JPH0477053B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for removing fluorine as an impurity from a valuable metal leachate. [Prior art] In general, in hydrometallurgical zinc smelting, zinc sulfide contained in ore is roasted to produce zinc oxide, which is leached with sulfuric acid and/or a sulfuric acid acidic electrolytic waste solution, and then Cu, Cd, and Ni in the leaching solution are , Co, and other impurities are removed using an appropriate method to prepare a highly pure zinc sulfate solution. This solution is electrolyzed to strip off the zinc deposited on the cathode, melted in an electric furnace, and then cast. In order to collect high-purity zinc with stable operation, when electrolyzing zinc sulfate solution,
It is important to remove impurities that may cause trouble from this liquid in advance. It is well known that various impurities cause various problems during the electrowinning of zinc, but among them, fluorine corrodes the aluminum cathode plate and removes zinc precipitates from the cathode. It has been found that adhesion to the plate surface makes it extremely difficult to strip the deposited zinc from the cathode plate. The problem caused by this fluorine is particularly serious when wet-processing so-called oxide ores such as zinc silicate ores. This is because, in the case of zinc sulfide ore, most of the fluorine is volatilized by roasting;
In the case of oxidized ores, the fluorine does not volatilize by roasting, which is usually carried out. In our tests, we were able to reduce zinc sulfide concentrate containing 100 to 200 ppm of fluorine to 10 ppm or less by roasting it; ₃ ) Even if oxide ores made of minerals such as hemimorphite (H ₂ Zn ₂ SiO ₅ ) are roasted at approximately 800°C, fluorine does not volatilize, but rather the carbonate roots of zinc carbonate ores decompose. The fluorine content increased to 250ppm due to the volatilization. Based on this experience, in order to remove fluorine from such oxidized ores by dry processing, it is possible to add a sulfur source, such as sulfide ores, to the oxidized ores, mix them, and then roast them. Although it is possible to apply this method to the process described above, firstly, the equipment cost increases, and secondly, it requires measures against environmental pollution, so it cannot be said that it is an economically advantageous method. As a means of removing fluoride ions from acidic liquid,
Since the solubility of calcium fluoride is extremely low, it may be possible to neutralize it by adding calcium salts such as quicklime, slaked lime, or calcium carbonate to form a precipitate, and then separate the precipitate. The inventors tested an acidic aqueous solution of zinc sulfate and found that fluorine could not be removed sufficiently. That is, the present inventors added fluorine to 200mg/
Calcium salts such as calcium carbonate were added to the sulfuric acid solution containing zinc sulfate until the pH reached 5, but the fluorine concentration in the solution from which the generated precipitate was separated was about 90 mg/day, and The concentration was approximately 500 mg/, which was much higher than the fluorine concentration of 8.7 mg/, which was calculated from the solubility product of CaF ₂ . This is because although free sulfuric acid was fixed to the plaster by calcium, the sulfate ions of zinc sulfate present in the solution interfered with the fixation of fluoride ions to calcium fluoride, resulting in the removal of fluoride. It is considered that this was insufficient. This is a fatal obstacle to the removal of fluorine in zinc hydrometallurgy, which processes ore by dissolving it in sulfuric acid, and generally it is considered difficult to remove fluorine from leachate. Currently, as a countermeasure against fluorine, the surface of the cathode is treated by some method. [Object of the Invention] The present invention was made to solve the above-mentioned problems caused by conventional fluorine. The purpose is to advantageously obtain valuable metals from high fluorine-containing raw materials. [Structure of the Invention] The present invention provides a solution for dissolving and leaching zinc-containing raw materials such as ores, scraps, and slags with sulfuric acid and/or electrolytic tailings, or at a time before or after the dissolving and leaching of zinc-containing raw materials such as ores, scraps, and slags. Ion concentration is 0.1g/
Iron scrap or a salt containing divalent iron such as ferrous sulfate is added so that the concentration of trivalent aluminum ions in the solution is ~10 g/, preferably 0.5 g/~2 g/. 10mg/~2000mg/
, desirably 100 mg/~1000 mg/aluminum scrap or an acid-soluble salt such as aluminum sulfate. Next, quicklime and calcium carbonate are added to the leached liquid as a neutralizing agent.
Add slaked lime, zinc oxide, zinc ore, or a combination of some, and adjust the pH to 2-6.
Preferably, the number is adjusted to 4 to 6. Also,
In order to oxidize the divalent iron ions in the leachate to trivalent from just before neutralization until the completion of neutralization,
Add an oxidizing agent such as potassium permanganate or manganese dioxide or electrolytically crusted manganese. The neutralized solution is purified using commonly used methods such as zinc powder, arsenous acid method, antimony method, and α-nitroso-β-naphthol method, and then undergoes an electrolysis process to finally achieve high purity. of zinc is deposited. Furthermore, in order to achieve the purpose of removing fluorine from a solution containing valuable metals, the present invention provides a solution without adding acid-soluble salts such as aluminum scraps or aluminum sulfate during the process of dissolving ores, etc. In the process of neutralizing aluminum with calcium carbonate, etc., ordinary aluminum oxide powder or activated alumina powder is used.
By adding 0.1 g or more, the same effect as the above method can be obtained. In the present invention, if the amount of iron source added is such that the iron concentration in the leachate is 0.1 g/or more, the effect of removing fluoride is recognized, but if the amount is 10 g/or more, the extraction rate of zinc decreases. Also, hypersensitivity decreases. In the range of 0.5g/~2g/, not only can the fluorine concentration in the leachate, which is 60mg/or more, be neutralized to reduce the fluorine concentration to 20mg/or less, but also the zinc extraction rate and hypersensitivity can be reduced. can be higher than if no iron was included. Further, the effect of removing fluorine is observed when the amount of aluminum added is such that the aluminum concentration in the leachate is 10 mg/or more, and the effect of removing fluorine increases as the amount of aluminum added increases. However, if the amount is 2000 mg/or more, the permeability of the leaching slurry decreases, making it unsuitable for industrial applications. If the aluminum concentration in the leachate is 100mg/~1000mg/, even if the fluorine concentration in the leachate is as high as 60mg/ or more,
The concentration of the neutralizing solution can be reduced to 20mg/or less,
Moreover, it is possible to maintain a high extraction rate and hypersensitivity of zinc. Alternatively, instead of adding acid-soluble aluminum or its salt during the dissolution process, aluminum oxide can be added during the neutralization process to reduce the concentration of fluorine in the neutralization solution to 20mg/or less. Moreover, in this case, in principle, no gel formation of aluminum hydroxide is involved, so even if the amount of aluminum is 2000 mg/or more, the hyperactivity will not be impaired. Although the mechanism of fluorine removal in the method of the present invention has not yet been completely elucidated in terms of reaction mechanism, it is thought to involve a coprecipitation reaction with iron and aluminum or an adsorption reaction of these to hydroxide precipitates. In other words, divalent iron ions dissolved in the leachate are oxidized by potassium permanganate, etc., and in the process of neutralizing the leachate, fluoride ions precipitate as hydroxides along with aluminum. If the concentration is as high as 100 mg/min or more, it may partially precipitate as calcium fluoride due to neutralization, but if the concentration is not that high, it remains as an ion and precipitates as a complex of iron and aluminum hydroxide. It is thought that it is taken up by things such as adsorption and precipitates. [Examples of the Invention] Examples of the present invention will be described below along with comparative examples. Example 1 125 g of zinc silicate ore was dissolved using electrolytic tailings. During the dissolution, 5.5 g of ferrous sulfate and 3.5 g of aluminum sulfate were added. The amount of these additions is
Each amount corresponded to 1 g of Fe ²⁺ / 500 mg of A ³⁺ . After the leaching was completed, the pH of the leaching slurry was 1.5 and 1.2. After leaching, 1.6 g of KMnO ₄ was added to the slurry, and then a slurry of calcium carbonate dissolved in water was added to adjust the pH to 5.0. A commercially available flocculating agent was added to the neutralized slurry to flocculate the precipitate, which was then filtered. In addition to analyzing F in the solution in which the ore was dissolved and the solution filtered after neutralization to investigate the F removal rate, the results of measuring the Zn extraction rate, residue generation rate, and overrate were reported in the first study.
Shown in the table.

[Table] Comparative Example 1 Zinc silicate was dissolved in the same manner as shown in Example 1, and the amount of additive was changed to Fe ²⁺ of 0, 1, 2,
4 g/KMnO ₄ was used in an amount necessary to oxidize each Fe ²⁺ to Fe ³⁺ , and A ³⁺ was not added. The results are shown in Table 2 below.

[Table] As is clear from Table 2, as the amount of Fe ²⁺ added increases, the effect of F removal increases, but the Zn extraction rate and overrate peak at 1 g/ ^{Fe 2+} It decreased as the amount of addition increased. Example 2 400g of zinc silicate ore was continuously dissolved and leached,
At the same time, ferrous sulfate, ferrous sulfate, and aluminum sulfate were added, each with a Fe ²⁺ concentration of 1 g/A.
It was added so that the ³⁺ concentration was 500 mg/d, and completely dissolved. A slurry of calcium carbonate dissolved in water is added to the slurry after leaching, and the pH is adjusted.
It was set at 4.5 to 5.0. Potassium permanganate was added during neutralization, and a final chemical analysis was performed to ensure complete oxidation of Fe ²⁺ in the solution. Thereafter, a commercially available flocking agent was added to flocculate the precipitate.
The neutralized slurry was filtered, and zinc powder and arsenous acid were added to about 2800 ml of the solution to clean it. The cleaning solution was electrolyzed under the following conditions.

[Table] After the electrolysis was completed, the electrolytic tailings was used repeatedly to dissolve the ore, and this series of continuous steps was repeated four times. Figure 1 shows the results of analyzing the F concentrations of the leachate and the neutralized liquid during this continuous repeated test. As is clear from FIG. 1, the F concentration decreased by 20 to 30 mg/during the neutralization process, and as the number of repetitions increased, the F concentration in the neutralized solution equilibrated to 18 mg/dc.
The results of the leaching test after the fourth repetition are as follows.

[Table] Comparative Example 2 In the same method as in Example 3, ferrous sulfate was added in the amount of additive, and Fe ²⁺ concentration in the leachate was 1.
The amount of potassium permanganate required to oxidize all of the Fe ²⁺ in the solution to Fe ³⁺ was adjusted to be 1 g/g/, and no A source was added. The process was repeated six times and the F concentration of the exudate and after neutralization was measured. The results are shown in Figure 2. As is clear from Figure 2, just adding Fe reduces F by about 10 mg/kg, but as the process is repeated, the F concentration in the leachate and the neutralized solution gradually increases, and in the neutralized solution, the F concentration gradually increases. It was equilibrated to about 40mg/. That is, although it is possible to remove some F by co-precipitation with Fe, it has not been possible to reduce the F concentration to 20 mg/or less, which is required for zinc electrosmelting. Comparing the results of Example 2 and Comparative Example 2, Fe
It is recognized that the effect of the present invention of simultaneously precipitating A and A is remarkable. The results of the leaching test after the sixth repetition are as follows.

[Table] Example 3 Zinc silicate was dissolved in the same manner as in Example 1, and the amount of additive in the leachate was determined.
The concentration of Fe ²⁺ is 1 g/, the concentration of A ³⁺ is 0.10,
Ferrous sulfate and aluminum sulfate were added at the time of dissolution in amounts of 100, 500, 1000, and 2000 mg, respectively, and the amount necessary to oxidize all Fe ²⁺ in the leachate to Fe ³⁺ was added. Potassium permanganate was added to the leachate during neutralization and filtered after neutralization was completed. The results obtained regarding overrate and F concentration of the neutralized solution are shown in FIG. As is clear from FIG. 3, as the A ³⁺ concentration in the leachate was increased, the F concentration in the neutralized liquid decreased rapidly. On the other hand, the overrate does not change much when the A ³⁺ concentration is up to 500 mg/, but it decreases rapidly when the A 3+ concentration exceeds 500 mg/.
The amount was 0.6 ml/cm ² mm, about 1/3 of that in the case of . Example 4 125 g of silicozinc ore was dissolved in electrolytic tailings, and 5.5 g of ferrous sulfate was added thereto. Leaching chiller amount 1.2
, PH was set to 1.8. _KMnO4 to leaching slurry
1.6g was added, and calcium carbonate slurry was further added to neutralize it to a pH of 4.9. Immediately after neutralization, add 0.5% of 99% pure alumina powder.
g was added and stirring was continued for 1 hour. A commercially available flocking agent was then added to flocculate the precipitate and filtered.
Table 5 shows the results of analyzing the solution in which the ore was dissolved and the F of the solution to measure the F removal rate, Zn extraction rate, residue production rate, and overrate.

〔Effect of the invention〕

The present invention is an extremely simple process in which, as described above, in the process of dissolving ore and neutralizing the solution, appropriately determined amounts of an iron source, an aluminum source, and an oxidizing agent for oxidizing divalent iron are added. This method makes it possible to always keep the fluorine concentration in the electrolyte below 20 mg even when ores with high fluorine content are wet-processed. Furthermore, this method improves the extraction rate of zinc and improves the superconcentration of the leaching slurry. This method is extremely useful as a method for removing fluorine when mass producing high-purity zinc by hydrometallurgical smelting.

[Brief explanation of drawings]

Figure 1 shows the case where Fe and A are added. Figure 2 shows the case where Fe and A are added.
Figure 3 is a graph showing the relationship between the number of repetitions and the F concentration of the leachate and the neutralized liquid in each continuous repeated test when only Fe is added.
It is a graph showing the relationship between the F concentration of the neutralized solution and the overspeed when the amount of F added is changed.

Claims (1)

[Scope of Claims] 1. When extracting valuable metals by dissolving raw materials such as ores, scraps, or slags containing valuable metals in an acidic mineral acid solution such as sulfuric acid, and extracting valuable metals, During or before and after dissolution, iron scrap or salt containing divalent iron is added so that the Fe ²⁺ concentration in the solution is 0.1 g/~10 g/.
In addition, aluminum scrap or acid-soluble aluminum salt is added to the solution with an A ³⁺ concentration of 10 mg/~
2000mg/, then add the necessary amount of oxidizing agent to oxidize all or part of the Fe ²⁺ in the solution to Fe ³⁺ , add a neutralizing agent, and adjust the pH of the solution. 2 to 6, and a method for removing fluorine in wet processing of valuable metals, characterized by precipitating iron and aluminum hydroxides and co-precipitating fluorine at the same time. 2. The iron scraps or salts containing divalent iron are dissolved in a solution with an Fe ²⁺ concentration in the range of 0.5 g/~2 g/, and the aluminum scraps or acid-soluble aluminum salts are mixed with A in the solution solution. ³⁺ concentration is 100mg/
2. The method for removing fluorite in wet processing of valuable metals according to claim 1, wherein the amount is added in the range of ~1000 mg/. 3. The method for removing fluorine in wet processing of valuable metals according to claim 1, characterized in that a neutralizing agent is added to neutralize the solution so that the pH thereof is in the range of 4 to 6. 4 When raw materials such as ores containing valuable metals or scraps or slags are dissolved in an aqueous solution of mineral acids such as sulfuric acid, and valuable metals are leached out and valuable metals are collected, the raw material ores, etc., are dissolved during or before or after the melting. In the process, iron scrap or a salt containing divalent iron is added so that the Fe ²⁺ concentration in the solution is 0.1 g/~10 g/, and then all or part of the divalent iron in the solution is added to the divalent iron. Add the necessary amount of oxidizing agent to oxidize iron, then add a neutralizing agent to adjust the pH of the solution to 2 to 6.
A method for removing fluorine in wet processing of valuable metals, the method comprising: further adding 0.1 g/or more of aluminum oxide to co-precipitate fluorine together with iron hydroxide and aluminum oxide precipitates. 5. The wet method for valuable metals according to claim 4, characterized in that the iron scrap or the salt containing divalent iron is added at a concentration of Fe ²⁺ in the solution in the range of 0.5 g/ to 2 g/. Fluoride removal method in processing. 6. The method for removing fluorine in wet processing of valuable metals according to claim 4, which comprises adding a neutralizing agent to neutralize the solution so that the pH thereof falls within the range of 4 to 6.