Method for recovering indium from indium-containing gypsum slag

Abstract

The invention discloses a method for recovering indium from indium-containing gypsum slag. The method comprises the following steps: 1) leaching indium-rich gypsum slag, and carrying out liquid-solid separation to obtain indium-containing leachate and leaching slag; the indium in the indium-containing leachate is directly extracted by adopting a P204 organic phase; the leaching residues are washed through waste electrolyte, so that indium-containing leaching liquid carried in the leaching residues is recycled; (2) washing the leaching residues, and carrying out liquid-solid separation to obtain indium-containing washing liquid and indium-poor gypsum residues; leaching the next batch of indium-rich gypsum slag by using the obtained indium-containing washing liquid; and (3) after indium in the indium-containing leachate is directly extracted through a P204 organic phase, a loaded organic phase and raffinate are obtained, the loaded organic phase is reversely extracted through a hydrochloric acid solution, regeneration of the loaded organic phase is achieved, an indium chloride solution is obtained, then indium chloride is replaced, sponge indium is prepared, and indium recovery is achieved. According to the method, the problems of volume expansion of an extraction system and wastewater discharge treatment are avoided, water consumption is reduced, extraction of impurity bismuth is reduced through high-acidity indium extraction, and the burden of the follow-up indium refining procedure is relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for recovering indium from indium-containing gypsum slag. Background Art

[0002] The iron alum slag and high acid leaching slag produced by hydrometallurgy are hazardous solid wastes and must be treated harmlessly according to environmental protection requirements. When smelting-reduction fuming treatment is adopted, the valuable components zinc and indium and the impurity component arsenic in the slag enter into the zinc oxide fume together, and the volatile element bismuth also enters into the zinc oxide fume.

[0003] When recovering indium from the above-mentioned complex zinc oxide dust, a sulfuric acid system is used for leaching and lime is used for neutralization and precipitation of indium to obtain indium-rich gypsum slag, and then indium is extracted from the indium-rich gypsum slag. At present, when extracting indium from indium-containing concentrates in industry, leaching and direct extraction of indium from P204 organic phase are widely used, but there are the following difficulties: 1) Indium-containing concentrates are leached to obtain indium-containing leachate, but there is inevitably a problem of indium-containing leachate being entrained in the leaching slag during liquid-solid separation. In order to reduce the entrainment loss of indium in the leaching slag, the leaching slag needs to be washed, and the addition of washing water will cause the system volume to expand; 2) When the indium-containing leachate is directly extracted to recover indium, the raffinate needs to be discharged. If the raffinate is returned to the leaching process of the indium-containing enrichment, it will inevitably cause the accumulation of soluble salts. Therefore, in actual production, the raffinate is often discharged as wastewater after the zinc is recovered by neutralization and precipitation. This leads to large water consumption in the entire system and high wastewater treatment costs. 3) For the zinc oxide smoke obtained by pyrometallurgical harmless treatment, when acid leaching, lime neutralization enrichment, indium-containing gypsum slag re-leaching, and P204 organic phase direct extraction to recover indium, the impurity bismuth will enter the organic phase system, and the subsequent indium refining process is burdened with a large burden.

[0004] Therefore, there is an urgent need in the prior art for a method for recovering indium from indium-containing gypsum slag to effectively reduce the entrainment loss of indium in the leaching slag, avoid system volume expansion and wastewater discharge treatment problems, reduce water consumption, and alleviate the burden of subsequent indium refining processes. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for recovering indium from indium-containing gypsum slag, so as to effectively reduce the entrainment loss of indium in the leaching slag, avoid the problems of system volume expansion and wastewater discharge treatment, reduce water consumption, and alleviate the burden of subsequent indium refining processes.

[0006] The object of the present invention is achieved through the following technical solution: A method for recovering indium from indium-containing gypsum slag, comprising the following steps: 1) Indium-rich gypsum slag is first leached with waste electrolyte and liquid-solid separation is performed to obtain indium-containing leachate and leach residue; indium in the indium-containing leachate is directly extracted by P204 organic phase; the leach residue is washed with waste electrolyte to recover the indium-containing leachate entrained in the leach residue; the sulfuric acid content of the waste electrolyte is 150-160 g / L; 2) After washing and liquid-solid separation of the leached residue, an indium-containing washing liquid and indium-poor gypsum residue are obtained; the next batch of indium-rich gypsum residue is leached with the obtained indium-containing washing liquid; 3) After directly extracting indium from the indium-containing leachate with P204 organic phase, a loaded organic phase and a raffinate are obtained. The loaded organic phase is back-extracted with a hydrochloric acid solution to achieve regeneration of the loaded organic phase and obtain an indium chloride solution. The indium chloride is then replaced to obtain sponge indium to achieve indium recovery.

[0007] In step 1), the indium-rich gypsum slag contains 5000-8000 g / t of indium and 0.05-0.4% of bismuth.

[0008] In step 1), when extracting indium from the indium-containing leaching solution, three-stage countercurrent extraction is adopted, and the flow ratio of the organic phase to the indium-containing leaching solution is 5.

[0009] In step 1), the P204 organic phase contains 15-20% v / v P204 extractant, and the rest is #260 solvent oil.

[0010] In step 1), the liquid-to-solid ratio of the waste electrolyte to the leached residue is 4 m 3 / t.

[0011] In step 3), the concentration of the hydrochloric acid solution is 6 mol / L.

[0012] In step 3), the raffinate has a high acid content and is returned to the leaching process of zinc oxide dust.

[0013] The beneficial effects of the present invention are as follows: the present invention effectively reduces the entrainment loss of indium in the leaching residue, avoids the volume expansion of the system and the problem of wastewater discharge treatment, reduces water consumption, extracts indium with high acidity to reduce the extraction of impurity bismuth, and reduces the burden of subsequent indium refining processes. DETAILED DESCRIPTION

[0014] The present invention is described in detail below. Example 1

[0015] A method for recovering indium from indium-containing gypsum slag comprises the following steps: 1) Indium-rich gypsum slag contains 5492 g / L indium and 0.37% bismuth. The waste electrolyte containing 158 g / L sulfuric acid is used at a liquid-to-solid ratio of 4 m 3 / t leaching, after liquid-solid separation, leaching residue and indium-containing leachate were obtained, the leachate contained 1.32 g / L indium and 0.91 g / L bismuth; P204 organic phase was used to directly extract indium from the indium-containing leachate, the P204 organic phase contained 15% v / v P204 extractant, and the rest was #260 solvent oil, the flow ratio of the organic phase to the indium-containing leachate during extraction was 5, after three-stage countercurrent extraction, the raffinate contained 3.3 mg / L indium and 0.89 g / L bismuth; 2) The leached residue is washed with a waste electrolyte having a sulfuric acid content of 158 g / L to recover the indium-containing leaching solution entrained in the leached residue, and the liquid-to-solid ratio of the waste electrolyte to the leached residue is 4 m / s. 3 / t; 3) After washing and liquid-solid separation of the leached residue, an indium-containing washing liquid and an indium-poor gypsum residue are obtained; the indium-containing washing liquid is used to leach the next batch of indium-rich gypsum residue; the indium-poor gypsum residue is disposed of as solid waste; 4) After the indium in the indium-containing leachate is directly extracted with P204 organic phase, a loaded organic phase and a raffinate are obtained. The loaded organic phase is stripped with a 6 mol / L hydrochloric acid solution to achieve regeneration of the loaded organic phase and obtain an indium chloride solution. The indium chloride is then replaced to obtain sponge indium to achieve indium recovery. The raffinate has a high acid content and is returned to the leaching process of zinc oxide dust. Example 2

[0016] A method for recovering indium from indium-containing gypsum slag comprises the following steps: 1) The indium-rich gypsum slag contains 8269 g / L indium and 0.058% bismuth. The indium-containing washing liquid in Example 1 is used at a liquid-to-solid ratio of 4 m 3 / t leaching, after liquid-solid separation, leaching residue and indium-containing leachate are obtained, the leachate contains 1.65 g / L indium and 0.523 g / L bismuth; the indium in the indium-containing leachate is directly extracted by P204 organic phase, the P204 organic phase contains 15% v / v P204 extractant, and the rest is #260 solvent oil, the flow ratio of the organic phase to the indium-containing leachate during extraction is 5, after three-stage countercurrent extraction, the raffinate contains 4.5 mg / L indium and 0.514 g / L bismuth; 2) washing the leached residue with a waste electrolyte having a sulfuric acid content of 151 g / L to recover the indium-containing leaching solution entrained in the leached residue, wherein the liquid-to-solid ratio of the waste electrolyte to the leached residue is 4 m / s. 3 / t; 3) After washing and liquid-solid separation of the leached residue, an indium-containing washing liquid and an indium-poor gypsum residue are obtained; the indium-containing washing liquid is used to leach the next batch of indium-rich gypsum residue; the indium-poor gypsum residue is disposed of as solid waste; 4) After the indium in the indium-containing leachate is directly extracted with P204 organic phase, a loaded organic phase and a raffinate are obtained. The loaded organic phase is stripped with a 6 mol / L hydrochloric acid solution to achieve regeneration of the loaded organic phase and obtain an indium chloride solution. The indium chloride is then replaced to obtain sponge indium to achieve indium recovery. The raffinate has a high acid content and is returned to the leaching process of zinc oxide dust.

[0017] In Example 1 and Example 2, for the entire leaching and extraction system for recovering indium from indium-containing gypsum slag, the solution entering the system is waste electrolyte, and the raffinate is discharged from the system. Because the content of acid-consuming substances in the indium-containing gypsum slag is low, the raffinate discharged from the system still contains 140 g / L of sulfuric acid, which can be used as a leaching agent for the leaching of zinc oxide smoke. The volumes of the waste electrolyte entering the system and the raffinate discharged from the system are equal, which effectively avoids the volume expansion problem of the system and the problem of wastewater discharge and treatment. The waste electrolyte has a high concentration of sulfuric acid, and its acidity is basically not reduced after washing the leaching slag. It has the characteristics of enhanced leaching when used to leach indium-containing gypsum slag, and efficient leaching of indium can be achieved in one stage of leaching. Since the content of acid-consuming substances in the indium-containing gypsum slag is low, the waste electrolyte is washed with leaching slag and then leached with indium-rich gypsum slag to obtain an indium-containing leaching solution with a sulfuric acid content of 140 g / L. The high-acidity indium-containing leaching solution is used as the extraction feed liquid to directly extract indium, which effectively reduces the extraction of bismuth in the indium-containing leaching solution and alleviates the burden of subsequent indium refining processes.

[0018] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for recovering indium from indium-containing gypsum slag, characterized in that The steps include: 1) Indium-rich gypsum slag is first leached with waste electrolyte and liquid-solid separation is performed to obtain indium-containing leachate and leach residue; indium in the indium-containing leachate is directly extracted by P204 organic phase; the leach residue is washed with waste electrolyte to recover the indium-containing leachate entrained in the leach residue; the sulfuric acid content of the waste electrolyte is 150-160 g / L; 2) After washing and liquid-solid separation of the leached residue, an indium-containing washing liquid and indium-poor gypsum residue are obtained; the next batch of indium-rich gypsum residue is leached with the obtained indium-containing washing liquid; 3) After directly extracting indium from the indium-containing leachate with P204 organic phase, a loaded organic phase and a raffinate are obtained. The loaded organic phase is back-extracted with a hydrochloric acid solution to achieve regeneration of the loaded organic phase and obtain an indium chloride solution. The indium chloride is then replaced to obtain sponge indium to achieve indium recovery.

2. A method for recovering indium from indium-containing gypsum slag according to claim 1, characterized in that: In step 1), the indium-rich gypsum slag contains 5000-8000 g / t of indium and 0.05-0.4% of bismuth.

3. A method for recovering indium from indium-containing gypsum slag according to claim 1, characterized in that: In step 1), when extracting indium from the indium-containing leaching solution, three-stage countercurrent extraction is adopted, and the flow ratio of the organic phase to the indium-containing leaching solution is 5.

4. A method for recovering indium from indium-containing gypsum slag according to claim 3, characterized in that: In step 1), the P204 organic phase contains 15-20% v / v P204 extractant, and the rest is #260 solvent oil.

5. A method for recovering indium from indium-containing gypsum slag according to claim 1, characterized in that: In step 1), the liquid-to-solid ratio of the waste electrolyte to the leached residue is 4 m 3 / t.

6. A method for recovering indium from indium-containing gypsum slag according to claim 1, characterized in that: In step 3), the concentration of the hydrochloric acid solution is 6 mol / L.

7. A method for recovering indium from indium-containing gypsum slag according to claim 1, characterized in that: In step 3), the raffinate has a high acid content and is returned to the leaching process of zinc oxide dust.