AU2015207917B2 - Two-stage iron removing method for solutions obtained from acid leaching of nickel oxide ores - Google Patents

Abstract

TWO-STAGE IRON REMOVING METHOD FOR SOLUTIONS OBTAINED FROM ACID LEACHING OF NICKEL OXIDE ORES A two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore, the method including: adding a garnierite slurry to a leach solution of a nickel oxide ore, stirring until the garnierite is completely dissolved and a pH value of a resulting solution reaches >1.6, conducting liquid-solid separation; heating an obtained liquid to a temperature of 130-170 0C, stirring for 1-3 hours, conducting liquid-solid separation and drying a resulting solid whereby yielding a hematite product; adding the garnierite slurry for a second time to a collected liquid, stirring for a certain time until the garnierite is completely dissolved and the pH value of a resulting solution is approximately 2, conducting liquid-solid separation; and adding magnesium oxide and an oxidant or only adding an oxidant to a resulting liquid, stirring for 0.5-4 hours, conducting liquid-solid separation, and drying the solid whereby yielding a goethite product. Solutions obtained from acid leaching of nickel oxide ores Stirred tank Liquid-solid Solid A separation Garierite slurry Liquid A The first iron Preparing silica removal [ product Liquid-solid Solid B separation Drying Liquid B Hematite 10 Stirred tank Liquid-solid Solid C Storage of product separation Liquid C Magnesium _0 Magnesium The second iron Oxidant sulfate oxide removal Separating nickel, Liquid D Liquid-solid Solid D cobalt, aluminum separating and magnesium sprto Nickel product, cobalt product Goethite and magnesium product

Description

2015207917 30M2015

TWO-STAGE IRON REMOVING METHOD FOR SOLUTIONS OBTAINED FROM ACID LEACHING OF NICKEL OXIDE ORES

FIELD OF THE INVENTION

[0001] The invention relates to a method for processing nickel ores, and more particularly to a two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore.

BACKGROUND OF THE INVENTION

[0002] Nickel oxide ore is the main resource of nickel ore. Acid leaching is one of the primary technologies for processing nickel oxide ores, and sulfuric acid is the most commonly used leaching agent. Nickel oxide ore is usually divided into a high-iron-containing ore (e.g. limonite) and a high-magnesium-containing ore (e.g. saprolite, serpentine, and garnierite). The leach solution of the nickel oxide ore obtained from atmospheric acid leaching, high pressure acid leaching or heap leaching, always contains iron, nickel, cobalt, magnesium, aluminum and other metal ions. The iron concentration is much higher than concentrations of other metal ions in the leach solution, and especially, the iron concentration in the solution from atmospheric acid leaching of the high-iron-containing ore can reach 30-50 g/L. Thus, the first step for purification and separation of the leach solution of the nickel oxide ore is iron removal.

[0003] Common methods for iron removal from leach solutions include oxidation-neutralization process, jarosite process, goethite process and hematite process. In oxidation-neutralization process, Fe2+ is oxidized to Fe3+ by an oxidant, and then an alkaline reagent is added to adjust the pH value of the solution and to precipitate Fe3+ in the form of iron hydroxide. The oxidation-neutralization process has the advantage of 1 2015207917 30 Μ 2015 simple operation, however, the iron hydroxide precipitated is a kind of colloid which makes the filtration difficult. In addition, a portion or a large amount of other metal ions, such as nickel, cobalt, magnesium and aluminum co-precipitates during iron precipitation process, resulting in losses of these metal ions. Products from jarosite process, goethite process and hematite process have excellent filtration and scrubbing performances. However, the jarosite is difficult for recycling, and the released sulfuric acid during the heap and storage of jarosite pollutes the environment, and thus, the jarosite process has been rarely used. The goethite process and the hematite process are prior methods for iron removal due that the iron precipitation products can be used and sold directly.

[0004] Goethite process has relatively low energy consumption, and is conducted at a relatively low temperature (lower than the boiling temperature of the solution) but in a relatively low acidic environment (pH 2-4) and in a solution with relatively low concentration of Fe3+ (1 g/L or so). The acidity of the leach solution of the nickel oxide ore is always high (pH< 1), and for the solution obtained from atmospheric acid leaching process, the pH value of the solution is below zero. Therefore, a large amount of alkaline reagent is needed to adjust the pH value of the solution. In addition, the iron concentration in the solution from atmospheric acid leaching process is far higher than 1 g/L, or even reaches 50 g/L. When the goethite process is adopted to remove the iron in the solution from atmospheric acid leaching process, a reducing agent is necessitated to reduce Fe3+ to Fe2+ firstly so as to maintain a relatively low Fe3+ concentration (e.g.<lg/L), an oxidant is then added slowly to oxidize Fe2+ to Fe3+, and finally Fe3+ is slowly hydrolyzed to goethite and precipitated from the solution. The above process not only requires a large amount of the oxidant and the reducing agent, but also prolongs the time for iron precipitation. Thus, for the leach solution with high iron concentration, the goethite process is rarely adopted to remove iron.

[0005] The hematite process is usually carried out at a temperature of approximately 250°C and a pressure of approximately 4MPa. Iron can be precipitated in the form of 2 2015207917 30 Μ 2015 hematite even in a highly acidic environment, and thus the iron removal rate is relatively high. However, the method has high energy consumption and necessitates an autoclave made of materials with high temperature resistance, high pressure resistance and corrosion resistance, resulting in high equipment cost and operation cost. In recent years, it has been proposed in some patents to precipitate the hematite at 120-200°C where the acid corrosion on the device is largely decreased, so that the autoclave with cheap cost and simple operation can be utilized thereby decreasing the equipment investment and the maintenance cost; furthermore, the acid released from the iron precipitation can be recycled thereby largely decreasing the acid consumption and the processing cost. Taken the patent publication No. CN101392321A as an example, the method for precipitating the hematite at 120-200°C is disclosed, however, such method requires to add the carbon-containing reducing agent to carry out microwave reduction roasting on the mineral before leaching and iron precipitation procedures and is therefore not suitable for direct precipitation of the iron in solutions from atmospheric leaching of nickel oxide ores.

[0006] In addition, the hematite precipitation at 120-200°C generally requires that the pH value of the solution is greater than 1. Similar to the goethite process, it is needed to decrease the acidity of the leach solution before iron removal process. Various methods to neutralize the residual acid in the leach solution of the nickel oxide ore have been proposed by domestic and foreign scholars in recent years. Some alkaline substances are utilized as neutralizing agents, for example, patent publication No. WO2013120131A1 has mentioned to neutralize the acid in the heap leaching solution by limestone or calcium carbonate to precipitate the iron in the form of goethite. The purpose for adjusting the acidity of the leach solution can be reached by this method, but the residual acid in the leach solution cannot be recycled. It has been proposed in some patents to use the high-magnesium-containing ore to neutralize the residual acid in the solution, such as the patent publication Nos. CN102212684A, CN101418379A, CN102286661A, 3 2015207917 30 Μ 2015 W02001032944A1, and AU2011218755A1 that adopt the high-magnesium-containing ore to neutralize the residual acid of the leach solution of the high-iron-containing ore. The pH value of the leach solution is improved by the method, however, the iron precipitation product is jarosite, which is difficult for recycling and is a pollutant to environment.

[0007] Patent publication Nos. CN101139656A, W02006084335A1, W02006029499A1 propose to utilize the residual acid in the leach solution or the acid released from the iron precipitation in the autoclave to leach high-magnesium-containing serpentine or saprolite ores, and to precipitate the iron in the leach solution in the form of iron oxide simultaneously. However, the method mentioned in the above patents is unable to completely remove the iron in the leach solution, a certain amount of iron remains in the solution, and the ore with high magnesium content is not totally leached. For example, in the method taught by the Patent Publication No. CN101139656A, the concentration of the residual iron reaches 1.5 g/L, and the extractions of nickel and cobalt of the saprolite reach 70% and 80%, respectively, which means the saprolite is not completely dissolved. For the method disclosed in Patent Publication No. W02006084335A1, the concentration of residual iron is relatively low, within the range of 0.3-0.8 g/L, but the time to leach saprolite is very long, approximately 10 hours, resulting in the high energy consumption. The iron removal rate in the method disclosed in the Patent Publication No. W02006029499A1 only reaches 90% leaving 7-10% of iron not totally removed. The residual iron will disturb the subsequent separation of nickel from cobalt, decrease the separation rate of nickel from cobalt, and result in incomplete separation thereof. In addition, Patent Publication No. AU2007100902A4 proposed to add a nickel ore material to the autoclave to neutralize the acid released from the hematite precipitation, but it doesn’t mention the types and phases of the leach residue, the method for preventing the influences of the leach residue and the hematite product on autoclave scaling, or the method for the separation of leach residues from hematite products. Actually, there is still 4 2015207917 30 Μ 2015 a plurality of technical problems to be tackled for the above methods, for example, how to avoid the scale formation on the autoclave wall and the iron precipitation product mixed in the scale, how to prevent the losses of nickel and cobalt during iron precipitation process, how to ensure complete dissolution of the high-magnesium -containing ore, how to avoid the formation of the basic ferric sulfate that is difficult to treat and recycle and the iron precipitation product that has poor filtration performance, how to completely separate the iron precipitation product from the leach residue of the high-magnesium-containing ore, and how to totally remove the iron from the leach solution, etc. However, the above published patents do not provide any effective means to tackle such technical problems.

[0008] Patent Publication No. CN103060549A that has been filed by the present applicant has made improvement on the above processes, and proposed to add the high-magnesium-containing ore in batches to gradually neutralize the residual acid of the leach solution. Such method is able to effectively control the pH value of the solution, the precipitation speed of iron, and the dissolution rate of the high-magnesium-containing ore, the residual acid of the leach solution and the acid produced from the iron precipitation are fully utilized, while complete iron precipitation and complete dissolution of the high-magnesium-containing ore are realized. The obtained hematite product is easily filtrated, almost no loss of nickel or cobalt remains in the product, and the iron precipitation product can be effectively separated from the leach residue of the high-magnesium-containing ore. But this method has strict requirement on the amount of the added high-magnesium-containing ore and the pH value of the leach solution. When the pH value, the iron concentration of the solution, or the mineral composition of the high-magnesium-containing ore changes, it is required to adjust and change the addition amount and the addition time of the high-magnesium- containing ore, which makes the operation somewhat troublesome. 5 2015207917 30 Μ 2015

SUMMARY OF THE INVENTION

[0009] In view of the above-described problems, it is one objective of the invention to provide a two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore. The method does not require expensive and sophisticated autoclave and realizes complete iron removal in relatively moderate conditions. Not only are the hematite and the goethite that can be directly for sale acquired by the method, but also the residual acid in the leach solution and the acid released from the iron precipitation process are recycled. Furthermore, no additional reagent is added during the iron removal process, and no loss of nickel, cobalt, magnesium, or aluminum in the leach solution is resulted.

[0010] A two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore, comprises: [0011] 1) adding a garnierite slurry to a leach solution of a nickel oxide ore, stirring for a certain time until the garnierite is completely dissolved and a pH value of a resulting solution reaches >1.6, conducting liquid-solid separation whereby obtaining a solid A and a liquid A; [0012] 2) heating the liquid A to 130-170°C, stirring for 1-3 hours, conducting liquid-solid separation whereby obtaining a solid B and a liquid B, and collecting and drying the solid B whereby yielding a hematite product; [0013] 3) adding the garnierite slurry for a second time to the liquid B, stirring for a certain time until the garnierite is completely dissolved and the pH value of a resulting solution is slightly lower than 2 or >2, conducting liquid-solid separation whereby obtaining a solid C and a liquid C; [0014] 4) adding magnesium oxide and an oxidant to the liquid C when the pH value of the liquid C is slightly lower than 2, or adding an oxidant to the liquid C when pH >2; 6 2015207917 30M2015 stirring for 0.5-4 hours, conducting liquid-solid separation whereby yielding a solid D and a liquid D, and collecting and drying the solid D whereby yielding a goethite product; and [0015] 5) introducing the liquid D to later purification and separation procedures and separating nickel, cobalt, aluminum and magnesium, and combining the solid A and the solid C for preparing a silica product.

[0016] The leach solution of the nickel oxide ore in step 1) is the solution obtained from leaching of the nickel oxide ore by the common methods, such as the atmospheric acid leaching, the high pressure acid leaching and the heap leaching. Preferably, the leaching agent in the above methods is sulfuric acid. Generally, the iron concentration in the leach solution of the nickel oxide ore is 3-50 g/L. When the iron concentration is greater than 50 g/L, the method of the invention is also applicable for removing iron. When the iron concentration is lower than 3 g/L, the leach solution is often diluted and the goethite process is then adopted to remove iron. In this step, a preferable pH value of the solution after the addition and dissolution of the gamierite slurry is between 1.6 and 2.0, the range of which is much beneficial for the hematite precipitation in step 2).

[0017] After the treatment of step 2), a majority of Fe3+ in the liquid A is precipitated in the form of hematite, and the obtained liquid B has a concentration of Fe3+ approximately to or lower than 1 g/L. On the other aspect, the acidity of the liquid B increases (i. e. the pH value decreases) after the iron precipitation of step 2) due to the acid released from the hematite precipitation, and it is required to raise the pH value of the liquid B to be greater than 2 to conduct the goethite precipitation. Therefore, the gamierite slurry is added for the second time in step 3) to consume the residual acid of the liquid B and increase the pH value of the liquid B.

[0018] In step 3), the pH value of the liquid C is preferably controlled within the range of 2- 4 in order to facilitate the precipitation of the goethite. In this step, it is required that 7 2015207917 30 Μ 2015 the gamierite added for the second time completely reacts with the residual acid of the liquid B, that is, the gamierite added for the second time is totally dissolved. When the pH value of the solution obtained from the complete dissolution of the gamierite and the subsequent liquid-solid separation is slightly lower than 2 (i.e. approximately to 2), the pH value is often adjusted to be >2 by adding magnesium oxide rather than by adding the gamierite slurry. The required magnesium oxide is not great, and magnesium oxide can be recycled from the later purification and separation procedures, thereby basically not increasing the production cost. On the other aspect, if the pH value of the solution is adjusted to be >2 by adding an overdose of the gamierite slurry in step 3), there is no need to add magnesium oxide in step 4), but a partial of the gamierite slurry may be incompletely dissolved. The incompletely dissolved gamierite and the dissolution residue coexist in the solid C, which not only decreases the dissolution rate of the gamierite, but also makes the treatment of the solid C much difficult. The addition of magnesium oxide in step 4) to adjust the pH value of the liquid C to be >2 will not introduce the solid residue because the amount of the added magnesium oxide is not great and the added magnesium oxide is dissolved quickly and completely. The solid C can also be directly used to recover the silica product, thereby largely decreasing the difficulty for processing the solid C and effectively avoiding the incomplete dissolution of the gamierite. The pH value of the solution of slightly lower than 2 herein refers to the pH value of between 1.9 and 2.0. In this step, when the gamierite slurry added for the second time completely reacts with the residual acid of the liquid B and the pH value of the solution is >2, since the pH value is high enough for the goethite precipitation, it is not required to add additional magnesium oxide in step 4) to adjust the pH value of the liquid C. Preferably, the pH value of the solution is controlled at between 2 and 2.2, the range of which is not only helpful for the goethite precipitation but also beneficial for reducing the production cost.

[0019] Stirring in step 1), step 3), and step 4) is performed at a temperature of between 8 2015207917 30 Μ 2015 40°C and boiling temperatures of the solutions.

[0020] In the above step 4), the purpose of the addition of magnesium oxide is to adjust the pH value of the liquid C to be >2, and preferably to adjust the pH value of the liquid C to be between 2 and 2.2. In this step, the oxidant is hydrogen peroxide, oxygen, or air, and preferably, the air is adopted as the oxidant. The amount of the added oxidant is the same as that in the prior art, and is generally 0.5-2.5 times the mole number of Fe2+.

[0021] In the above method, the garnierite is the magnesium-rich silicate ore containing nickel, that is the high-magnesium-containing nickel oxide ore, and preferably, the magnesium content is within a range of 5- 25 wt. %, and a solid content of the garnierite slurry is between 10 wt. % and 40 wt. %.

[0022] In step 5), magnesium oxide obtained from purification and separation procedures is returned to step 4) for utilization, or directly for sale as a product.

[0023] In step 1) of the method, when the pH value of the leach solution of the nickel oxide ore is >1.6, step 1) is deleted, and the steps 2)-5) are directly conducted.

[0024] Compared with the prior art, the method of the invention has the following advantages: [0025] 1. A majority of iron is firstly removed by the hematite precipitation, and the remaining iron is removed by the goethite precipitation. The two-stage iron removal ensures the iron completely removed, and the iron is transformed into the hematite and the goethite that can be directly for sale. The iron in the solution obtained by the atmospheric acid leaching, the high pressure acid leaching, and the heap leaching can be removed using the method of the invention.

[0026] 2. When the high-magnesium-containing ore is utilized to neutralize the residual acid in the leach solution, the iron precipitation and the dissolution of the high-magnesium-containing ore are carried out separately, so that the subsequent separation of 9 2015207917 30 Μ 2015 the iron precipitation product from the leach residue of the high-magnesium-containing ore, the autoclave scaling and the iron precipitation product mixed in the scale are avoided, the iron precipitation process is prevented from being disturbed by the magnesium and aluminum ions and the amorphous silica residue. By elimination of the above disturbances and effective adjustment of the pH value of the solution, the formation of the environmentally polluting products (basic ferric sulfate, jarosite, etc.) and the byproducts with low crystallinity during iron precipitation is prevented, thereby making the types of the iron precipitation product single (only the hematite and the goethite), obtaining iron precipitation product with higher crystallinity, increasing the rate for iron precipitation, and realizing complete iron precipitation. In addition, since the iron precipitation product has the high crystallinity, the filtration performance of the iron precipitation product is largely improved, and the losses of nickel, cobalt, magnesium, and aluminum ions are almost decreased to zero.

[0027] 3. The garnierite are adopted twice to neutralize the residual acid of the leach solution and the acid released from the hematite precipitation, so that the acid consumed during the leaching process of the nickel oxide ore is fully recovered. In addition, the garnierite is leached in the absence of any acidic leaching agent. Therefore, the acid consumption and the cost for the whole leaching process of the nickel oxide ore are largely decreased. Compared with the prior arts adopting the high-magnesium-containing ore for neutralizing the residual acid of the leach solution, the method of the invention is able to not only meet the requirement of the pH value for the iron precipitation, but also ensure the complete dissolution of the high-magnesium-containing ore.

[0028] 4. The first iron removing step is carried out in relatively moderate conditions (130-170°C), so that the high priced and highly anti-corrosive autoclave is not required. No additional reagent is necessitated during the iron removing process. After the complete dissolution of the added garnierite ore, the nickel, cobalt, magnesium, and aluminum ions enter into the leach solution and are separated in the subsequent 10 2015207917 30 Μ 2015 purification procedures, while the iron entering into the leach solution is transformed into hematite and goethite via the iron removal steps. Because a majority of iron is removed in the first iron removing step and the concentration of Fe3+ is approximately or slightly lower than 1 g/L, the additional reducing reagent is not required when the second iron removing step (goethite process) is conducted. A very small amount of or even no neutralizing reagent, magnesium oxide is required in the second iron removing step, and magnesium oxide can be recycled from later separation procedures. Neither is the acidic liquor discharged, nor are the basic ferric sulfate and jarosite produced, thereby avoiding the environmental pollution. Therefore, the cost of the whole process of iron removal is low.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a process flow diagram of a two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] For further illustrating the invention, experiments detailing a two-stage iron removing method for a leach solution of a nickel oxide ore are described below combined with the drawings.

Example 1 [0031] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was provided, which had the concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 30.4 g/L, 0.5 g/L, 1.05 g/L, 0.095 g/L, 4.3 g/L, and 1.89 g/L and had the pH value of 0.38. An 11 2015207917 30 Μ 2015 aqueous slurry of garnierite having a solid content of 30 wt. % and contents of Fe, Ni, Co, Mg, and A1 of 4.8 wt. %, 1.9 wt. %, 0.04 wt. %, 24.1 wt. %, 3.7 wt. % was added to the original leach solution. The addition of the aqueous slurry of the garnierite was 2.5 times the volume of the original leach solution. The resulting mixture was heated to 90°C and stirred for 1 hour so as to completely dissolve the garnierite. Thereafter, the liquid-solid separation was performed, and a solid A and a liquid A were yielded.

[0032] 2) The liquid A was heated to 160°C and then was stirred for 1.5 hours. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0033] 3) The garnierite slurry was added for a second time to the liquid B (the solid content of the garnierite slurry was the same as that of step 1), and the addition of the garnierite slurry was 25 percent of the volume of the liquid B). The resulting mixture was thereafter heated to 90°C and stirred for 45 min to completely dissolve the garnierite added for the second time. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0034] 4) Magnesium oxide powder was added to the liquid C to make a concentration thereof in the liquid C to be 0.1 g/L and air was introduced to the liquid C at a flow rate of 0.01 L/min, and the resulting mixture was then stirred at a temperature of 80°C for 2 hours. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0035] 5) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid A obtained from step 1) and the solid C obtained from step 3) were combined and dried to produce a silica product.

[0036] Flow chart of the whole process is illustrated in FIG 1. 12 2015207917 30 Μ 2015 [0037] It was determined that the liquid A had the pH value of 1.9 and concentrations of Fe3+ and Fe2+of 13.3 g/L and 0.58 g/L; the liquid B had the pH value of 1.6 and concentrations of Fe3+ and Fe2+ of 1.03 g/L and 0.52 g/L; the liquid C had the pH value of 2.1 and concentrations of Fe3+ and Fe2+ of 1.45 g/L and 0.74 g/L; and the liquid D had a concentration of Fe3+ of 20 ppm, and Fe2+ was not detected. A total iron removal rate exceeded 99 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 98 wt. % and 97 wt. %, respectively.

Example 2 [0038] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was provided, which had concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 42.4 g/L, 2.5 g/L, 1.24 g/L, 0.15 g/L, 3.3 g/L, 1.1 g/L and had a pH value of -0.03. An aqueous slurry of garnierite having a solid content of 20 wt. % and contents of Fe, Ni, Co, Mg, and A1 of 3.2 wt. %, 1.19 wt. %, 0.05 wt. %, 19.1 wt. %, 4.9 wt. % was added to the original leach solution. The addition of the aqueous slurry of the garnierite was 3 times the volume of the original leach solution. The resulting mixture was stirred at 100°C for 0.5 hour so as to completely dissolve the garnierite. Thereafter, the liquid-solid separation was performed, and a solid A and a liquid A were yielded.

[0039] 2) The liquid A was heated to a temperature of 140°C and was stirred for 2 hours. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0040] 3) The garnierite slurry was added for a second time to the liquid B (the solid content of the garnierite slurry was the same as that of step 1), and the addition of the garnierite slurry was 2 times the volume of the liquid B). The resulting mixture was 13 2015207917 30 Μ 2015 thereafter stirred at a temperature of 100°C for 0.5 hour to completely dissolve the garnierite added for the second time. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0041] 4) Magnesium oxide powder was added to the liquid C to make a concentration thereof in the liquid C to be 0.2 g/L and hydrogen peroxide was introduced to the liquid C at a flow rate of 0.05 L/min, and the resulting mixture was then stirred at a temperature of 60°C for 0.5 hour. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0042] 5) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid A obtained from step 1) and the solid C obtained from step 3) were combined and dried to produce a silica product.

[0043] It was determined that the liquid A had the pH value of 1.9 and concentrations of Fe3+ and Fe2+of 14.5 g/L and 0.78 g/L; the liquid B had the pH value of 1.4 and concentrations of Fe3+ and Fe2+ of 1.05 g/L and 0.72 g/L; the liquid C had the pH value of 2.0 and concentrations of Fe3+ and Fe2+ of 1.39 g/L and 0.8 g/L; and the liquid D had a concentration of Fe3+ of 30 ppm, and Fe2+ was not detected. A total iron removal rate exceeded 98 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 99 wt. % and 98 wt. %, respectively.

Example 3 [0044] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was 14 2015207917 30 Μ 2015 provided which had concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 19.4 g/L, 3.1 g/L, 1.0 g/L, 0.11 g/L, 8.3 g/L, 2.1 g/L and had a pH value of 0.73. An aqueous slurry of garnierite having a solid content of 40 wt. % and contents of Fe, Ni, Co, Mg, and A1 of 1.5 wt. %, 1.09 wt. %, 0.02 wt. %, 13.4 wt. %, 5.9 wt. % was added to the original leach solution. The addition of the aqueous slurry of the garnierite was 1.5 times the volume of the original leach solution. The resulting mixture was stirred at 60°C for 2 hours so as to completely dissolve the garnierite. Thereafter, the liquid-solid separation was performed, and a solid A and a liquid A were yielded.

[0045] 2) The liquid A was heated to a temperature of 130°C and was stirred for 3 hours. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0046] 3) The garnierite slurry was added for a second time to the liquid B (the solid content of the garnierite slurry was the same as that of step 1), and the addition of the garnierite slurry was 50 percent of the volume of the liquid B). The resulting mixture was thereafter stirred at a temperature of 40°C for 2 hours to completely dissolve the garnierite added for the second time. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0047] 4) Magnesium oxide powder was added to the liquid C to make a concentration thereof in the liquid C to be 0.25 g/L and oxygen was introduced to the liquid C at a flow rate of 0.01 L/min, and the resulting mixture was then stirred at a temperature of 70°C for 3 hours. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0048] 5) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid A obtained from step 1) and the solid C obtained from step 3) were combined and dried to produce a silica 15 2015207917 30 Μ 2015 product.

[0049] It was determined that the liquid A had the pH value of 2.0 and concentrations of Fe3+ and Fe2+of 11.3 g/L and 1.2 g/L; the liquid B had the pH value of 1.8 and concentrations of Fe3+ and Fe2+ of 0.97 g/L and 1.09 g/L; the liquid C had the pH value of 2.0 and concentrations of Fe3+ and Fe2+ of 1.09 g/L and 1.28 g/L; and the liquid D had a concentration of Fe3+ of 25 ppm, and Fe2+ was not detected. A total iron removal rate exceeded 96 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 97 wt. % and 97 wt. %, respectively.

Example 4 [0050] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was provided which had concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 7.4 g/L, 1.3 g/L, 0.95 g/L, 0.09 g/L, 15.3 g/L, 5.1 g/L and had a pH value of 0.83. An aqueous slurry of garnierite having a solid content of 30 wt. % and contents of Fe, Ni, Co, Mg, and A1 of 2.4 wt. %, 1.29 wt. %, 0.05 wt. %, 20.4 wt. %, 10.9 wt. % was added to the original leach solution. The addition of the aqueous slurry of the garnierite was the same volume as that of the original leach solution. The resulting mixture was stirred at 70°C for 1.5 hours so as to completely dissolve the garnierite. Thereafter, the liquid-solid separation was performed, and a solid A and a liquid A were yielded.

[0051] 2) The liquid A was heated to a temperature of 170°C and was stirred for 1 hour. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0052] 3) The garnierite slurry was added for a second time to the liquid B (the solid 16 2015207917 30 Μ 2015 content of the garnierite slurry was the same as that of step 1), and the addition of the garnierite slurry was 50 percent of the volume of the liquid B). The resulting mixture was thereafter stirred at a temperature of 60°C for 1 hour to completely dissolve the garnierite added at the second time. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0053] 4) Magnesium oxide powder was added to the liquid C to make a concentration thereof in the liquid C to be 0.25 g/L and air was introduced to the liquid C at a flow rate of 0.015 L/min, and the resulting mixture was then stirred at a temperature of 100°C for 1.5 hours. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0054] 5) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid A obtained from step 1) and the solid C obtained from step 3) were combined and dried to produce a silica product.

[0055] It was determined that the liquid A had the pH value of 2.0 and concentrations of Fe3+ and Fe2+of 5.1 g/L and 1.1 g/L; the liquid B had the pH value of 1.7 and concentrations of Fe3+ and Fe2+ of 0.98 g/L and 0.97 g/L; the liquid C had the pH value of 1.95 and concentrations of Fe3+ and Fe2+ of 0.96 g/L and 1.02 g/L; and the liquid D had a concentration of Fe3+ of 4 ppm, and Fe2+ was not detected. A total iron removal rate exceeded 99 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 97 wt. % and 98 wt. %, respectively.

Example 5 17 2015207917 30 Μ 2015 [0056] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was provided which had concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 14.2 g/L, 0.83 g/L, 1.05 g/L, 0.04 g/L, 23.3 g/L, 6.3 g/L and had a pH value of 1.7. The liquid A was heated to a temperature of 150°C and was stirred for 2 hours. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0057] 2) An aqueous slurry of garnierite having a solid content of 25 wt. % and contents of Fe, Ni, Co, Mg, and A1 of 1.94 wt. %, 1.29 wt. %, 0.05 wt. %, 8.4 wt. %, 6.9 wt. % was added to the liquid B. The addition of the aqueous slurry of the garnierite was the 1.25 times the volume of the liquid B. The resulting mixture was thereafter stirred at a temperature of 90°C for 0.5 hour to completely dissolve the garnierite. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0058] 3) Magnesium oxide powder was added to the liquid C to make a concentration thereof in the liquid C to be 0.18 g/L and air was introduced to the liquid C at a flow rate of 0.009 L/min, and a resulting mixture was then stirred at a temperature of 80°C for 1.5 hours. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0059] 4) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid C obtained from step 2) was collected and dried to produce a silica product.

[0060] Flow chart of the whole process is illustrated in FIG. 1.

[0061] It was determined that the liquid B had the pH value of 1.5 and concentrations of Fe3+ and Fe2+of 1.39 g/L and 0.71 g/L; the liquid C had the pH value of 2.05 and concentrations of Fe3+ and Fe2+of 1.16 g/L and 1.82 g/L; and the liquid D had a concentration of Fe3+ of 15 ppm, and Fe2+ was not detected. A total iron removal rate 18 2015207917 30 Μ 2015 exceeded 99 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 99 wt. % and 97 wt. %, respectively.

Example 6 [0062] 1) An original solution from sulfuric acid leaching of a nickel oxide ore was provided which had concentrations of Fe3+, Fe2+, Ni2+, Co2+, Mg2+, and Al3+ of 11.9 g/L, 2.83 g/L, 1.12 g/L, 0.08 g/L, 20.3 g/L, 2.3 g/L and had a pH value of 0.92. An aqueous slurry of garnierite having a solid content of 10 wt.% and contents of Fe, Ni, Co, Mg, and A1 of 2.4 wt.% , 1.29 wt.% , 0.05 wt.% , 20.4 wt.% , 10.9 wt.% was added to the original leach solution. The addition of the aqueous slurry of the garnierite was 2 times the volume of the original leach solution. The resulting mixture was stirred at 70°C for 2 hours so as to completely dissolve the garnierite. Thereafter, the liquid-solid separation was performed, and a solid A and a liquid A were yielded.

[0063] 2) The liquid A was heated to a temperature of 170°C and was stirred for 1.5 hours. After that, the liquid-solid separation was conducted, and a solid B and a liquid B were yield. The solid B was collected and dried to obtain a hematite product.

[0064] 3) The garnierite slurry was added for a second time to the liquid B (the solid content of the garnierite slurry was the same as that of step 1), and the addition of the garnierite slurry was 1.5 times the volume of the liquid B). The resulting mixture was thereafter stirred at a temperature of 90°C for 2 hours to completely dissolve the garnierite added for the second time. The liquid-solid separation was then performed to yield a solid C and a liquid C.

[0065] 4) Air was introduced to the liquid C at a flow rate of 0.009 L/min, and the 19 2015207917 30 Μ 2015 resulting mixture was then stirred at a temperature of 85°C for 1.5 hours. The solid-liquid separation was conducted, and a solid D and a liquid D were obtained. The solid D was collected and dried to obtain a goethite product.

[0066] 5) The liquid D was introduced to later purification and separation procedures to separate nickel, cobalt, aluminum and magnesium. Magnesium oxide acquired from the separation procedure was returned to step 4) for recycling. The solid A obtained from step 1) and the solid C obtained from step 3) were combined and dried to produce a silica product.

[0067] It was determined that the liquid A had the pH value of 2.0 and concentrations of Fe3+ and Fe2+of 5.4 g/L and 1.04 g/L; the liquid B had the pH value of 1.6 and concentrations of Fe3+ and Fe2+ of 1.02 g/L and 0.96 g/L; the liquid C had the pH value of 2.2 and concentrations of Fe3+ and Fe2+ of 1.12 g/L and 1.23 g/L; and the liquid D had a concentration of Fe3+ of 6 ppm, and Fe2+ was not detected. A total iron removal rate exceeded 99 wt. %. Main components of both the solid A and the solid C were Si and O. The solid B and the solid D were the hematite and the goethite, respectively. Ni, Co, Mg, A1 were not detected in the solid B and the solid D. The extractions of nickel and cobalt were 97 wt. % and 98 wt. %, respectively. 20

Claims (9)

1. TWO-STAGE IRON REMOVING METHOD FOR SOLUTIONS OBTAINED FROM ACID LEACHING OF NICKEL OXIDE ORES CLAIMS

   1. A two-stage iron removing method for a solution obtained from acid leaching of a nickel oxide ore, the method comprising the following steps: 1) adding a garnierite slurry to a solution obtained from acid leaching of a nickel oxide ore, stirring for a certain time until the garnierite is completely dissolved and a pH value of a resulting solution reaches >1.6, conducting liquid-solid separation whereby obtaining a solid A and a liquid A; 2) heating the liquid A to a temperature of 130-170°C, stirring for 1-3 hours, conducting liquid-solid separation whereby obtaining a solid B and a liquid B, and collecting and drying the solid B whereby yielding a hematite product; 3) adding the garnierite slurry for a second time to the liquid B, stirring for a certain time until the garnierite is completely dissolved and the pH value of a resulting solution is slightly lower than 2 or >2, conducting liquid-solid separation whereby obtaining a solid C and a liquid C; 4) adding magnesium oxide and an oxidant to the liquid C when the pH value of the liquid C is slightly lower than 2, or adding an oxidant to the liquid C when pH >2; stirring for 0.5-4 hours, conducting liquid-solid separation whereby yielding a solid D and a liquid D, and collecting and drying the solid D whereby yielding a goethite product; and 5) introducing the liquid D to later purification and separation procedures and separating nickel, cobalt, aluminum and magnesium, and combining the solid A and the solid C for preparing a silica product.
2. 2. The method of claim 1, wherein in step 1), the garnierite slurry is added and stirred to adjust the pH value of the solution to be 1.6-2.0.
3. 3. The method of claim 1, wherein in step 1) and step 3), a solid content of the garnierite slurry is 10-40 wt. %.
4. 4. The method of claim 1, wherein in step 3), the pH value of the solution being “slightly lower than 2” means the pH value is 1.9-2.
5. 5. The method of claim 1, wherein in step 3), the pH value of the solution being “>2” means the pH value is 2-2.2.
6. 6. The method of claim 1, wherein the stirring in step 1), step 3), and step 4) are carried out at a temperature of between 40°C and boiling temperatures of the solutions.
7. 7. The method of claim 1, wherein in step 4) the magnesium oxide is added to adjust the pH value of the liquid C to be >2.
8. 8. The method of claim 1, wherein in step 4), the addition of the oxidant is 0.5-2.5 times a mole number of Fe2+.
9. 9. The method of claim 1, wherein in step 1), when the pH value of the solution obtained from acid leaching of the nickel oxide ore is >1.6, step 1) is deleted, and steps 2)-5) are directly conducted.