A process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing soot

Abstract

The present invention is a process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing ash. The arsenic- and cadmium-containing ash produced in the nonferrous metal metallurgy process is used as a raw material, and the indium, zinc, cadmium, arsenic and iron in the ash are all leached out by a hydrochloric acid solution leaching method, and then anion resin, hydrogen sulfide, calcium oxide, hydrogen peroxide and zinc sulfate are used to recover arsenic, cadmium, indium and other valuable metals respectively. The present invention does not add other inorganic salts to the system, and no industrial wastewater is generated in the whole process.

Description

Technical Field

[0001] The invention discloses a process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing smoke ash, and belongs to the technical field of hazardous waste treatment. Background Art

[0002] During the non-ferrous metal smelting process, a small amount of arsenic in the non-ferrous concentrate will be enriched in the soot of various metal smelting, such as copper soot, lead soot, bismuth soot, tin soot, antimony soot, etc. The soot contains valuable metals such as lead, zinc, copper, and indium, as well as highly toxic elements such as arsenic and cadmium, and a small amount of fluorine. These soots have both recycling value and hazardous waste. If not disposed of in time, they will have a serious impact on the ecological environment.

[0003] Chinese patent CN202310408153.9 discloses a method for recovering multiple metals in high-arsenic ash. The method adopts a process combining wet and pyrometallurgy. The ash is first acid-leached to separate the lead-tin slag, which is then smelted by pyrometallurgy to produce lead-tin alloy, and then tin and lead are separated and recovered; the acid leaching solution is neutralized, alkaline leached, and alkaline slag is acid-leached twice to separate and recover copper, separate arsenic in steps, and the secondary acid leaching solution is neutralized again. The neutralization solution recovers zinc, and the neutralization slag is alkaline-washed to further separate arsenic, and then recover indium. This method is acid-leached, alkaline-leached, and then acid-leached again. The process is long, the production cost is high, and the arsenic does not form a relatively pure product.

[0004] Chinese patent CN202210262882.3 discloses a comprehensive recovery and safe disposal method for high-arsenic materials in copper smelting, comprising the following steps: step 1, obtaining high-arsenic soot generated in copper smelting; step 2, adding alkali solution and oxygen to the high-arsenic soot for pressurized alkali leaching; step 3, filtering to obtain leached slag and leaching solution; step 4, adding excess calcium oxide to the leaching solution to generate calcium arsenate, and then drying and pelletizing in turn, reducing to obtain metallic arsenic and calcium oxide; step 5, the leaching solution is acid-leached with excess sulfuric acid, and then a mixed solution of copper sulfate and zinc sulfate and lead-bismuth slag are obtained. This method, through alkali leaching and then acid leaching, zinc and copper will also be partially leached by alkali during the alkali leaching process, and the direct recovery rate of zinc and copper is low. At the same time, this method adopts alkali high-pressure leaching + acid leaching process, and the production cost is high.

[0005] Chinese patent CN201911301824.1 discloses a method for recovering cadmium from cadmium-containing high-arsenic ash, comprising the following steps: (1) oxidative leaching: oxidative leaching of cadmium-containing high-arsenic ash, filtering to obtain a leachate containing cadmium and arsenic elements and a leachate containing valuable metals; (2) extraction: the leachate containing cadmium and arsenic elements is adjusted to pH 2.5-3.0 and then extracted to obtain a cadmium-containing organic phase and an arsenic-containing raffinate; (3) stripping: the cadmium-containing organic phase is stripped with a sulfuric acid solution to obtain a cadmium sulfate solution; (4) cadmium precipitation: the cadmium sulfate solution is subjected to a precipitation reaction with sodium sulfide to obtain cadmium sulfide; (5) arsenic solidification: a soluble ferrous salt is added to the arsenic-containing raffinate, and a gas oxidant is introduced to react to obtain scorodite crystals. The arsenic in the entire system is not recycled, and the obtained scorodite still needs to be safely disposed of. Sodium sulfide is used to precipitate cadmium, so that sodium ions enter the precipitated cadmium solution, and wastewater circulation cannot be achieved. Summary of the invention

[0006] In view of the problems existing in the existing treatment technology of arsenic- and cadmium-containing fly ash, the present invention proposes a process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing fly ash. The entire system only uses ion exchange resin, hydrogen sulfide, calcium oxide, zinc sulfate and other reagents, and no other inorganic salts are added to the system. No industrial wastewater is generated in the entire process.

[0007] The technical scheme of the present invention is: a process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing ash, wherein the indium, zinc, cadmium, arsenic and iron in the ash are all leached out by a hydrochloric acid solution leaching method to obtain a leachate and a leaching residue, and the leaching residue is sent to a lead recovery workshop; an anion resin adsorption method is adopted to adsorb arsenic in the leachate, and the resin after the arsenic adsorption is resolved to obtain an arsenic-containing solution, and a pure sodium arsenate product can be obtained by a conventional method; hydrogen sulfide in an amount of 0.36-0.46 times the mass of cadmium in the solution is introduced into the leachate after the arsenic adsorption, and the reaction is continued for a period of time, and the indium in the leachate is precipitated, and then the indium enriched slag and the indium precipitation liquid are obtained by filtering; hydrogen sulfide gas is continued to be introduced into the indium precipitation liquid, and after a certain period of reaction, the cadmium in the indium precipitation liquid is precipitated, and the cadmium enriched slag and the cadmium precipitation liquid are obtained by filtering;

[0008] The main chemical reaction equation of the process of the present invention is as follows:

[0009] As2O3+H2O =2HAsO2

[0010] As2O5+3H2O =2H3AsO4

[0011] CdO+2HCl=CdCl2+H2O

[0012] ZnO+2HCl=ZnCl2+H2O

[0013] In2O3+6HCl=2InCl3+3H2O

[0014] 2InCl3+3H2S=In2S3+6HCl

[0015] CdCl2+H2S=CdS+2HCl;

[0016] The specific process is as follows:

[0017] (1) Leaching of arsenic- and cadmium-containing ash: the leaching temperature is 80-95°C, the leaching time is 2-3 hours, the liquid-solid ratio is 3-4:1, and the amount of hydrochloric acid added is 50-60% of the mass of the arsenic- and cadmium-containing ash;

[0018] (2) Arsenic adsorption: At room temperature, the adsorption time is 1h~1.5h, anion resin is added to the leaching solution, and the amount of anion resin added is 10~15 times the mass of arsenic in the leaching solution. After the reaction is completed, the adsorption resin and the adsorbed liquid are filtered;

[0019] (3) Resin analysis: The saturated resin is analyzed using a 5% sodium hydroxide solution for 1 h to 1.5 h. After the analysis, the analysis resin and analysis solution are obtained. The analysis solution is directly used to recover sodium arsenate, and the analysis solution is returned to the arsenic adsorption process.

[0020] (4) Indium precipitation: hydrogen sulfide is introduced into the solution after arsenic adsorption. The amount of hydrogen sulfide introduced is 0.6-0.9 times the mass of indium in the solution, and the rate of hydrogen sulfide introduction is less than 0.3g / min. After the hydrogen sulfide is introduced, it can be filtered after reacting for 0.5-1h. After filtration, indium-enriched slag and indium-precipitated liquid are obtained;

[0021] (5) Cadmium precipitation: hydrogen sulfide is introduced into the solution after precipitation of indium. The amount of hydrogen sulfide introduced is 0.36-0.46 times the mass of cadmium in the solution, and the rate of hydrogen sulfide introduction is less than 0.5g / min. After the hydrogen sulfide is introduced, it can be filtered after reacting for 0.5-1h. After filtration, cadmium-enriched slag and cadmium-precipitated liquid are obtained;

[0022] (6) Oxidation to remove iron: Add calcium oxide to the solution after cadmium precipitation, adjust the pH to 3.0-3.5, and remove a small amount of fluorine in the aqueous solution while adjusting the pH. Then add hydrogen peroxide. The amount of hydrogen peroxide added is 2-3 times the mass of iron in the solution. The reaction time is 2-3 hours. After the reaction is completed, iron slag and iron-removed liquid are obtained.

[0023] (7) Sulfidation decalcification: Add zinc sulfate to the solution after oxidative deironing. The amount of zinc sulfate added is 4.02-4.05 times the mass of calcium in the solution. The reaction time is 2-3 hours. After the reaction is completed, calcium sulfate slag and zinc chloride solution are obtained.

[0024] (8) Preparation of zinc chloride: The conventional evaporation crystallization process is used to obtain zinc chloride crystals and crystallization mother liquor, and the crystallization mother liquor is returned to the arsenic and cadmium-containing ash leaching process.

[0025] Compared with the prior art, the technical effect of the present invention is as follows: since the entire system of the present invention only uses ion exchange resin, hydrogen sulfide, calcium oxide, zinc sulfate and other agents, no other inorganic salts will be added to the system, and hydrogen sulfide can precipitate all the copper, lead and bismuth heavy metal ions in the solution, so the solution after cadmium precipitation is a relatively pure zinc-iron solution, and the solution is adjusted to pH by calcium oxide, iron is removed by hydrogen peroxide, and calcium is removed by zinc sulfate to obtain a pure zinc chloride solution, and the solution is crystallized to obtain a pure zinc chloride product. No industrial wastewater is generated in the whole process.

[0026] The key technologies of the present invention are as follows:

[0027] (1) All valuable metals such as indium, zinc, cadmium, lead, and arsenic in arsenic- and cadmium-containing soot are recovered;

[0028] (2) Using hydrochloric acid solution to leach arsenic and cadmium-containing ash, the main anions in the leachate are chloride ions, arsenate ions, and arsenite ions, so that the anion resin can preferentially adsorb arsenate ions and arsenite ions, and a relatively pure arsenic-containing solution can be obtained after analysis. At the same time, arsenic can also be effectively separated from heavy metals such as zinc, cadmium, and indium;

[0029] (3) Use hydrogen sulfide to precipitate indium and cadmium step by step. Pass hydrogen sulfide into the solution after arsenic adsorption. Indium in the solution is easier to precipitate than cadmium. After indium precipitation, filter it and pass hydrogen sulfide into the solution after indium precipitation. Cadmium in the solution is easier to precipitate than zinc. No matter whether a certain amount of hydrogen sulfide is passed to precipitate indium or cadmium, the reaction is continued for 0.5-1h after the addition of hydrogen sulfide. This can make the precipitation of indium and cadmium more thorough. At the same time, a small amount of copper, bismuth and other metals in the solution can also be precipitated, which also plays a role in purifying the solution.

[0030] (4) Using a hydrochloric acid system to leach arsenic and cadmium-containing ash, using an ion exchange system to recover arsenic, using a hydrogen sulfide system to recover indium and cadmium, using calcium oxide + hydrogen peroxide to remove iron and a small amount of fluorine in the solution, and using zinc sulfate to remove calcium in the solution, so that it can be ensured that the solution after decalcification is a pure zinc chloride and hydrochloric acid solution. After evaporation and crystallization, the solution can obtain zinc chloride and pure hydrochloric acid mother liquor, which can be returned to the arsenic and cadmium-containing ash leaching process. The entire process does not discharge industrial wastewater, which can ensure that there is no wastewater discharge in production;

[0031] (5) Since the entire process system only uses cheap reagents such as hydrochloric acid, calcium oxide, and hydrogen peroxide, and the ion exchange resin can be reused, and the zinc sulfate can be recovered in the form of zinc chloride after addition, the entire system has a low production cost and good production benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a process flow chart of the present invention.

[0033] The process flow chart in the attached figure is: hydrochloric acid is used to leach all the indium, zinc, cadmium, arsenic and iron in the arsenic-containing cadmium ash to obtain a leachate and a leach residue, and the leach residue is sent to a lead recovery workshop; an anion resin is added to the leach residue leachate, and after the reaction is completed, the adsorption resin and the adsorption liquid are obtained by filtering; the saturated resin is analyzed by a 5% sodium hydroxide solution to obtain a decomposition resin and a decomposition liquid, and the decomposition liquid is directly used to recover sodium arsenate, and the decomposition liquid is returned to the arsenic adsorption process; hydrogen sulfide is introduced into the arsenic adsorption solution, and it can be filtered after the reaction, and after filtering, indium enrichment slag and indium precipitation liquid are obtained. ; Indium is recovered from indium enriched slag; hydrogen sulfide is introduced into the solution after indium precipitation, and it can be filtered after the reaction to obtain cadmium enriched slag and cadmium precipitation liquid; cadmium is recovered from cadmium enriched slag: calcium oxide is added to the solution after cadmium precipitation to adjust the pH and remove a small amount of fluorine in the solution after cadmium precipitation; hydrogen peroxide is then added, and iron slag and iron-removed liquid are obtained after the reaction is completed; zinc sulfate is added to the iron-removed liquid to remove calcium, and calcium sulfate slag and zinc chloride solution are obtained after the reaction is completed; zinc chloride solution is subjected to conventional evaporation crystallization process to obtain zinc chloride crystals and crystallization mother liquor, and the crystallization mother liquor is returned to the arsenic-containing and cadmium-containing ash leaching process. DETAILED DESCRIPTION

[0034] Example 1

[0035] (1) Take 100g of arsenic- and cadmium-containing ash, which contains 16.36% arsenic, 9.82% zinc, 0.32% iron, 17.26% lead, 0.16% bismuth, 0.52% indium, and 6.83% cadmium. Add 47mL of hydrochloric acid and 300mL of water to the ash. Leach for 2.5h at 85℃. After leaching, filter to obtain 62.32g of leaching residue and 328mL of leaching solution. The leaching solution contains 49.37g / L arsenic, 1.56g / L indium, 20.61g / L cadmium, 29.63g / L zinc, 0.92g / L iron, and 0.25g / L fluorine.

[0036] (2) Arsenic adsorption: 165 g of anion resin was added to the leaching solution. At room temperature, the adsorption time was controlled to be 1 h. After the reaction was completed, 205.12 g of adsorption resin and 310 mL of adsorbed liquid were obtained by filtration.

[0037] (3) Resin analysis: The saturated resin was analyzed using a 5% sodium hydroxide solution for 1 h. After the analysis, 170.13 g of analysis resin and analysis solution were obtained. After pretreatment and crystallization of the analysis solution, 90.62 g of hydrated sodium arsenate was obtained, which contained 17.60% arsenic.

[0038] (4) Indium precipitation: 0.41 g of hydrogen sulfide was introduced into the solution after arsenic adsorption at a rate of 0.1 g / min. After the hydrogen sulfide was introduced, the solution was reacted for 40 min and then filtered immediately. After filtration, 1.56 g of indium precipitated solution and indium-enriched slag containing 32.36% indium were obtained;

[0039] (5) Cadmium precipitation: 2.7 g of hydrogen sulfide was introduced into the indium precipitation solution at a rate of 0.2 g / min. After the introduction of hydrogen sulfide was completed, the solution was allowed to react for 40 min and then filtered immediately. After filtration, 13.31 g of cadmium precipitation solution and cadmium-enriched slag were obtained, which contained 50.26% cadmium.

[0040] (6) Oxidation for iron removal: Add calcium oxide to the solution after cadmium precipitation, adjust the pH to 3.0-3.5, then add 0.7g of hydrogen peroxide, react for 2h and filter to obtain iron slag and iron removal solution;

[0041] (7) Sulfidation decalcification: Add zinc sulfate (23.46 g) to the solution after oxidative deironing. After a reaction time of 2 h, calcium sulfide slag and zinc chloride solution are obtained.

[0042] (8) Preparation of zinc chloride: The conventional evaporation crystallization process is used to obtain zinc chloride crystals and crystallization mother liquor, and the crystallization mother liquor is returned to the arsenic and cadmium-containing ash leaching process.

[0043] Example 2

[0044] (1) Take 1000g of arsenic- and cadmium-containing fly ash, which contains 12.23% arsenic, 12.16% zinc, 0.26% iron, 13.82% lead, 0.39% indium, and 8.12% cadmium. Add 492mL of hydrochloric acid and 3000mL of water to the fly ash. Leach at 90°C for 3h. After leaching, filter to obtain 582.35g of leached residue and 3316mL of leachate. The leachate contains 36.51g / L arsenic, 1.16g / L indium, 24.24g / L cadmium, 36.30g / L zinc, 0.76g / L iron, and 0.18g / L fluorine.

[0045] (2) Arsenic adsorption: 1455 g of anion resin was added to the leaching solution. Under normal temperature, the adsorption time was controlled to be 1.5 h. After the reaction was completed, 1633.52 g of adsorption resin and 3222 mL of adsorbed liquid were obtained by filtration.

[0046] (3) Resin analysis: The saturated resin was analyzed using a 5% sodium hydroxide solution for 1.5 h. After the analysis, 1566 g of analysis resin and analysis solution were obtained. After pretreatment and crystallization of the analysis solution, 688.66 g of hydrated sodium arsenate was obtained, which contained 17.58% arsenic.

[0047] (4) Indium precipitation: 2.7 g of hydrogen sulfide was introduced into the solution after arsenic adsorption at a rate of 0.2 g / min. After the hydrogen sulfide was introduced, the solution was reacted for 50 min and then filtered immediately. After filtration, 12.05 g of indium precipitated solution and indium-enriched slag containing 31.58% indium were obtained.

[0048] (5) Cadmium precipitation: 32.15 g of hydrogen sulfide was introduced into the indium precipitation solution at a rate of 0.4 g / min. After the introduction of hydrogen sulfide was completed, the solution was allowed to react for 50 min and then filtered immediately. After filtration, 151.34 g of cadmium precipitation solution and cadmium-enriched slag containing 52.58% cadmium were obtained.

[0049] (6) Oxidation for iron removal: Add calcium oxide to the solution after cadmium precipitation, adjust the pH to 3.0-3.5, then add 6.3g of hydrogen peroxide, react for 2h and filter to obtain iron slag and iron removal solution;

[0050] (7) Sulfuric acid decalcification: Add zinc sulfate (191.87 g) to the solution after iron removal by oxidation. After a reaction time of 3 h, calcium sulfate slag and zinc chloride solution are obtained.

[0051] (8) Preparation of zinc chloride: The conventional evaporation crystallization process is used to obtain zinc chloride crystals and crystallization mother liquor, and the crystallization mother liquor is returned to the arsenic and cadmium-containing ash leaching process.

Claims

1. A process for recovering arsenic, cadmium, indium and other valuable metals from arsenic- and cadmium-containing ash, using hydrochloric acid solution leaching to leach all indium, zinc, cadmium, arsenic and iron in the ash to obtain leaching solution and leaching residue, which is sent to a lead recovery workshop; the process is characterized by: Anion resin is added to the leaching solution, and after the reaction, the adsorption resin and the adsorption liquid are obtained by filtering; the saturated resin is analyzed by using a 5% sodium hydroxide solution to obtain a analytical resin and an analytical liquid, and the analytical liquid is returned to the arsenic adsorption process for direct use in recovering sodium arsenate; hydrogen sulfide is introduced into the arsenic adsorption solution, and the solution can be filtered after the reaction to obtain indium enriched slag and indium precipitation liquid; indium is recovered from the indium enriched slag; hydrogen sulfide is introduced into the indium precipitation solution again, and the solution can be filtered after the reaction to obtain cadmium enriched slag and cadmium precipitation liquid; cadmium is recovered from the cadmium enriched slag: calcium oxide is added to the cadmium precipitation solution to adjust the pH while removing a small amount of fluorine in the cadmium precipitation liquid; then hydrogen peroxide is added, and iron slag and iron removal liquid are obtained after the reaction; zinc sulfate is added to the iron removal liquid to remove calcium, and calcium sulfate slag and zinc chloride solution are obtained after the reaction; zinc chloride solution is subjected to a conventional evaporation crystallization process to obtain zinc chloride crystals and crystal mother liquor, and the crystal mother liquor is returned to the arsenic-containing cadmium ash leaching process; The specific process is as follows: (1) Leaching of arsenic- and cadmium-containing ash: the leaching temperature is 80-95°C, the leaching time is 2-3h, the liquid-to-solid volume mass ratio is 3-4:1 mL / g, and the amount of hydrochloric acid added is 50-60% of the mass of the arsenic- and cadmium-containing ash; (2) Arsenic adsorption: At room temperature, the adsorption time is 1-1.5 h. Anion resin is added to the leaching solution. The amount of anion resin added is 10-15 times the mass of arsenic in the leaching solution. After the reaction is completed, the adsorption resin and the adsorbed liquid are filtered out; (3) Resin decomposition: The saturated resin is decomposed using a 5% sodium hydroxide solution for 1-1.5 h. After the decomposition is completed, decomposition resin and decomposition liquid are obtained. The decomposition liquid is returned to the arsenic adsorption process and directly used to recover sodium arsenate. (4) Indium precipitation: hydrogen sulfide is introduced into the solution after arsenic adsorption. The amount of hydrogen sulfide introduced is 0.6-0.9 times the mass of indium in the solution. The rate of hydrogen sulfide introduction is less than 0.3 g / min. After the hydrogen sulfide is introduced, it reacts for 0.5-1 h and then can be filtered. After filtration, indium-enriched slag and indium precipitation liquid are obtained; (5) Cadmium precipitation: hydrogen sulfide is introduced into the solution after indium precipitation. The amount of hydrogen sulfide introduced is 0.36-0.46 times the mass of cadmium in the solution. The rate of hydrogen sulfide introduction is less than 0.5 g / min. After the hydrogen sulfide is introduced, the solution is allowed to react for 0.5-1h before filtering. After filtering, cadmium-enriched slag and cadmium-precipitated solution are obtained. (6) Oxidation to remove iron: Add calcium oxide to the solution after cadmium precipitation, adjust the pH to 3.0-3.5, and remove a small amount of fluorine in the aqueous solution while adjusting the pH. Then add hydrogen peroxide. The amount of hydrogen peroxide added is 2-3 times the mass of iron in the solution. The reaction time is 2-3 hours. After the reaction is completed, iron slag and iron-removed liquid are obtained. (7) Sulfidation decalcification: Add zinc sulfate to the solution after oxidative deironing. The amount of zinc sulfate added is 4.02-4.05 times the mass of calcium in the solution. The reaction time is 2-3 h. After the reaction is completed, calcium sulfate slag and zinc chloride solution are obtained. (8) Preparation of zinc chloride: The conventional evaporation crystallization process is used to obtain zinc chloride crystals and crystallization mother liquor, and the crystallization mother liquor is returned to the arsenic and cadmium-containing ash leaching process.

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