A comprehensive treatment method for arsenic-containing soot

Abstract

The application discloses a comprehensive treatment method of arsenic-containing fly ash, which comprises the following steps: (1) mixing the arsenic-containing fly ash and a dearsenization agent, and then performing low-temperature roasting to obtain high-arsenic fly dust and roasting slag; the dearsenization agent comprises a persulfate salt, and the mass ratio of the arsenic-containing fly ash to the persulfate salt is 1:(0.4-1); (2) performing sulfuric acid leaching on the roasting slag to obtain an indium-containing leaching solution and a leaching residue. In the application, the persulfate salt is used as the dearsenization agent, and the dearsenization agent slowly releases H2SO4 and SO2 in the low-temperature roasting process; the H2SO4 and SO2 react with arsenic compounds in the fly ash to generate volatile As2O3, so that the dearsenization effect is achieved; the problems, such as serious environmental pollution caused by acid mist and corrosion of equipment in the low-temperature roasting dearsenization process using concentrated sulfuric acid in the traditional process, are solved, and the whole process of the application is more clean and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling, and in particular relates to a comprehensive treatment method for arsenic-containing flue dust. Background Technology

[0002] Zinc oxide leaching residue contains valuable metals such as lead. Reduction smelting is commonly used to recover these metals. However, this process often produces high-arsenic fumes. These fumes contain not only arsenic but also various volatile valuable metals such as indium, cadmium, antimony, and zinc. Their main components are: As 10–50%, In 0.4–5%, Pb 10–20%, Zn 5–10%, Cd 5–15%, Sb 5–10%, Sn 1–5%, and moisture 0.1–25%. Due to their high arsenic content and complex composition, the arsenic is dispersed during valuable metal recovery, making centralized recovery or harmless treatment difficult, posing a significant environmental risk. Currently, the treatment of arsenic-containing fumes primarily uses wet methods, supplemented by pyrometallurgical methods.

[0003] The wet process for treating arsenic-containing flue dust primarily involves arsenic removal followed by the recovery of valuable metals, mainly using alkaline methods and supplemented by acid methods. Patent application number 201410189851.5 discloses a multi-metal integrated recovery process for arsenic-containing flue dust. This patent uses selective leaching to obtain a zinc- and copper-containing leachate and an arsenic- and lead-containing leaching residue. The leachate is extracted separately with copper and zinc extractants, then back-extracted and electrowinning to obtain copper and zinc. The leaching residue is leached with a mixed arsenic removal agent of H₂O₂ and Na₂S₂O₃ to obtain an arsenic-containing leachate and a lead-containing arsenic-removed leaching residue. The arsenic-containing leachate is concentrated and crystallized to obtain sodium arsenate. The arsenic-removed leaching residue is then subjected to pyrometallurgical lead extraction and electrolytic refining to obtain lead, effectively recovering metallic copper, zinc, and lead, thus achieving resource utilization of arsenic. The main problems with this method are the long processing flow and the fact that the obtained sodium arsenate is still hazardous waste requiring further treatment. Patent application number 201610998354.9 discloses a method for removing arsenic from arsenic-containing fly ash by employing a first-stage hydrothermal leaching and a second-stage alkaline leaching, with the leaching solutions from both stages cooled and crystallized to obtain arsenic-containing crystals. However, the sodium arsenate obtained by this method still requires further processing, and the resulting crystallization mother liquor has a high arsenic content, leading to high-concentration wastewater that also requires further treatment. Patent application number 201711055834.2 discloses a low-cost method for removing arsenic from copper smelting high-arsenic fly ash by preparing calcium arsenate through atmospheric pressure alkaline leaching and lime causticization of the alkaline leaching solution. However, the calcium arsenate slag obtained by this method has a low arsenic content, resulting in a large slag volume and high landfill costs. Patent application number 201710145148.8 discloses a method for removing arsenic by electrochemical dissolution after mixing alkali, solvent, and arsenic-containing fly ash. This method generates hydrogen arsine in the solution during the electrochemical arsenic removal process, posing certain safety hazards. Furthermore, the resulting arsenic-containing solution requires further processing and does not achieve the resource utilization of arsenic. Alkaline arsenic removal processes are widely used because other valuable metals are difficult to leach out during the arsenic removal process. The main products are sodium arsenate and calcium arsenate. However, the main drawbacks of the alkaline process are high alkali costs, low arsenic content in the resulting sodium arsenate and calcium arsenate, leading to large amounts of slag. Furthermore, sodium arsenate and calcium arsenate require further landfill treatment, and the final arsenic-containing tailings also need treatment. Therefore, the alkaline process generally suffers from long processing times and high costs. Acidic processes are also used for arsenic removal. For example, patent application number 201410690393.3 discloses a method of leaching arsenic-containing flue dust with waste acid, followed by arsenic slag removal via cyclone electrowinning. This process not only purifies the waste acid but also completely eliminates gypsum slag, achieving the goal of treating arsenic-containing flue dust. The main safety risk of this method is the potential for the generation of arsine during electrowinning, which could endanger human safety. Patent application number 201910594277.4 discloses a method of acid leaching arsenic-containing flue dust, followed by stepwise reduction of the resulting arsenic-containing acid solution with iron powder to obtain elemental arsenic. The reduction process utilizes Cu... 2+Using an activator, the resulting filter residue is magnetically separated after the reaction to obtain high-purity elemental arsenic, thus reducing the volume of arsenic-containing flue dust. However, this method generates arsine during the displacement process, posing a safety hazard. In the acid process for arsenic removal, other valuable metals are also leached along with the arsenic, increasing the difficulty of arsenic separation. Furthermore, the removal of arsenic in acidic solutions easily generates arsine, posing serious safety risks.

[0004] Clearly, wet processes, whether alkaline or acidic, generally suffer from long process flows, requiring further treatment or landfilling of the arsenic-containing products, and the difficulty in treating arsenic-containing wastewater.

[0005] Since arsenic-containing flue dust is mainly produced by pyrometallurgical systems, arsenic removal using pyrometallurgical processes is difficult, and there are currently few publicly disclosed patents for pyrometallurgical treatment of arsenic-containing flue dust. For example, patent application number 201410839413.9 discloses a method for removing arsenic by mixing concentrated sulfuric acid with pulverized coal and arsenic-containing flue dust, followed by leaching the arsenic-removed roasted ash into an indium recovery system to recover zinc and indium. This process has a significant arsenic removal effect and further sulfitizes other metals into soluble sulfates, which has certain advantages. However, due to the use of concentrated sulfuric acid, which easily leads to a poor batching environment and severe equipment corrosion, this technology has not been widely adopted.

[0006] Therefore, for the comprehensive recycling and treatment of high-arsenic flue dust, there is an urgent need to develop cleaner, more efficient, and shorter-process arsenic removal technologies to achieve effective separation of arsenic and comprehensive recycling and utilization of other valuable metals in arsenic-containing flue dust. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and to provide a comprehensive treatment method for arsenic-containing flue dust.

[0008] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0009] A comprehensive treatment method for arsenic-containing flue dust includes the following steps:

[0010] (1) Arsenic-containing flue dust and arsenic removal agent are mixed and then calcined at low temperature to obtain high-arsenic flue dust and calcination residue; the arsenic removal agent includes persulfate, and the mass ratio of arsenic-containing flue dust to persulfate is 1:(0.4~1);

[0011] (2) The roasted residue is leached with sulfuric acid to obtain an indium-containing leachate and a leaching residue.

[0012] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, in step (1), the arsenic removal agent further includes bisulfate; the mass ratio of the arsenic-containing flue dust to persulfate and bisulfate is 1:(0.4~1):(0.1~0.5).

[0013] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, in step (1), the persulfate is one or more of ammonium persulfate, sodium persulfate, and potassium persulfate;

[0014] The bisulfate is one or more of sodium bisulfate and potassium bisulfate.

[0015] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, in step (1), the low-temperature roasting temperature is 300-500℃, the roasting time is 2-4h, and the roasting is carried out in an air atmosphere.

[0016] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, in step (1), the volatilization rate of arsenic by low-temperature roasting is greater than 95%, and the loss rate of indium is less than 5%.

[0017] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, in step (1), the main components of the arsenic-containing flue dust to be treated, by mass percentage, include: As 10-50%, In 0.4-5%, Pb 10-20%, Zn 5-10%, Cd 5-15%, Sb 5-10%, Sn 1-5%, and moisture 0.1-25%.

[0018] The preferred method for the comprehensive treatment of arsenic-containing flue dust is to mix the high-arsenic flue dust obtained in step (1) with iron slag and then perform reduction smelting to prepare arsenic-iron alloy.

[0019] In the above-mentioned comprehensive treatment method for arsenic-containing soot, preferably, in step (2), during the sulfuric acid leaching process, the liquid-solid mass ratio is 3:5 to 1, the leaching temperature is 60 to 80°C, the leaching time is 1 to 3 hours, and the sulfuric acid concentration in the solution is 100 to 150 g / L when the sulfuric acid leaching is completed.

[0020] The preferred method for the comprehensive treatment of arsenic-containing flue dust is to pyrometallurgically smelt the leaching residue obtained in step (2) to recover lead and tin.

[0021] In the above-mentioned comprehensive treatment method for arsenic-containing flue dust, preferably, the indium-containing leachate obtained in step (1) is subjected to P204 extraction to separate indium, resulting in an indium-containing organic phase and a raffinate. The indium-containing organic phase is back-extracted with hydrochloric acid solution to obtain an indium-containing back-extracted solution. The indium-containing back-extracted solution is neutralized with caustic soda flakes, and the neutralized solution is subjected to cyclone electrodeposition to obtain refined indium. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium.

[0022] The preferred method for the comprehensive treatment of arsenic-containing soot described above includes the following process: the pH value of the electrodeposition solution is 1.5 to 2.3, the current density is 60 to 100 A / m2, the electrodeposition temperature is 30 to 50°C, the electrodeposition time is 24 to 48 h, and the circulation flow rate is 200 to 400 L / h.

[0023] In the technical solution of this invention, low-temperature roasting of high-arsenic flue dust with an arsenic removal agent can achieve the separation of arsenic from valuable metals in the flue dust. The main reaction principle is that the added arsenic removal agent reacts with the arsenic in the high-arsenic flue dust to form low-boiling-point arsenic compounds that volatilize into the flue dust for arsenic enrichment and recovery, thereby achieving the separation of arsenic from valuable metals. The specific reaction is as follows:

[0024] Na2S2O8(heated) + H2O = H2SO4 + O3(g) + SO2(g) + Na2SO4 (1-1);

[0025] As2S3+9H2SO4=As2O3+12SO2(g)+9H2O (1-2);

[0026] As2O5+SO2(g)+H2O=As2O3+H2SO4 (1-3);

[0027] Pb3(AsO4)2+3H2SO4=3PbSO4+2H3AsO4 (1-4);

[0028] Zn3(AsO4)2+3H2SO4=3ZnSO4+2H3AsO4 (1-5);

[0029] Cd3(AsO4)2+3H2SO4=3CdSO4+2H3AsO4 (1-6);

[0030] In2O3+3H2SO4=In2(SO4)3+3H2O (1-7);

[0031] Pb3(AsO4)2+3NaHSO4=3PbSO4+3NaHAsO4 (1-8);

[0032] Zn3(AsO4)2+NaHSO4=3ZnSO4+3NaHAsO4 (1-9);

[0033] Cd3(AsO4)2+3NaHSO4=3CdSO4+3NaHAsO4 (1-10);

[0034] In2O3+3NaHSO4=In2(SO4)3+3NaOH (1-11);

[0035] 2H3AsO4=H4As2O7+H2O (1-12);

[0036] 2H4As2O7=4HAsO3+2H2O (1-13);

[0037] 2HAsO3=As2O5+H2O (1-14);

[0038] As2O3+H2SO4=As2O3·2SO3(g)+2H2O (1-15).

[0039] Compared with the prior art, the advantages of the present invention are as follows:

[0040] (1) This invention uses persulfate and hydrogen sulfate as arsenic removal agents. During the low-temperature roasting process, the arsenic removal agents slowly release H2SO4 and SO2. H2SO4 and SO2 react with arsenic compounds in the flue ash to generate volatile As2O3, thereby achieving the arsenic removal effect. This solves the problems of acid mist that easily generates during the low-temperature roasting arsenic removal process using concentrated sulfuric acid in traditional processes, which seriously pollutes the environment and corrodes equipment. The entire process of this invention is cleaner and more environmentally friendly.

[0041] (2) The present invention uses low-temperature roasting to remove arsenic so that arsenic is further enriched. The high-arsenic flue dust can be directly reduced and smelted with iron slag to prepare arsenic-iron alloy, realizing the resource utilization of arsenic and solving the technical defects of wet process treatment that easily generates arsenic-containing solid waste.

[0042] (3) In the arsenic removal process of the present invention, the arsenic removal rate reaches more than 95% and the indium loss rate does not exceed 3%, realizing the efficient separation of arsenic from other valuable metals in flue dust. This allows valuable metals such as lead, zinc, cadmium, antimony, and indium in flue dust to be comprehensively recovered through wet process. After arsenic enrichment, it can be reduced and smelted with iron slag to prepare arsenic-iron alloy for sale. This enables the harmless disposal and resource utilization of hazardous solid waste containing arsenic in flue dust, providing a new approach to the treatment of arsenic-containing materials.

[0043] (4) This invention adopts a method that combines low-temperature roasting pre-arsenic removal with wet acid leaching of valuable metals such as zinc, cadmium, and indium, which solves the problem of producing a large amount of arsenic-containing solid waste when treating arsenic-containing flue dust with full wet acid leaching, reduces the pollution and harm of arsenic-containing solid waste to the environment, and provides a cleaner and more environmentally friendly approach to the treatment of arsenic-containing flue dust.

[0044] In summary, the process of this invention achieves the separation and comprehensive recycling of arsenic from arsenic-containing flue dust with other valuable metals. It solves the problems of severe acid mist pollution and equipment corrosion caused by concentrated sulfuric acid roasting, as well as the problem of large amounts of arsenic-containing solid waste generated by wet treatment of arsenic-containing flue dust. This provides a new solution for the comprehensive recycling of arsenic-containing flue dust. Attached Figure Description

[0045] Figure 1 This is a flowchart of the comprehensive treatment process for arsenic-containing flue dust according to the present invention. Detailed Implementation

[0046] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0049] Example 1:

[0050] The composition of the arsenic-containing flue dust processed in this embodiment is listed in Table 1 below.

[0051] Table 1. Composition of Arsenic-Containing Flue Ash

[0052]

[0053] A comprehensive treatment method for arsenic-containing flue dust according to the present invention includes the following steps:

[0054] (1) Take 50g of arsenic-containing flue ash to be treated and put it into a porcelain boat, then add 50g of sodium persulfate and mix it thoroughly with the flue ash.

[0055] (2) The ceramic boat containing the mixed material obtained in step (1) is loaded into a tube furnace and calcined at 450°C for 2 hours in an air atmosphere to obtain high arsenic dust and calcined slag. The high arsenic dust is collected and mixed with iron slag for reduction smelting of arsenic-iron alloy. The calcined slag is taken for analysis of As and In.

[0056] (3) The roasted residue obtained in step (2) was added to sulfuric acid solution at a liquid-solid mass ratio of 5:1 for leaching. The reaction was carried out by stirring in a water bath at 80°C for 2 hours. The final acidity of the sulfuric acid leaching was 100 g / L. After the reaction was completed, liquid-solid separation was carried out to obtain indium-containing leaching solution and leaching residue. The indium-containing leaching solution was tested for As and In, and the leaching residue was tested for As and In.

[0057] (4) The obtained leaching residue is subjected to pyrometallurgical smelting to recover valuable metals such as lead and tin; the indium-containing leachate is extracted and separated from indium using P204 extraction to obtain an indium-containing organic phase and raffinate. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium. The indium-containing organic phase is back-extracted using a 6 mol / L hydrochloric acid solution to obtain an indium-containing back-extracting solution. The obtained indium-containing back-extracting solution is neutralized to pH 2.0 with caustic soda, and then subjected to cyclone electrodeposition using a titanium rod coated with IrO2-Ta2O5 as the anode and a 316L stainless steel sheet as the cathode, with the current density controlled at 60 A / m. 2 The temperature was 30℃, the circulation flow rate was 300L / h, the electrodeposition time was 24h, and then the obtained cathode product was washed three times with low concentration hydrochloric acid and deionized water, and then dried in a vacuum drying oven at 60℃ for 5h. Samples were taken for analysis.

[0058] The test results for each process in this embodiment are shown in Table 2.

[0059] Table 2 Technical specifications for each process in Example 1

[0060]

[0061] As can be seen from the experimental results in Table 2, in the low-temperature roasting of this embodiment, the volatilization rate of arsenic was 96.84%, and the arsenic content in the roasting residue was 0.31%, indicating that the addition of sodium persulfate can enable arsenic to volatilize fully. At the same time, the loss rate of indium also reached 31.90%, indicating that the volatilization rate of indium was also very high, which is not conducive to the recovery of indium. The purity of indium in the refined indium obtained by cyclone electrowinning was 99.99%.

[0062] Example 2:

[0063] The arsenic-containing flue dust processed in this embodiment has the same composition as that in Example 1.

[0064] A comprehensive treatment method for arsenic-containing flue dust according to the present invention is shown in the process flow diagram below. Figure 1 As shown, it includes the following steps:

[0065] (1) Take 50g of arsenic-containing flue ash to be treated and put it into a porcelain boat. Then add 50g of sodium persulfate and 20g of sodium bisulfate and mix them thoroughly with the flue ash.

[0066] (2) The ceramic boat containing the mixed material obtained in step (1) is loaded into a tube furnace and calcined at 450°C for 2 hours in an air atmosphere to obtain high arsenic dust and calcined slag. The high arsenic dust is collected and mixed with iron slag for reduction smelting of arsenic-iron alloy. The calcined slag is taken for analysis of As and In.

[0067] (3) The roasted residue obtained in step (2) was added to sulfuric acid solution at a liquid-solid mass ratio of 5:1 for leaching. The reaction was carried out by stirring in a water bath at 80°C for 2 hours. The final acidity of the sulfuric acid leaching was 100 g / L. After the reaction was completed, liquid-solid separation was carried out to obtain indium-containing leaching solution and leaching residue. The indium-containing leaching solution was tested for As and In, and the leaching residue was tested for As and In.

[0068] (4) The obtained leaching residue is subjected to pyrometallurgical smelting to recover valuable metals such as lead and tin; the indium-containing leachate is extracted and separated from indium using P204 extraction to obtain an indium-containing organic phase and raffinate. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium. The indium-containing organic phase is back-extracted using a 6 mol / L hydrochloric acid solution to obtain an indium-containing back-extracting solution. The obtained indium-containing back-extracting solution is neutralized to pH 2.0 with caustic soda, and then subjected to cyclone electrodeposition using a titanium rod coated with IrO2-Ta2O5 as the anode and a 316L stainless steel sheet as the cathode, with the current density controlled at 60 A / m. 2 The temperature was 30℃, the circulation flow rate was 300L / h, the electrodeposition time was 24h, and then the obtained cathode product was washed three times with low concentration hydrochloric acid and deionized water, and then dried in a vacuum drying oven at 60℃ for 5h. Samples were taken for analysis.

[0069] The test results for each process in this embodiment are shown in Table 3.

[0070] Table 3 Technical indicators of each process in Example 2

[0071]

[0072] As can be seen from the experimental results in Table 3, in the low-temperature roasting of this embodiment, the arsenic volatilization rate was 97.52%, and the arsenic content in the roasting residue was 0.21%, indicating that the addition of sodium persulfate can enable arsenic to volatilize fully. At the same time, the indium loss rate was 2.19%, indicating that the addition of sodium bisulfate effectively inhibited the volatilization of indium. Sodium persulfate and sodium bisulfate can work synergistically, which is beneficial to the efficient separation and recovery of arsenic and indium. Meanwhile, the purity of indium in the refined indium obtained by cyclone electrowinning was 99.99%.

[0073] Example 3

[0074] The composition of the arsenic-containing flue dust to be treated in this embodiment is listed in Table 4 below.

[0075] Table 4. Arsenic-containing flue ash composition

[0076]

[0077] A comprehensive treatment method for arsenic-containing flue dust according to the present invention is shown in the process flow diagram below. Figure 1 As shown, it includes the following steps:

[0078] (1) Take 50g of arsenic-containing flue ash to be treated and put it into a porcelain boat. Then add 30g of sodium persulfate and 20g of sodium bisulfate and mix them thoroughly with the flue ash.

[0079] (2) The ceramic boat containing the mixed material obtained in step (1) is loaded into a tube furnace and calcined at 400°C for 2 hours in an air atmosphere to obtain high arsenic dust and calcined slag. The high arsenic dust is collected and mixed with iron slag for reduction smelting of arsenic-iron alloy. The calcined slag is taken for analysis of As and In.

[0080] (3) The roasted residue obtained in step (2) was added to sulfuric acid solution at a liquid-solid mass ratio of 5:1 for leaching. The reaction was carried out by stirring in a water bath at 80°C for 1 hour. The final acidity of the sulfuric acid leaching was 120 g / L. After the reaction was completed, liquid-solid separation was carried out to obtain indium-containing leaching solution and leaching residue. The indium-containing leaching solution was tested for As and In, and the leaching residue was tested for As and In.

[0081] (4) The obtained leaching residue is subjected to pyrometallurgical smelting to recover valuable metals such as lead and tin; the indium-containing leachate is extracted with P204 to separate indium, resulting in an indium-containing organic phase and raffinate. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium. The indium-containing organic phase is back-extracted with 6 mol / L hydrochloric acid solution to obtain an indium-containing back-extracting solution. The obtained indium-containing back-extracting solution is neutralized with caustic soda to a pH of 2.3, and then subjected to cyclone electrodeposition. A titanium rod coated with IrO2-Ta2O5 is used as the anode, and a 316L stainless steel sheet is used as the cathode. The current density is controlled at 80 A / m. 2 The temperature was 30℃, the circulation flow rate was 350L / h, the electrodeposition time was 24h, and then the obtained cathode product was washed three times with low concentration hydrochloric acid and deionized water, and then dried in a vacuum drying oven at 60℃ for 5h. Samples were taken for analysis.

[0082] The test results for each process in this embodiment are shown in Table 5.

[0083] Table 5 Technical indicators of each process in Example 3

[0084]

[0085] As can be seen from the experimental results in Table 5, the arsenic volatilization rate in the low-temperature roasting of this embodiment was 98.09%, the arsenic content in the roasting residue was 0.36%, and there was no loss of indium. This indicates that roasting arsenic-containing flue dust in an arsenic removal agent composed of sodium persulfate and sodium bisulfate can efficiently separate arsenic and indium, which is beneficial for the efficient separation and recovery of arsenic and indium. At the same time, the purity of indium in the refined indium obtained by cyclone electrowinning was 99.95%.

[0086] Comparative Example 1:

[0087] The arsenic-containing flue dust treated in this comparative example has the same composition as in Example 3.

[0088] This comparative method for treating arsenic-containing flue dust includes the following steps:

[0089] (1) Take 200g of arsenic-containing flue dust, add sulfuric acid solution for one leaching, the leaching temperature is 80℃, the leaching process is stirred in a water bath for 2h, the final acidity is controlled at 100g / L, after the reaction is completed, liquid-solid separation is performed to obtain arsenic-indium-containing leachate and leaching residue, and the As and In in the leachate are tested.

[0090] (2) The leaching residue obtained in step (1) is added to sulfuric acid solution for secondary leaching. The leaching temperature is 80℃. The leaching process is carried out by stirring in a water bath for 2 hours. The final acidity is controlled at 150g / L. After the reaction is completed, liquid-solid separation is performed to obtain arsenic-indium leaching solution and leaching residue. The leaching solution and leaching residue are tested for As and In.

[0091] The test results for each process in this comparative example are shown in Tables 6 and 7.

[0092] Table 6 shows the technical specifications of each process in Comparative Example 1.

[0093]

[0094] Table 7 Results of secondary leaching residue

[0095]

[0096] Therefore, it can be seen that in this comparative example, the arsenic-containing flue dust was directly subjected to two acid leaching processes, resulting in an indium leaching rate of 89.35% and an arsenic leaching rate of 51.16%. The arsenic content in the leachate reached over 15 g / L, making subsequent treatment of the arsenic-containing solution a significant challenge. At the same time, the arsenic content in the leaching residue also reached over 25%, which would further enrich the arsenic during subsequent pyrometallurgical treatment, making safe and effective disposal impossible. Furthermore, the arsenic was not effectively enriched but dispersed in the solution and leaching residue, posing a serious threat to the environment.

[0097] Comparative Example 2:

[0098] The arsenic-containing flue dust used in this comparative example has the same composition as that in Example 3.

[0099] This comparative method for treating arsenic-containing flue dust includes the following steps:

[0100] (1) Take 50g of arsenic-containing flue ash and put it into a porcelain boat. Then slowly add 50mL of concentrated sulfuric acid into the porcelain boat and mix it thoroughly with the flue ash.

[0101] (2) The mixture from step (1) is loaded into a tube furnace and calcined at 400°C for 3 hours in an air atmosphere. After calcination, the calcined residue is taken for analysis of As and In.

[0102] (3) The roasted residue obtained in step (2) was added to sulfuric acid solution at a liquid-solid mass ratio of 5:1 and stirred in a water bath at 80°C for 1 hour. The final acidity of sulfuric acid leaching was 120 g / L. After the reaction was completed, liquid-solid separation was performed to obtain indium-containing leaching solution and leaching residue. The indium-containing leaching solution was tested for As and In, and the leaching residue was tested for As and In.

[0103] (4) The obtained leaching residue is subjected to pyrometallurgical smelting to recover valuable metals such as lead and tin; the indium-containing leachate is extracted with P204 to separate indium, resulting in an indium-containing organic phase and raffinate. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium. The indium-containing organic phase is back-extracted with 6 mol / L hydrochloric acid solution to obtain an indium-containing back-extracting solution. The obtained indium-containing back-extracting solution is neutralized with caustic soda to a pH of 2.3, and then subjected to cyclone electrodeposition. A titanium rod coated with IrO2-Ta2O5 is used as the anode, and a 316L stainless steel sheet is used as the cathode. The current density is controlled at 80 A / m. 2 The temperature was 30℃, the circulation flow rate was 350L / h, the electrodeposition time was 24h, and then the obtained cathode product was washed three times with low concentration hydrochloric acid and deionized water, and then dried in a vacuum drying oven at 60℃ for 5h. Samples were taken for analysis.

[0104] The test results for each process in this embodiment are shown in Table 8.

[0105] Table 8 Technical Indicators of Each Process in Comparative Example 2

[0106]

[0107] As shown in Table 8, the comparative example used concentrated sulfuric acid for pre-arsenic removal, achieving an arsenic removal rate of 94.95% and an indium loss rate of 18.07%. The arsenic removal effect was relatively good throughout the pre-arsenic removal process, but the indium volatility was high, and the indium leaching rate during the subsequent acid leaching process was only 84.69%, which was low. In addition, a large amount of acid mist was generated during the mixing process with concentrated sulfuric acid, which not only polluted the environment but also corroded the equipment.

[0108] In summary, this invention utilizes persulfate, persulfate, and bisulfate as arsenic removal agents in the low-temperature roasting of arsenic-containing flue dust. This process volatilizes and concentrates over 95% of the arsenic into the flue dust for recovery. The roasted residue is then acid-leached, achieving an indium leaching rate exceeding 90%. Simultaneously, the arsenic content in the acid leaching solution is significantly reduced, facilitating indium recovery. Furthermore, this invention utilizes the slow release of H₂SO₄ and SO₂ from the arsenic removal agent during the low-temperature roasting process. These react with arsenic compounds in the flue dust to generate volatile As₂O₃, thus removing arsenic. The entire arsenic removal process is cleaner and more environmentally friendly. This solution addresses the problems of severe environmental pollution and equipment corrosion caused by acid fumes generated during the traditional roasting and arsenic removal process using concentrated sulfuric acid. It achieves efficient separation of arsenic from indium and other valuable metals in arsenic-containing flue dust, enabling the comprehensive recovery of valuable metals such as indium, lead, zinc, cadmium, and antimony from the flue dust through a wet process. The arsenic-rich arsenic alloy prepared by reducing and smelting with iron compounds can be sold externally. This allows for the harmless disposal and resource utilization of hazardous solid waste containing arsenic, providing a new approach to the treatment of arsenic-containing materials.

Claims

1. A comprehensive treatment method for arsenic-containing flue dust, characterized in that, Includes the following steps: (1) Arsenic-containing flue dust and arsenic removal agent are mixed and then calcined at low temperature to obtain high-arsenic flue dust and calcination residue; the arsenic removal agent includes persulfate and hydrogen sulfate, and the mass ratio of arsenic-containing flue dust to persulfate and hydrogen sulfate is 1:(0.4~1):(0.1~0.5); the low-temperature calcination temperature is 300~500℃, the calcination time is 2~4h, and the calcination is carried out in an air atmosphere; (2) The roasted residue is leached with sulfuric acid to obtain an indium-containing leachate and a leaching residue.

2. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, In step (1), the persulfate is one of ammonium persulfate, sodium persulfate, and potassium persulfate; The bisulfate is either sodium bisulfate or potassium bisulfate.

3. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, In step (1), the main components of the arsenic-containing dust to be treated, by mass percentage, include: As 10~50%, In 0.4~5%, Pb 10~20%, Zn 5~10%, Cd 5~15%, Sb 5~10%, Sn 1~5%, and moisture 0.1~25%.

4. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, The high-arsenic dust obtained in step (1) was mixed with iron slag and then reduced and smelted to prepare arsenic-iron alloy.

5. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, In step (2), during the sulfuric acid leaching process, the liquid-solid mass ratio is 3:5~1, the leaching temperature is 60~80℃, the leaching time is 1~3h, and the acidity in the solution is 100~150g / L when the sulfuric acid leaching is finished.

6. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, The leaching residue obtained in step (2) is then subjected to pyrometallurgical smelting to recover lead and tin.

7. The comprehensive treatment method for arsenic-containing flue dust as described in claim 1, characterized in that, The indium-containing leachate obtained in step (1) is subjected to P204 extraction to separate indium, resulting in an indium-containing organic phase and a raffinate. The indium-containing organic phase is back-extracted with hydrochloric acid solution to obtain an indium-containing back-extracted solution. The indium-containing back-extracted solution is neutralized with caustic soda flakes, and the neutralized solution is subjected to cyclone electrodeposition to obtain refined indium. The raffinate is returned to the zinc-cadmium recovery system to recover zinc and cadmium.

8. The comprehensive treatment method for arsenic-containing flue dust as described in claim 7, characterized in that, The vortex electrodeposition process includes: an electrodeposition solution with a pH of 1.5 to 2.3 and a current density of 60 to 100 A / m. 2 The electrodeposition temperature is 30~50℃, the electrodeposition time is 24~48h, and the circulation flow rate is 200~400 L / h.

Images