JP7090877B2 - How to recover valuable metals - Google Patents

Description

The present invention relates to a method for recovering a valuable metal, which can effectively separate impurities such as phosphorus and tin from solid waste containing valuable metals such as nickel and intermediate waste liquid, and can easily recover the valuable metal.

Valuable metals such as nickel, copper and zinc are contained in the waste liquid and waste sludge discharged from plating factories and the like. Therefore, in order to recover valuable metals from such waste liquids and waste sludge, separation methods such as a neutralization coagulation precipitation method, a solvent extraction method, and an ion exchange resin method have been studied.

For example, Patent Document 1 discloses a method for separating nickel from nickel sludge. This separation method includes a leaching step in which a sulfuric acid solution is added to nickel sludge to adjust the pH to 4 to 6 to solid-liquid separation into a precipitate and a leaching solution, and a concentration step of concentrating the leaching solution obtained in the leaching step. It has a cooling step of cooling the concentrated solution obtained in the concentration step to crystallize the crystals of nickel sulfate, and a crystallization step of recovering the crystals of nickel sulfate by solution separation.

Japanese Unexamined Patent Publication No. 2016-56434

In the conventional nickel separation method described in Patent Document 1 described above, nickel sulfate crystals are obtained through a leaching step, a concentration step, a cooling step and a crystallization step. For this reason, the number of steps for obtaining nickel sulfate crystals is large, the recovery of valuable metals is complicated, and it takes a considerable amount of time for concentration and cooling to crystallize the crystals, resulting in poor recovery efficiency. Furthermore, nickel sludge contains impurities such as phosphorus and tin, and it is difficult to easily reduce the content of such impurities, and therefore the content of valuable metals could not be sufficiently improved. .. In order to obtain nickel oxide, a firing step of firing nickel sulfate at a high temperature of about 1000 ° C. is required.

Therefore, an object of the present invention is to provide a method for recovering a valuable metal, which can reduce the content of impurities, improve the content of the valuable metal, and recover the valuable metal by a simple method. ..

In order to achieve the above object, the method for recovering a valuable metal of the present invention adds an inorganic acid to a waste containing a valuable metal and separates it into a solution of the valuable metal and a precipitate of impurities containing phosphorus and tin. A separation step, a valuable metal oxalate production step in which oxalic acid is added to the valuable metal solution to form a precipitate of the valuable metal oxalate, and a valuable metal oxalate generation step by firing the valuable metal oxalate. It includes a firing step of producing metal oxides.

Therefore, the valuable metal can be recovered by a simple combination of a separation step, an oxalate production step, and a calcination step. Further, in the separation step, the valuable metal becomes a salt of an inorganic acid and is present in the solution, while impurities are contained in a large amount in the precipitate, so that the precipitate is separated from the solution by the separation operation. In the oxalate production step, valuable metals rapidly react with oxalic acid to form oxalate and precipitate, while impurities are difficult to react with oxalic acid and tend to remain in the solution. Therefore, a precipitate of valuable metal oxalate can be obtained by the separation operation.

In the firing step, the oxalate of the valuable metal is oxidized, and a calcined product containing an oxide of the target valuable metal can be obtained at a low temperature of 350 ° C. Therefore, the content of impurities in the fired product can be reduced and the content of valuable metals can be increased.

According to the method for recovering a valuable metal of the present invention, the content of impurities can be reduced, the content of the valuable metal can be improved, and the valuable metal can be recovered by a simple method.

The graph which shows the relationship between the leaching rate (mass%) and pH about Example 1. FIG. The graph which shows the relationship between the leaching rate (mass%) and pH about Example 2. FIG. The graph which shows the relationship between the leaching rate (mass%) and pH about Example 3. FIG. The graph which shows the relationship between the precipitation time (h) and pH about Example 1. FIG. A graph showing the relationship between the precipitation time (h) and pH for Example 2. A graph showing the relationship between the precipitation time (h) and pH for Example 3.

Hereinafter, embodiments of the present invention will be described in detail.
The method for recovering the valuable metal in the present embodiment includes a separation step of separating the solution in which the valuable metal is dissolved and a precipitate containing impurities, a sinter generation step of the valuable metal, and an oxide of the valuable metal. It includes a firing step of making the metal. Examples of the valuable metal include nickel (Ni), copper (Cu), zinc (Zn) and the like contained in waste such as waste sludge from a plating factory. Examples of impurities include phosphorus (P) and tin (Sn).

Next, each of the above steps will be described in order.
(Separation process)
In the separation step, an inorganic acid (an aqueous solution of an inorganic acid) is added to a waste containing a valuable metal and stirred to form a solution in which the valuable metal is dissolved and a precipitate containing impurities containing phosphorus and tin. This is the process of separation. That is, while the valuable metal becomes a salt of an inorganic acid and exists in the solution, most of the impurities become an insoluble precipitate. Therefore, a solution of valuable metal can be obtained by filtering and removing the precipitate according to a conventional method.

As the inorganic acid, a strong inorganic acid such as sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), and hydrochloric acid (HCl) is preferably used. The concentration of the inorganic acid is preferably 1 to 2 M (molar concentration). As described above, by using a strong inorganic acid at a concentration of 1 to 2 M, a solution containing nickel sulfate (NiSO ₄ ), copper sulfate (CuSO ₄ ), zinc sulfate (ZnSO ₄ ), etc. is produced at a high concentration. be able to. That is, these nickel sulfate, copper sulfate, zinc sulfate and the like have high solubility in water. If the concentration of the inorganic acid is less than 1 M, it may not be possible to sufficiently dissolve the valuable metal in the solution. On the other hand, when the concentration of the inorganic acid exceeds 2M, the coexistence amount of the inorganic acid salts of phosphorus and tin, which are impurities, may increase in the solution.

(Oxalate production process for valuable metals)
The precious metal oxalate production step is a step of adding oxalic acid [(COOH) ₂ ] to the above-mentioned solution to form a precious metal oxalate precipitate. The ions of the valuable metal (inorganic acid salt) and oxalic acid easily react at room temperature, and the oxalate of the valuable metal precipitates as a precipitate. By filtering the precipitated precious metal oxalate precipitate according to a conventional method, the precious metal oxalate can be obtained as a precipitate with impurities remaining in the solution.

In this case, the pH of the solution is preferably 1.5 to 3.5, and in this case, the precipitation rate of the valuable metal oxalate can be increased to contribute to the improvement of the purity of the valuable metal. When this pH is less than 1.5, it takes time to precipitate the valuable metal oxalate, and the production efficiency is lowered. On the other hand, when the pH exceeds 3.5, the ion content of the valuable metal in the solution tends to decrease in the separation step.

Further, in the step of producing oxalate of a valuable metal, it is preferable to analyze the content of the valuable metal contained in the solution in advance and add 1 to 3 equivalents of oxalic acid to the valuable metal content. As described above, by analyzing the valuable metal content in the solution in advance and adding an excess of oxalic acid to the content, the valuable metal oxalate can be efficiently produced. If the amount of oxalic acid used is less than 1 equivalent with respect to the valuable metal content, the valuable metal oxalate cannot be sufficiently recovered. On the other hand, if it exceeds 3 equivalents, the amount of oxalic acid added becomes excessive, and a large amount of unreacted oxalic acid remains, resulting in waste.

As a method for analyzing the content of valuable metal contained in the solution, an inductively coupled plasma analysis method (ICP analysis method), specifically ICP-AES (ICP emission spectroscopic analysis method) or the like is adopted. Examples of the oxalate of a valuable metal include nickel oxalate [(COO) ₂ Ni], copper oxalate [(COO) ₂ Cu], zinc oxalate [(COO) ₂ Zn] and the like. The existence of the valuable metal oxalate obtained in the precious metal oxalate production step can be confirmed by analysis by an X-ray diffraction method (XRD method) or the like from a peak peculiar to the metal.

(Baking process)
An oxide of a valuable metal can be produced by calcining the oxalate of the valuable metal obtained in the oxalate production step. This calcination is carried out using, for example, an electric furnace or the like at a calcination temperature of 350 to 800 ° C. with heat generation of the valuable metal oxalate. When the calcination temperature is lower than 350 ° C., the calcination is insufficient and the conversion of the valuable metal from oxalate to an oxide tends to be insufficient. On the other hand, when the calcination temperature exceeds 800 ° C., the calcination tends to be excessive and the oxide of the valuable metal is decomposed, which is not preferable. Examples of the oxide of the valuable metal include nickel oxide (NiO, _Ni2O3 ), copper oxide ₍ Cu2O, _CuO ), zinc oxide (ZnO) and the like.

The existence of the oxide of the valuable metal after firing can be clarified by confirming the peak peculiar to the metal by the XRD method. Then, the content of the valuable metal in the calcined product can be quantified by dissolving the calcined product containing the oxide of the valuable metal in aqua regia and then analyzing by the ICP analysis method.

Next, the operation of the method for recovering the valuable metal of the present embodiment will be described.
When recovering valuable metal from waste containing valuable metal, first, an inorganic acid solution is added to the waste in the separation step to prepare a solution containing ions of the valuable metal and a precipitate containing impurities. To separate. At this time, by adjusting the concentration and the amount of the inorganic acid added, the inorganic acid salt of the valuable metal contained in the solution can be increased, and the insoluble matter of the impurities contained in the precipitate can be increased. ..

Subsequently, in the oxalate production step, oxalic acid is added to the solution to form a precipitate of valuable metal oxalate. In this case, the ions of a valuable metal such as nickel have good reactivity with oxalic acid, and the oxalate of the valuable metal is rapidly formed and becomes a precipitate. On the other hand, impurities such as phosphorus and tin have low reactivity with oxalic acid and tend to remain in the solution. Therefore, the separability between the valuable metal and the impurities can be improved.

Next, in the firing step, the valuable metal oxide can be obtained by firing the valuable metal oxalate. At this time, since the reaction of the valuable metal from the oxalate to the oxide is easy and is an exothermic reaction, the oxide of the target valuable metal can be quickly obtained by weak forced heating.

The effects obtained by the embodiments described in detail above are summarized below.
(1) In the method for recovering a valuable metal in this embodiment, a separation step of separating the valuable metal into a solution containing an inorganic acid and a precipitate containing impurities, and a separation step of adding oxalic acid to the solution to form a precipitate. It includes a step of producing a oxalate of a valuable metal to be produced and a firing step of calcining the oxalate of the valuable metal to produce an oxide of the valuable metal. Therefore, the first separation between the valuable metal and the impurities can be achieved in the separation step, and the second separation between the valuable metal and the impurities can be achieved in the oxalate production step.

Therefore, according to the method for recovering valuable metal in this embodiment, it is possible to reduce the content of impurities, improve the content of valuable metal, and recover the valuable metal by a simple method.

(2) The inorganic acid is sulfuric acid, nitric acid or hydrochloric acid. Therefore, these inorganic strong acids can easily and quickly form an inorganic acid salt of a valuable metal.
(3) The concentration of the inorganic acid is 1 to 2M. Therefore, it is possible to increase the leaching rate of valuable metals in the solution while suppressing the leaching rate of impurities.

(4) The pH of the solution of the valuable metal is 1.5 to 3.5. Therefore, it is possible to maintain the leaching rate of the valuable metal in the solution and shorten the precipitation time of the valuable metal oxalate.

(5) In the step of producing the oxalate of the valuable metal, the content of the valuable metal contained in the solution is analyzed in advance, and 1 to 3 equivalents of oxalic acid is added to the valuable metal content. In this case, the valuable metal oxalate can be sufficiently and quickly produced, and the amount of oxalic acid used can be appropriately set.

(6) In the firing step, firing is performed at 350 to 800 ° C. with heat generation of the valuable metal oxalate. Therefore, firing can be performed quickly with a small amount of forced heating, and oxides of valuable metals can be easily obtained.

(7) The valuable metal is nickel. In this case, the content of nickel oxide in the calcined product can be increased, and the formation of oxides of phosphorus and tin as impurities can be suppressed.

Hereinafter, the embodiment will be described in more detail with reference to Examples and Comparative Examples.
(Example 1)
When 10 g of nickel sludge, which is a waste of nickel, was placed in a reaction vessel, 50 mL of sulfuric acid having a molar concentration shown below was added thereto, and the mixture was stirred, a solution containing nickel sulfate and a precipitate containing impurities were found. Obtained. The precipitate was filtered according to a conventional method to obtain a solution containing nickel sulfate. The pH of this solution was measured, and the content (leaching rate) of nickel and impurities phosphorus and tin in the solution was analyzed by ICP analysis method.

The concentration of sulfuric acid is 0.5M (Example 1-1), 1.0M (Example 1-2), 1.5M (Example 1-3), 2.0M (Example 1-4), 3 It was set to 0.0M (Example 1-5), 4.0M (Example 1-6) and 5.0M (Example 1-7).

Next, oxalic acid having an amount equivalent to that of nickel in the nickel sludge was added to the solution and stirred to form a nickel oxalate precipitate. The precipitation time (h) of this precipitate was measured. Then, the precipitate was obtained by filtering by a conventional method. Subsequently, the precipitate containing nickel oxalate was fired in an electric furnace at 700 ° C. to obtain a fired product containing nickel oxide.

The obtained calcined product was dissolved in aqua regia, and the contents (% by mass) of nickel and impurities phosphorus and tin were quantified by ICP analysis method. The results are shown in Table 1.
Further, the relationship between the pH of the solution and the leaching rate (% by mass) is shown in FIG. 1, and the relationship between the pH of the solution and the precipitation time (reaction time) is shown in FIG.

表１に示したように、硫酸の濃度を１～２Ｍに設定することにより、溶解液中のニッケルの浸出率を９０質量％以上に高めることができる一方、リン及びスズの浸出率をニッケルの浸出率より十分に低く抑えることができた。また、溶解液のｐＨを１．５～３．５の範囲に設定することにより、シュウ酸ニッケルの沈殿物の析出時間を１５．５ｈ以内にすることができた。さらに、焼成物中のニッケルの含有量を７０質量％以上にできるとともに、不純物であるリン及びスズの含有量を各々０．１質量％以下に抑えることができた。

As shown in Table 1, by setting the concentration of sulfuric acid to 1 to 2 M, the leaching rate of nickel in the solution can be increased to 90% by mass or more, while the leaching rate of phosphorus and tin can be increased to that of nickel. It was possible to keep it sufficiently lower than the leaching rate. Further, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be kept within 15.5 hours. Further, the content of nickel in the fired product could be increased to 70% by mass or more, and the contents of impurities phosphorus and tin could be suppressed to 0.1% by mass or less, respectively.

Further, as shown in FIG. 1, by setting the pH of the solution in the range of 1.5 to 3.5, the leaching rate of nickel could be increased and the leaching rate of phosphorus and tin could be suppressed. Further, as shown in FIG. 4, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be shortened.

(Example 2)
When 10 g of nickel sludge was placed in the reaction vessel, 50 mL of 1 M nitric acid was added thereto, and the mixture was stirred, a solution containing nickel nitrate and a precipitate containing impurities were obtained. The precipitate was filtered according to a conventional method to obtain a solution containing nickel nitrate. The pH of this solution was measured, and the content (leaching rate) of nickel and impurities phosphorus and tin in the solution was analyzed by ICP analysis method.

The concentration of nitric acid was 0.5M (Example 2-1), 1.0M (Example 2-2), 1.5M (Example 2-3), 2.0M (Example 2-4), 3 It was set to 0.0M (Example 2-5), 4.0M (Example 2-6) and 5.0M (Example 2-7).

Next, oxalic acid having an amount equivalent to that of nickel in the nickel sludge was added to the solution and stirred to form a nickel oxalate precipitate. This precipitate was obtained by filtering by a conventional method. Subsequently, the precipitate containing nickel oxalate was fired in an electric furnace at 700 ° C. to obtain a fired product containing nickel oxide.

The obtained calcined product was dissolved in aqua regia, and the contents of nickel and impurities phosphorus and tin were quantified by ICP analysis method. The results are shown in Table 2.
Further, the relationship between the pH of the solution and the leaching rate (% by mass) is shown in FIG. 2, and the relationship between the pH of the solution and the precipitation time (h) is shown in FIG.

表２に示した結果より、硝酸の濃度を１～２Ｍに設定することにより、溶解液中のニッケルの浸出率を比較的高くすることができる一方、リン及びスズの浸出率をニッケルの浸出率より十分に低く抑えることができた。また、溶解液のｐＨを１．５～３．５の範囲に設定することにより、シュウ酸ニッケルの沈殿物の析出時間を１４ｈ以内にすることができた。さらに、焼成物中のニッケルの含有量を７０質量％以上にできるとともに、不純物であるリン及びスズの含有量を各々０．１質量％以下に抑えることができた。

From the results shown in Table 2, by setting the concentration of nitric acid to 1 to 2 M, the leaching rate of nickel in the solution can be relatively high, while the leaching rate of phosphorus and tin is the leaching rate of nickel. I was able to keep it low enough. Further, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be kept within 14 hours. Further, the content of nickel in the fired product could be increased to 70% by mass or more, and the contents of impurities phosphorus and tin could be suppressed to 0.1% by mass or less, respectively.

Further, as shown in FIG. 2, by setting the pH of the solution in the range of 1.5 to 3.5, the leaching rate of nickel could be increased and the leaching rate of phosphorus and tin could be suppressed. Further, as shown in FIG. 5, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be shortened.

(Example 3)
When 10 g of nickel sludge was placed in the reaction vessel, 50 mL of 1 M hydrochloric acid was added thereto, and the mixture was stirred, a solution containing nickel chloride and a precipitate containing impurities were obtained. The precipitate was filtered according to a conventional method to obtain a solution containing nickel chloride. The pH of this solution was measured, and the content (leaching rate) of nickel and impurities phosphorus and tin in the solution was analyzed by ICP analysis method.

The concentration of hydrochloric acid is 0.5M (Example 3-1), 1.0M (Example 3-2), 1.5M (Example 3-3), 2.0M (Example 3-4), 3 It was set to 9.0M (Example 3-5), 4.0M (Example 3-6) and 5.0M (Example 3-7).

Next, oxalic acid having an amount equivalent to that of nickel in the nickel sludge was added to the solution and stirred to form a nickel oxalate precipitate. This precipitate was obtained by filtering by a conventional method. Subsequently, the precipitate containing nickel oxalate was fired in an electric furnace at 700 ° C. to obtain a fired product containing nickel oxide.

The obtained calcined product was dissolved in aqua regia, and the contents of nickel and impurities phosphorus and tin were quantified by ICP analysis method. The results are shown in Table 3.
Further, the relationship between the pH of the solution and the leaching rate (% by mass) is shown in FIG. 3, and the relationship between the pH of the solution and the precipitation time (h) is shown in FIG.

表３に示したように、塩酸の濃度を１～２Ｍに設定することにより、溶解液中のニッケルの浸出率を比較的高くすることができる一方、リン及びスズの浸出率をニッケルの浸出率より十分に低く抑えることができた。また、溶解液のｐＨを１．５～３．５の範囲に設定することにより、シュウ酸ニッケルの沈殿物の析出時間を２０ｈ以内にすることができた。さらに、焼成物中のニッケルの含有量を６５質量％以上にできるとともに、不純物であるリン及びスズの含有量を各々０．１質量％以下に抑えることができた。

As shown in Table 3, by setting the concentration of hydrochloric acid to 1 to 2 M, the leaching rate of nickel in the solution can be relatively high, while the leaching rate of phosphorus and tin is set to the leaching rate of nickel. I was able to keep it low enough. Further, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be kept within 20 hours. Further, the content of nickel in the fired product could be increased to 65% by mass or more, and the contents of impurities phosphorus and tin could be suppressed to 0.1% by mass or less, respectively.

Further, as shown in FIG. 3, by setting the pH of the solution in the range of 1.5 to 3.5, the leaching rate of nickel could be increased and the leaching rate of phosphorus and tin could be suppressed. Further, as shown in FIG. 6, by setting the pH of the solution in the range of 1.5 to 3.5, the precipitation time of the nickel oxalate precipitate could be shortened.

(Example 4)
In Example 1, the same procedure as in Example 1 was carried out except that the amount of nickel sludge used was 133 kg and the amount of 1 M sulfuric acid used was 650 L, to obtain a calcined product of nickel oxide. The obtained calcined product was dissolved in royal water, and the content (% by mass) of nickel and impurities phosphorus and tin was quantified by ICP analysis method. As a result, nickel was 68.5% by mass and phosphorus was 0.06% by mass. And tin was 0.06% by mass.

Therefore, even if the amount of nickel sludge used was increased, the recovery rate of nickel could be increased and the content of impurities could be suppressed as in Examples 1 to 3.
(Example 5)
In the firing step of Example 1, the firing temperature of the precipitate containing nickel oxalate was changed to 300 to 900 ° C. at 100 ° C. intervals, and the firing time was changed from 30 to 120 minutes at 30 minute intervals. The nickel content (% by mass) in the calcination was quantified by the ICP analysis method. The results are shown in Table 4.

表４に示したように、焼成温度が３５０℃以上になると焼成物中のニッケルの含有量が７０質量％に近くに達し、焼成温度が８００℃までニッケルの含有量が増加することがわかる。従って、シュウ酸ニッケルを含む沈殿物の焼成温度は３５０～８００℃が好ましい。

As shown in Table 4, it can be seen that when the firing temperature is 350 ° C. or higher, the nickel content in the fired product reaches close to 70% by mass, and the nickel content increases up to the firing temperature of 800 ° C. Therefore, the firing temperature of the precipitate containing nickel oxalate is preferably 350 to 800 ° C.

(Comparative Example 1)
When 10 g of nickel sludge was placed in the reaction vessel, 50 mL of 1 M sulfuric acid was added thereto, and the mixture was stirred, a solution containing nickel sulfate and a precipitate containing impurities were obtained. The precipitate was filtered according to a conventional method to obtain a solution containing nickel sulfate. To this solution was added sodium hydroxide in approximately the same amount as the amount of nickel in the nickel sludge and stirred to form a nickel hydroxide precipitate. This precipitate was obtained by filtering by a conventional method. Subsequently, the nickel hydroxide precipitate was fired in an electric furnace at 700 ° C. to obtain a fired product containing nickel oxide.

The obtained calcined product was dissolved in royal water, and the contents of nickel and impurities phosphorus and tin were quantified by ICP analysis. As a result, nickel 63.4% by mass, phosphorus 4.3% by mass and tin 3. It was 8% by mass. From this result, the contents of phosphorus and tin, which are impurities in the fired product, showed high values far exceeding 0.1% by mass, respectively.

It is also possible to modify and embody the embodiment as follows.
-Before the separation step, a pretreatment step such as filtering and removing impurities in the waste may be provided.

-It is also possible to provide a post-treatment step such as adjusting the particle size of the fired product after the firing step.
-The waste may contain a plurality of valuable metals.

-Instead of the oxalate of the precious metal, it may be configured to generate a carbonate of the precious metal or a hydroxide of the valuable metal.

Claims (4)

A separation step in which an inorganic acid is added to a waste containing a valuable metal to form a precipitate containing a solution containing the valuable metal and an impurity containing phosphorus and tin, and the precipitate is filtered and separated.
A valuable metal oxalate production step in which oxalic acid is added to the solution to form a precious metal oxalate precipitate.
It includes a firing step of calcining the oxalate of the precious metal to produce an oxide of the valuable metal having a phosphorus and tin contents of 0.1% by mass or less, respectively .
The concentration of the inorganic acid is 1 to 2 M, and the concentration is 1 to 2 M.
The pH of the solution of the valuable metal is 1.5 to 3.5, and the pH is 1.5 to 3.5.
The valuable metal is nickel. A method for recovering a valuable metal. The method for recovering a valuable metal according to claim 1, wherein the inorganic acid is sulfuric acid, nitric acid or hydrochloric acid. Claim 1 or claim that the valuable metal content contained in the solution is analyzed in advance, and 1 to 3 equivalents of oxalic acid is added to the valuable metal content in the solution in the oxalate production step of the valuable metal. Item 2. The method for recovering valuable metals according to Item 2. The method for recovering a valuable metal according to any one of claims 1 to 3 , wherein in the firing step, firing is performed at 350 to 800 ° C. with heat generation of the valuable metal oxalate.

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