbonization may be used in processes including leaching of the rare earth roasted ore, neutralization and impurity removal, saponification, extraction and separation, rare earth precipitation and so on, thereby implementing closed loop cyclic utilization of the wastewater, implementing almost zero emission, and saving a lot of water resources. In addition, a major component of the solid residue is calcium sulfate which has stable properties, and has no influence on the environment.It may be further purified to reach standards of commercially available gypsum. Thus, the whole technical solution of the present invention has a high resource utilization rate, and significant economic and social benefits. The above are only preferred embodiments of the present invention, but are not used for limiting the present invention. For those skilled in the art, the present invention may have various alternations and changes, and any modifications, equivalent replacements, improvements and the like make within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Editorial Note 2016203453 The specification includes non sequential page numbering. description page 47 is missing

Claims

Claims 1. A hydrometallurgy and separation method of rare earth ores, wherein the method comprises: Step 1: leaching and neutralizing a rare earth roasted ore obtained by sulfatizing roasting by a magnesium bicarbonate aqueous solution to remove impurities, performing solid-liquid separation, and obtaining a magnesium containing rare earth sulfate solution and a leaching residue; and Step 2: preparing a rare earth compound product by using the magnesium-containing rare earth sulfate solution as a raw material.
2. The method according to claim 1, wherein the rare earth ore is a mineral containing at least one of monazite, xenotime, and bastnaesite.
3. The method according to claim 1, wherein a concentration of the magnesium bicarbonate aqueous solution is 2 g/L to 25 g/L based on MgO, and the pH value of the obtained magnesium-containing rare earth sulfate solution is 3.5 to 4.5 in the Step 1.
4. The method according to claim 1, wherein a rare earth content in the magnesium-containing rare earth sulfate solution is 10 g/L to 45 g/L based on Rare Earth Oxides (REO) in the Step 1.
5. The method according to claim 1, wherein the Step 2 comprises: Step 21: performing extraction transformation or precipitation transformation on the magnesium-containing rare earth sulfate solution, and obtaining a mixed rare earth solution and a first wastewater that contains magnesium sulfate; Step 22: extracting and separating the mixed rare earth solution, and obtaining a rare earth solution and a second wastewater; and Step 23: reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a third wastewater; or the Step 2 comprises:

Step 21': extracting and separating the magnesium-containing rare earth sulfate solution, and obtaining a rare earth solution and a fourth wastewater containing magnesium sulfate; and Step 22': reacting the rare earth solution with a magnesium bicarbonate aqueous solution, and obtaining a single rare earth carbonate precipitation, or a mixed rare earth carbonate precipitation and a fifth wastewater, wherein an extractant used in the step of extraction transformation or the step of extracting and separating is an organic extractant saponified by a magnesium bicarbonate aqueous solution, and a precipitant used in the step of extraction transformation is a magnesium bicarbonate aqueous solution and a rare earth content of the rare earth solution is 200 g/L to 300g/L based on REO.
6. The method according to claim 5, wherein the method further comprises a recovery processing step of hydrometallurgy wastewater generated in the hydrometallurgy and separation process, wherein the hydrometallurgy wastewater comprises at least one of the first wastewater and the fourth wastewater, and at least one of the second wastewater, the third wastewater and the fifth wastewater.
7. The method according to claim 6, wherein the recovery processing step comprises: Step A: regulating the pH value of the hydrometallurgy waterwater to 10.0 to 12.5 by using a calcium-containing alkaline substance, and obtaining a slurry containing magnesium hydroxide and calcium sulfate; and Step B: carbonizing the slurry containing magnesium hydroxide and calcium sulfate, and obtaining a magnesium bicarbonate-containing alkaline solution and a solid residue.
8. The method according to claim 7, wherein when the pH value of the hydrometallurgy wastewater is less than 2.0, the Step A comprises: Step Al: regulating the pH value of the hydrometallurgy wastewater to 4.0 to 10.0 by using the calcium-containing alkaline substance, and obtaining a solid-liquid mixture containing calcium sulfate; Step A2: performing solid-liquid separation on the solid-liquid mixture, and obtaining a filtrate containing magnesium ions; and Step A3: regulating the pH value of the filtrate containing magnesium ions to 10.0 to 12.5 by using the calcium-containing alkaline substance, and obtaining the slurry containing magnesium hydroxide and calcium sulfate.
9. The method according to claim 7, wherein the Step A further comprises a step of adding a calcium sulfate crystal seed into the hydrometallurgy wastewater, and/or performing an aging treatment on the slurry containing magnesium hydroxide and calcium sulfate.
10. The method according to claim 9, wherein a duration time of the aging treatment is 0.5 h to 6h.
11. The method according to claim 7, wherein the Step B comprises: introducing a C02 gas into the slurry containing magnesium hydroxide and calcium sulfate so as to perform a carbonization treatment, and controlling the pH value of the slurry within 7.0 to 8.0 during the carbonization treatment, and obtaining a carbonized slurry; and performing solid-liquid separation on the carbonized slurry, and obtaining the magnesium-containing alkaline solution and the solid residue.
12. The method according to claim 7 or 11, wherein the solid residue is acidized to obtain calcium sulfate, or returned into the hydrometallurgy and separation process of the rare earth ore to neutralize and process an acid wastewater in the hydrometallurgy wastewater so as to obtain calcium sulfate.
13. The method according to claim 7 or 11, wherein the concentration of calcium ions in the magnesium-containing alkaline solution is 0.01 g/L to 0.7 g/L.
14. The method according to claim 13, wherein the concentration of calcium ions in the magnesium bicarbonate-containing alkaline solution is 0.01 g/L to 0.4 g/L.
15. The method according to claim 7 or 11, wherein the magnesium containing alkaline solution is returned to the hydrometallurgy and separation method of the rare earth ore to be recycled as the magnesium bicarbonate aqueous solution.
16. The method according to claim 5, wherein the organic extractant is at leastone ofP507, P204, P229, C272, C301, C302 and C923.
17. The method according to claim 16, wherein the organic extractant is P507 and/or P204.