Method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid mud

Abstract

The invention provides a method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid mud, and belongs to the technical field of hazardous solid waste harmlessness and comprehensive resource recovery, and the method comprises the following steps: mixing the lead smelting acid mud, an activating agent and water, ball-milling and activating to obtain activated acid mud; carrying out low-acid oxidation leaching on the activated acid mud to obtain low-acid leaching liquid and low-acid leaching residues; carrying out high-acid oxidation leaching on the low-acid leaching residues to obtain high-acid leaching liquid; bismuth powder is added into the low-acid leaching liquid for tellurium enrichment reaction, and tellurium concentrate and tellurium enriched liquid are obtained; adding chlorine salt into the tellurium-enriched liquid, and reacting under a certain pH value to obtain bismuth oxychloride and bismuth-removed liquid; carrying out mercury enrichment on the bismuth removal liquid to obtain mercury-rich slag and mercury removal liquid; and adding a reducing agent into the mercury removal liquid to react to obtain crude selenium and reduced liquid. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid mud provided by the invention is economical, efficient and environment-friendly, and can solve the problems that the acid mud containing elements such as selenium, tellurium, mercury, silver and lead is stockpiled, all valuable elements cannot be recovered, and the like.

Description

Technical Field

[0001] This invention relates to the field of hazardous solid waste harmless treatment and comprehensive resource recycling technology, and in particular to a method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting acid sludge. Background Technology

[0002] In lead smelting, lead concentrate is first roasted at high temperatures. Most of the volatile elements in the lead concentrate, such as mercury (Hg) and selenium (Se), volatilize into the flue gas, while a small amount of lead, silver, and tellurium are carried into the flue dust. Gaseous mercury in the flue gas reacts with other elements to form mercury-containing compounds. To ensure the quality of sulfuric acid and the activity of the catalyst, the flue gas needs to be captured in a dynamic wave scrubber during the purification process before entering the sulfuric acid workshop. The solid material containing elements such as selenium, tellurium, mercury, silver, and lead obtained from this capture is commonly known as acid sludge. The content of these elements in the acid sludge varies depending on the types and amounts of impurities in the raw lead concentrate. As the production of acid sludge increases, its storage becomes more difficult, posing a significant environmental threat. Furthermore, international environmental treaties classify mercury-containing acid sludge as a hazardous waste.

[0003] Improper treatment of acid sludge can easily lead to environmental pollution from mercury, selenium, and lead, and also waste rare and precious metals such as selenium, silver, and tellurium. Furthermore, the treatment technology or principle will vary significantly depending on the content, phase, and constituent elements of the acid sludge. Therefore, there is an urgent need to develop a method that can safely and environmentally treat acid sludge while efficiently recovering valuable elements such as selenium, tellurium, mercury, silver, and lead. Currently, the methods for comprehensively recovering selenium, mercury, and lead from acid sludge are as follows:

[0004] The invention patent ZL 201710211864.1 describes a method for extracting mercury from heavy acid sludge. The method involves reacting the heavy acid sludge in a hydrochloric acid system with potassium chlorate as an oxidant under specific temperature conditions to obtain a mixture containing mercuric chloride. The mixture is then neutralized and separated to obtain mercuric oxide precipitate and a Na2SeO3 solution. The selenium-containing solution is then fed into a selenium separation system to recover selenium. The mercuric oxide precipitate is dried and then continuously vacuum distilled and condensed to obtain refined mercury. This method employs a wet process, achieving efficient separation of mercury and selenium. High-purity mercury is then produced through continuous vacuum distillation, avoiding the flue gas pollution caused by direct roasting of the acid sludge. However, this method suffers from the significant impact of volatile hydrochloric acid on the operating environment and the high equipment requirements of the hydrochloric acid system. Furthermore, this method only involves the recovery of valuable elements mercury and selenium.

[0005] The invention patent "A Method for Recovering Selenium, Mercury, Gold, and Silver from Acid Sludge" (201510259346.8) describes a method for recovering selenium and mercury from acid sludge by roasting the acid sludge under a protective atmosphere to separate mercury selenide. Gold and silver are then extracted from the roasting residue using a cyanide method. This invention is characterized by its simple process, high product added value, high purity, high recovery rate of valuable elements, and low environmental pollution. However, this method uses the highly toxic substance cyanide, and the acid sludge does not contain elements such as lead or tellurium.

[0006] The invention patent CN 111926187A describes a method for the comprehensive recovery of selenium, mercury, lead, and silver from acid sludge. Lead is separated and enriched from acid sludge through phase transformation with sodium carbonate and selective leaching with dilute sulfuric acid. Selenium, mercury, and silver are separated from the acid sludge through oxidant and acid chlorination leaching. The selenium and mercury leaching solution is then separated by sulfur dioxide reduction to obtain crude selenium. The subsequent mercury-containing solution is used to prepare mercuric sulfide using a sulfiding agent. This method achieves the comprehensive recovery of selenium, mercury, lead, and silver by gradually separating and enriching valuable metals from acid sludge. However, this method uses nitric acid or hydrochloric acid. Hydrochloric acid is volatile and has a significant impact on the operating environment, and the hydrochloric acid system requires high-performance equipment. Nitric acid is easily decomposed to generate toxic nitrogen oxides, polluting the environment and also requiring high-performance equipment. Furthermore, acid sludge does not contain tellurium.

[0007] Current technologies for recovering acid sludge mainly focus on the comprehensive recovery of mercury, selenium, and lead, while the recovery of silver and tellurium is rarely addressed. Because some elements among selenium, tellurium, mercury, silver, and lead form complex phases and interact with each other, current technologies cannot achieve the comprehensive recovery of selenium, tellurium, mercury, silver, and lead, resulting in the waste of existing resources and environmental pollution.

[0008] Therefore, there is an urgent need for an economical and efficient treatment method for acid sludge containing elements such as selenium, tellurium, mercury, silver, and lead, which can solve the problems of acid sludge storage and monetization, as well as the recovery of all elements in the acid sludge and is environmentally friendly. Summary of the Invention

[0009] The technical problem to be solved by this invention is to provide an economical, efficient and environmentally friendly method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting acid sludge, thereby solving the problems of stockpiling and monetizing acid sludge containing elements such as selenium, tellurium, mercury, silver and lead and the full recovery of its valuable elements.

[0010] To address the aforementioned technical problems, this invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting sludge, comprising the following steps:

[0011] Activated ball milling: The acid mud from lead smelting, the activator and water are mixed and ball-milled to obtain activated acid mud;

[0012] Low-acid oxidative leaching: Activated acid mud is added to sulfuric acid and an oxidant is introduced for low-acid oxidative leaching. At the end of the leaching, the low-acid leachate and low-acid leachate residue are obtained by filtration.

[0013] High acid oxidative leaching: The low acid leaching residue is added to sulfuric acid and a strong oxidizing agent is added for high acid oxidative leaching. The high acid leaching solution and high acid leaching residue are obtained by filtration at the leaching endpoint.

[0014] Tellurium enrichment: Bismuth powder is added to a low-acid leaching solution to carry out a reaction. At the end of the reaction, the solution is filtered to obtain tellurium concentrate and tellurium enriched solution.

[0015] Bismuth separation: Chloride salt and neutralizing agent are added to the tellurium enrichment solution to adjust the pH of the solution and carry out the reaction. At the end of the reaction, bismuth oxychloride and bismuth-removed solution are obtained by filtration.

[0016] Mercury enrichment: The pH of the bismuth removal solution is adjusted with a neutralizing agent to enrich mercury, and then filtered to obtain mercury-rich slag and mercury removal solution;

[0017] Selenium reduction: Sulfuric acid is added to the mercury removal solution to adjust the acidity, and then a reducing agent is added to carry out the reaction. At the end of the reaction, the crude selenium and the reduced solution are obtained by filtration.

[0018] Further, the chemical composition of the lead smelting acid sludge, by mass percentage, includes Se: 30-60%, Pb: 5-23%, Hg: 4-19%, Te: 0.85-10.63%, Ag: 0.02-0.50%, S: approximately 2-4%, C: 0.1-0.3%, As: approximately 0.05-0.15%, and Zn and Tl less than 0.05%. Selenium in the lead smelting acid sludge exists in the form of lead selenide, mercuric selenide, selenate, selenium dioxide, and elemental selenium, with elemental selenium accounting for 60-95% of the total selenium content. Tellurium in the lead smelting acid sludge exists in the form of lead telluride, mercuric telluride, tellurate, tellurium dioxide, and elemental tellurium, with elemental tellurium accounting for 64-97% of the total tellurium content.

[0019] Furthermore, the activated acid sludge obtained by ball milling activation contains more than 85% solid particles with a particle size of 240 mesh, the activator is one or a mixture of two of NaClO, KClO, NaClO3 or KClO3, the amount of activator added is 3-10% of the mass of the lead smelting acid sludge, and the mass ratio of the lead smelting acid sludge to water is 1:2-1:3.

[0020] Furthermore, the mass ratio of the activated acid mud to sulfuric acid is 1:5-1:8, the leaching temperature of the activated acid mud is 75-85℃, the leaching time is 2-5h, the mass-volume concentration of sulfuric acid at the endpoint of the low-acid oxidation leaching is 35-65g / L, and the oxidant is oxygen or air.

[0021] Furthermore, the mass ratio of the low-acid leaching residue to sulfuric acid is 1:3-1:5, the leaching temperature of the low-acid leaching residue is 90-95℃, the leaching time is 6-9h, the mass-volume concentration of sulfuric acid at the endpoint of the high-acid oxidative leaching is 85-120g / L, and the strong oxidant is NaClO3, KClO3, NaClO4, or KClO4.

[0022] Furthermore, the reaction temperature between the low-acid leaching solution and the bismuth powder is 82-92℃, the reaction time is 5.5-7.5h, the amount of bismuth powder added is 1.6-2.4 times the mass of tellurium in the low-acid leaching solution, and the medium particle size of the bismuth powder is 63-95μm.

[0023] Further, the tellurium-enriched solution is heated to 65-85℃ and chloride salt is added. The amount of chloride salt added is 1.02-1.08 times the number of moles of bismuth in the tellurium-enriched solution. The chloride salt is sodium chloride or potassium chloride. The neutralizing agent adjusts the pH of the solution to 0.8-2.0. The neutralizing agent is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L. The reaction time for adding chloride salt to the tellurium-enriched solution is 90-180 min.

[0024] Furthermore, the neutralizing agent adjusts the pH of the bismuth removal solution to 6-10 for mercury enrichment, and the mercury enrichment time is 4-6 hours. The neutralizing agent is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L.

[0025] Furthermore, sulfuric acid is added to the mercury removal solution to adjust the acidity of the sulfuric acid in the mercury removal solution to 5-30 g / L, the amount of reducing agent added is 1.1-1.8 times the theoretical mass of selenium in the mercury removal solution, the reaction temperature of the mercury removal solution and the reducing agent is 20-90℃, the reaction time is 5.5-8.5 h, and the reducing agent is sodium sulfite or sulfur dioxide.

[0026] Furthermore, the high-acid leaching residue is lead-silver slag enriched with lead and silver, and the lead-return main system recovers lead and silver; the tellurium concentrate is recovered and refined into tellurium products in the tellurium return process; the bismuth oxychloride can be sold to zinc smelting enterprises as raw materials for dechlorination; the mercury-rich slag can be refined into mercury products through reduction and distillation processes or sold directly; the crude selenium can be recovered and refined into refined selenium products in the selenium return process.

[0027] This invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting acid sludge. This method not only solves the problem of stockpiling hazardous solid waste like lead smelting acid sludge, but also comprehensively and effectively recovers valuable elements such as selenium, tellurium, mercury, silver, and lead from the sludge. The recovery rates of lead and silver in lead smelting acid sludge exceed 99.5%, and the recovery rates of selenium, mercury, and tellurium reach 99.2%, 99.1%, and 91.5%, respectively. This not only solves the resource waste and environmental problems caused by the stockpiling of lead smelting acid sludge, but also revitalizes the economy and improves economic efficiency.

[0028] Furthermore, this invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting acid sludge. In order to maximize the recovery of valuable elements in lead smelting acid sludge and turn waste into treasure, activated ball milling and two-stage leaching are adopted. Moreover, the recovery method provided by this invention uses conventional reagents and conventional equipment. At the same time, it utilizes the company's existing lead, silver, and tellurium production capacity to process the corresponding materials, thereby reducing investment costs and subsequent production costs.

[0029] Meanwhile, this invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting acid sludge. It innovatively uses bismuth as a raw material to remove tellurium from lead smelting acid sludge, and produces bismuth oxychloride product while obtaining tellurium concentrate. This product can be used as a material for dechlorination in zinc smelting and other enterprises, which greatly improves the utilization efficiency of hazardous solid waste.

[0030] Therefore, this invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting sludge. This method is not only simple and reasonable, but also fully utilizes existing lead, tellurium, and silver production systems to produce corresponding lead alloys, silver ingots, refined tellurium, refined selenium, and metallic mercury products. It completely solves the problem of hazardous solid waste storage and simultaneously improves the capital turnover of valuable metals in lead smelting sludge, thus increasing economic efficiency. Furthermore, the process of this invention does not generate new waste, making it environmentally friendly and conforming to green production, resource recycling, and sustainable development requirements. It is industrially feasible and has a very broad application prospect. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting acid sludge, as provided in an embodiment of the present invention. Detailed Implementation

[0032] See Figure 1 The present invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting acid sludge, comprising the following steps:

[0033] Step 1) Activation ball milling: Mix lead smelting acid mud, activator and water and ball mill to activate acid mud.

[0034] The chemical composition of the lead smelting acid mud, by mass percentage, includes Se: 30-60%, Pb: 5-23%, Hg: 4-19%, Te: 0.85-10.63%, Ag: 0.02-0.50%, S: approximately 2-4%, C: 0.1-0.3%, As: approximately 0.05-0.15%, and Zn and Tl less than 0.05%.

[0035] In this case, selenium exists in the lead smelting acid sludge in the form of lead selenide, mercuric selenide, selenate, selenium dioxide, and elemental selenium, and elemental selenium accounts for 60-95% of the total selenium content.

[0036] The tellurium in the lead smelting acid sludge exists in the form of lead telluride, mercuric telluride, tellurate, tellurium dioxide, and elemental tellurium, and elemental tellurium accounts for 64-97% of the total tellurium content in the lead smelting acid sludge.

[0037] In this process, lead smelting acid sludge, activator, and water are ball-milled and refined in a ball mill. At the same time, compounds such as selenium and tellurium in the lead smelting acid sludge are activated during the ball milling process to obtain activated acid sludge.

[0038] The activator is one or a mixture of two of NaClO, KClO, NaClO3 or KClO3, and the amount of activator added is 3-10% of the mass of lead smelting acid mud. The mass ratio of lead smelting acid mud to water is 1:2-1:3.

[0039] Furthermore, the activated acid mud obtained from the activation process contains more than 85% solid particles with a particle size greater than 240 mesh.

[0040] Step 2) Low-acid oxidative leaching: Add activated acid mud to sulfuric acid and pass an oxidant through for low-acid oxidative leaching. Filter at the leaching endpoint to obtain low-acid leachate and low-acid leachate residue.

[0041] The mass ratio of activated acid mud to sulfuric acid is 1:5-1:8, the leaching temperature of activated acid mud is 75-85℃, the leaching time is 2-5h, and the mass volume concentration of sulfuric acid at the low acid oxidation leaching endpoint is 35-65g / L.

[0042] In the process of leaching activated acid mud in low acid oxidation, the oxidant introduced is oxygen or air.

[0043] In the low-acid oxidation leaching process of activated acid mud, not only does the oxidant oxygen or oxygen in the air participate in the oxidation reaction, but also a portion of the unreacted residual activator NaClO, KClO, NaClO3, or KClO3 used in step 1) also participates as an oxidant in the low-acid oxidation of the activated acid mud. The reactions that occur in this process are as follows:

[0044] 2PbSe+3O2+2H2SO4=2PbSO4↓+2H2SeO3

[0045] 2HgSe+3O2+2H2SO4=2HgSO4+2H2SeO3

[0046] PbSe+6NaClO3+4H2SO4=3Na2SO4+PbSO4↓+6ClO2↑+3H2O+H2SeO3

[0047] HgSe+6NaClO3+4H2SO4=3Na2SO4+HgSO4+6ClO2↑+3H2O+H2SeO3

[0048] Se + O₂ + H₂O = H₂SeO₃

[0049] Se+4NaClO3+2H2SO4=4ClO2↑+2Na2SO4+H2O+H2SeO3

[0050] SeO2 + H2O = H2SeO3

[0051] 2SeO2 + O2 + 2H2O = 2H2SeO4

[0052] 2H₂SeO₃ + O₂ = 2H₂SeO₄

[0053] 2PbTe+3O2+2H2SO4=2PbSO4↓+2H2TeO3

[0054] 2HgTe+3O2+2H2SO4=2HgSO4+2H2TeO3

[0055] PbTe+6NaClO3+4H2SO4=3Na2SO4+PbSO4↓+6ClO2↑+3H2O+H2TeO3

[0056] HgTe+6NaClO3+4H2SO4=3Na2SO4+HgSO4+6ClO2↑+3H2O+H2TeO3

[0057] Te + O₂ + H₂O = H₂TeO₃

[0058] Te+4NaClO3+2H2SO4=4ClO2↑+2Na2SO4+H2O+H2TeO3

[0059] 2TeO2 + O2 + 2H2O = 2H2TeO4

[0060] 2H₂TeO₃ + O₂ = 2H₂TeO₄

[0061] Pb + H₂SO₄ = H₂↑ + PbSO₄↓

[0062] 2Pb + O₂ = 2PbO

[0063] PbO + H₂SO₄ = H₂O + PbSO₄↓

[0064] Hg + H₂SO₄ = H₂↑ + HgSO₄↓

[0065] Hg + O2 = 2HgO

[0066] HgO + H₂SO₄ = H₂O + HgSO₄

[0067] Step 3) High acid oxidation leaching: Add the low acid leaching residue to sulfuric acid and add a strong oxidizing agent for high acid oxidation leaching. Filter at the leaching endpoint to obtain high acid leaching solution and high acid leaching residue.

[0068] The resulting high-acid leachate can be returned to the low-acid oxidative leaching in step 2) as a leachate to continue leaching the activated acid mud. The resulting high-acid leaching residue is lead-silver slag enriched with lead and silver, which can be returned to the main lead system to recover the lead and silver.

[0069] The mass ratio of low-acid leaching residue to sulfuric acid is 1:3-1:5. The leaching temperature of the low-acid leaching residue under the action of sulfuric acid and strong oxidant is 90-95℃, and the leaching time is 6-9h.

[0070] The strong oxidizing agent is NaClO3, KClO3, NaClO4, or KClO4.

[0071] The mass-volume concentration of sulfuric acid at the endpoint of high-acid oxidative leaching is 85-120 g / L.

[0072] The following chemical reactions mainly occur in the low-acid leaching residue during the high-acid oxidative leaching process:

[0073] PbSe+6NaClO3+4H2SO4=3Na2SO4+PbSO4↓+6ClO2↑+3H2O+H2SeO3

[0074] HgSe+6NaClO3+4H2SO4=3Na2SO4+HgSO4+6ClO2↑+3H2O+H2SeO3

[0075] Se+4NaClO3+2H2SO4=4ClO2↑+2Na2SO4+H2O+H2SeO3

[0076] PbTe+6NaClO3+4H2SO4=3Na2SO4+PbSO4↓+6ClO2↑+3H2O+H2TeO3

[0077] HgTe+6NaClO3+4H2SO4=3Na2SO4+HgSO4+6ClO2↑+3H2O+H2TeO3

[0078] Te+4NaClO3+2H2SO4=4ClO2↑+2Na2SO4+H2O+H2TeO3

[0079] H2SO4+H2TeO3+2NaClO3=2ClO2↑+Na2SO4+H2O+H2TeO4.

[0080] By using a certain temperature and acidity, and under the action of a strong oxidant, after a certain period of strong acid oxidation leaching, valuable elements Se and Te in the low acid leaching residue can be further leached out. The high acid leachate obtained after leaching can be returned to the low acid oxidation leaching in step 2) for further recycling of valuable elements Se and Te in the high acid leaching solution, thereby ensuring a high recovery rate of valuable elements Se and Te.

[0081] Step 4) Tellurium enrichment: Add bismuth powder to the low-acid leaching solution to carry out the reaction. After the reaction is completed, filter to obtain tellurium concentrate and tellurium enriched solution.

[0082] The reaction temperature between the low-acid leachate and bismuth powder is 82-92℃. Specifically, bismuth powder is added to the low-acid leachate at 82-92℃ to enrich tellurium in the leachate. The main chemical reactions occurring during this tellurium enrichment process are as follows:

[0083] H2TeO4+Bi+H2SO4=Bi2Te3+Bi2(SO4)3+H2O

[0084] The amount of bismuth powder added is 1.6-2.4 times the mass of tellurium in the low-acid leaching solution, and in order to achieve a better reaction effect, the medium particle size of the bismuth powder is controlled to be 63-95μm.

[0085] After the tellurium enrichment reaction has proceeded for 5.5-7.5 hours, reaching its endpoint, filtration yields tellurium concentrate and tellurium enrichment liquid. The tellurium concentrate is returned to the tellurium process for recycling and refining into tellurium products, while the tellurium enrichment liquid undergoes the next bismuth separation process.

[0086] Step 5) Bismuth separation: Add chloride salt and neutralizing agent to the tellurium enrichment solution to adjust the pH of the solution and carry out the reaction. At the end of the reaction, filter to obtain bismuth oxychloride and bismuth-removed solution.

[0087] In the bismuth separation process of the tellurium enrichment solution, in order to facilitate the effective separation of bismuth, the tellurium enrichment solution is first heated to 65-85℃, and then chloride salt is added to the tellurium enrichment solution to carry out the reaction. At the same time, in order to make the reaction more effective, after adding chloride salt to the tellurium enrichment solution, a neutralizing agent is added to the solution to adjust the pH value of the solution to 0.8-2.0.

[0088] The amount of chloride added is 1.02-1.08 times the number of moles of bismuth in the tellurium enrichment solution.

[0089] Among them, the chloride salt is sodium chloride or potassium chloride.

[0090] The neutralizing agent added is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L.

[0091] The main chemical reactions that occur during this reaction are as follows:

[0092] 2NaOH + H₂SO₄ = Na₂SO₄ + H₂O

[0093] 2NaCl+2H2O+Bi2(SO4)3=2H2SO4+Na2SO4+2BiClO↓

[0094] After adding chloride salt to the tellurium enrichment solution and reacting for 90-180 minutes, i.e., at the end of the reaction, filtration yields bismuth oxychloride and bismuth-removed solution.

[0095] The obtained bismuth oxychloride can be sold to zinc smelting enterprises as raw material for dechlorination, and the obtained bismuth-free solution will be used for the next mercury enrichment process.

[0096] Step 6) Mercury enrichment: Adjust the pH of the bismuth removal solution with a neutralizing agent to enrich mercury, and then filter to obtain mercury-rich slag and mercury removal solution;

[0097] The neutralizing agent is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L.

[0098] To enrich the mercury in the bismuth removal solution, the pH of the solution is first adjusted with a neutralizing agent to 6-10. After the mercury enrichment time reaches 4-6 hours, the reaction can be stopped and the solution filtered to obtain mercury-rich slag and mercury-removed solution.

[0099] The resulting mercury-rich slag can be sold directly or refined into mercury products through reduction and distillation processes for sale, while the mercury-removed liquid will undergo further selenium reduction.

[0100] Step 7) Selenium reduction: Add sulfuric acid to the mercury removal solution to adjust the acidity, then add a reducing agent to carry out the reaction. At the end of the reaction, filter to obtain crude selenium and the reduced solution.

[0101] To facilitate the reduction of selenium in the mercury removal solution, the acidity of the sulfuric acid in the solution is first adjusted to 5-30 g / L. Then, a reducing agent of 1.1-1.8 times the theoretical mass of selenium in the mercury removal solution is slowly added, controlling the reaction temperature at 20-90℃. After reacting for 5.5-8.5 hours, the solution is filtered to obtain crude selenium and the reduced solution. The crude selenium can be recycled and refined into refined selenium in the selenium return process, while the reduced solution can be used to recover sodium sulfate.

[0102] The reducing agent is sodium sulfite or sulfur dioxide.

[0103] Lead smelting enterprises generate large amounts of SO2 flue gas during the high-temperature roasting of lead concentrate. This flue gas is generally used to produce sulfuric acid. Simultaneously, fuming furnaces also produce dust during the processing of various slags. After treatment and purification by a dust collection system, this also yields SO2 flue gas, which is typically recycled for sulfuric acid production. However, using SO2 flue gas to produce sulfuric acid is costly. Utilizing this SO2 flue gas as a reducing agent in this invention can significantly reduce production costs and eliminates the need for investment in SO2 production equipment.

[0104] Therefore, in a preferred embodiment of the present invention, the reducing agent is SO2 flue gas produced during the high-temperature roasting of lead concentrate, or SO2 flue gas obtained after the dust produced by the slag furnace is treated and purified by the dust collection system.

[0105] The main chemical reactions that occur during the selenium reduction process are as follows:

[0106] H2SeO3+2SO2+H2O=2H2SO4+Se↓

[0107] This invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting acid sludge. In order to maximize the recovery of valuable metals from lead smelting acid sludge and turn waste into treasure, activated ball milling and two-stage sulfuric acid oxidation leaching are adopted. The reagents used in the recovery process are all conventional reagents, and there are no special requirements for the equipment used. Conventional ordinary equipment is used. At the same time, the existing production capacity of lead, silver, and tellurium is utilized to process the corresponding materials, which greatly reduces investment costs and subsequent production costs.

[0108] Furthermore, the present invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting sludge. The process is simple and efficient, and can make full use of existing lead, tellurium, silver and other production systems to produce corresponding lead alloys, silver ingots, refined tellurium, refined selenium and metallic mercury products. Not only is the production cost low, but the purity of the obtained lead alloys, silver ingots, refined tellurium, refined selenium and metallic mercury products is also high.

[0109] Meanwhile, this invention provides a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting acid sludge. This method fully utilizes this hazardous solid waste to comprehensively recover valuable elements such as selenium, tellurium, mercury, silver, and lead, completely solving the problems of resource waste and environmental impact caused by the stockpiling of hazardous solid waste. Furthermore, the recovery process does not generate new waste, making it a green production method that is environmentally friendly, meets the requirements of resource recycling and sustainable development. It has already been industrialized and has a very broad application prospect.

[0110] The following examples illustrate a method for the comprehensive recovery of selenium, tellurium, mercury, silver, and lead from lead smelting sludge provided by the present invention.

[0111] Example 1

[0112] For a lead smelting acid sludge with the following chemical composition: Se 49.67%, Pb 19.48%, Hg 11.55%, Te 2.86%, Ag 0.0946%, and S 3.19%, C 0.2%, As 0.1%, Zn 0.018%, and Tl 0.016%, wherein elemental selenium accounts for 79.18% of the total selenium content and elemental tellurium accounts for 86.36% of the total tellurium content, according to... Figure 1 The process involves the following steps:

[0113] Step 1: Activation ball milling: Add lead smelting acid mud and water in a mass ratio of 1:3, along with 10% NaClO (by mass of the lead smelting acid mud), to a ball mill for activation. The resulting activated acid mud has a particle size of 86.17% that is less than 240 mesh.

[0114] The second step is low-acid oxidation leaching: the activated acid mud is added to the sulfuric acid system at a mass ratio of lead smelting acid mud to solution of 1:8 and leached at a temperature of T=75℃ for t=2h. Oxygen is introduced during the leaching process, and the mass volume concentration of H2SO4 at the leaching endpoint is controlled to be 65g / L. The low-acid leachate and low-acid leaching residue are obtained by filtration at the leaching endpoint.

[0115] The third step is high-acid oxidation leaching: the low-acid leaching residue is leached at a temperature of 90℃ for 9 hours and a mass ratio of low-acid leaching residue to solution of 1:3. A strong oxidant, KClO3, is added during the leaching process. The mass-volume concentration of H2SO4 at the leaching endpoint is 120 g / L. The high-acid leaching solution and high-acid leaching residue are obtained by filtration at the leaching endpoint.

[0116] The fourth step is tellurium enrichment: take the low acid leaching solution and add 1.6 times the theoretical tellurium mass of bismuth powder with a medium particle size of 95μm at a temperature of 92℃. The enrichment time is 5.5h. After the reaction endpoint, filter to obtain tellurium concentrate and tellurium enriched solution.

[0117] Step 5: Bismuth separation: Take the tellurium enriched solution and heat it to 65℃. Add sodium chloride at 1.08 times the molar amount of bismuth in the tellurium enriched solution. Then adjust the pH of the solution to 0.8 with a neutralizing agent. The reaction time is 180 min. At the end of the reaction, filter to obtain bismuth oxychloride and bismuth-removed solution.

[0118] Step 6: Mercury enrichment: Adjust the pH of the solution to 6 using a sodium hydroxide solution with a mass-volume concentration of 120 g / L. The mercury enrichment time is 4 hours. At the end of the reaction, filter to obtain mercury-rich slag and mercury-removed liquid.

[0119] Step 7: Selenium reduction: First, adjust the acidity of sulfuric acid in the mercury removal solution to 30 g / L with sulfuric acid. Then, slowly add sodium sulfite, a reducing agent, at 1.1 times the theoretical amount of selenium to be reduced. The reduction temperature is 20℃, and the reduction time is 8.5 h. After the reaction reaches its end, filter to obtain crude selenium and the reduced solution.

[0120] The high-acid leaching sludge is recycled back to the main lead system to recover lead and silver, yielding lead alloys and silver ingots; the tellurium concentrate is recycled and refined into 99.99% tellurium ingots; mercury-rich slag is refined into metallic mercury through subsequent reduction and distillation processes; and crude selenium is recycled and refined into refined selenium products. Calculations show that the comprehensive recovery rates of lead, silver, selenium, mercury, and tellurium from lead smelting acid sludge to produce their corresponding products are 99.73%, 99.81%, 99.35%, 99.21%, and 92.15%, respectively.

[0121] Example 2

[0122] For a lead smelting acid sludge with the following chemical composition: Se 59.82%, Pb 5.16%, Hg 18.81%, Te 0.94%, Ag 0.473%, and S 3.62%, C 0.23%, As 0.14%, Zn 0.013%, and Tl 0.042%, wherein elemental selenium accounts for 94.75% of the total selenium content and elemental tellurium accounts for 96.18% of the total tellurium content, according to... Figure 1 The process involves the following steps:

[0123] Step 1: Activation ball milling: Add lead smelting acid mud and water in a mass ratio of 1:2, along with 3% KClO3 (by mass of lead smelting acid mud) to a ball mill for activation. The resulting activated acid mud has 88.35% particle size passing through 240 mesh.

[0124] The second step is low-acid oxidation leaching: the activated acid mud is added to the sulfuric acid system at a mass ratio of lead smelting acid mud to solution of 1:5 and leached at a temperature of T=85℃ for t=5h. Air is introduced during the leaching process and the mass volume concentration of H2SO4 at the leaching endpoint is controlled to be 35g / L. The low-acid leachate and low-acid leaching residue are obtained by filtration at the leaching endpoint.

[0125] The third step is high-acid oxidation leaching: the low-acid leaching residue is leached at a temperature of 95℃ for 6 hours and a mass ratio of low-acid leaching residue to solution of 1:5. During the leaching process, strong oxidant NaClO4 is added. The mass-volume concentration of H2SO4 at the leaching endpoint is 85 g / L. After leaching, the high-acid leachate and high-acid leaching residue are obtained by filtration.

[0126] Step 4: Tellurium enrichment: Take the low-acid leaching solution and add 2.4 times the theoretical mass of bismuth powder with a medium particle size of 63μm at a temperature of 82℃. The enrichment time is 7.5h. After the reaction endpoint, filter to obtain tellurium concentrate and tellurium enriched solution.

[0127] Step 5: Bismuth separation: Take the tellurium enriched solution and heat it to 85℃. Add potassium chloride at 1.02 times the number of moles of bismuth in the tellurium enriched solution. Then adjust the pH of the solution to 2.0 with a neutralizing agent. The reaction time is 90 min. Filter at the end of the reaction to obtain bismuth oxychloride and bismuth-removed solution.

[0128] Step 6: Mercury enrichment: Adjust the pH of the solution to 10 using a potassium hydroxide solution with a mass-volume concentration of 40 g / L. The mercury enrichment time is 6 hours. At the end of the reaction, filter to obtain mercury-rich slag and mercury-removed liquid.

[0129] Step 7: Selenium reduction: First, adjust the acidity of sulfuric acid in the mercury removal solution to 5 g / L with sulfuric acid. Then, slowly introduce sulfur dioxide, a reducing agent that is 1.8 times the theoretical amount of selenium to be reduced. The reduction temperature is 90℃ and the reduction time is 5.5 h. After the reaction is completed, filter to obtain crude selenium and the reduced solution.

[0130] The high-acid leaching sludge is recycled back to the main lead system to recover lead and silver, yielding lead alloys and silver ingots; the tellurium concentrate is recycled and refined into 99.99% tellurium ingots; mercury-rich slag is refined into metallic mercury through subsequent reduction and distillation processes; and crude selenium is recycled and refined into refined selenium products. Calculations show that the comprehensive recovery rates of lead, silver, selenium, mercury, and tellurium from lead smelting acid sludge to produce their corresponding products are 99.69%, 99.88%, 99.39%, 99.22%, and 92.83%, respectively.

[0131] Example 3

[0132] For a lead smelting acid sludge with the following chemical composition: Se 31.59%, Pb 22.85%, Hg 4.27%, Te 10.52%, Ag 0.216%, and S 2.81%, C 0.18%, As 0.09%, Zn 0.014%, Tl 0.017%, wherein elemental selenium accounts for 63.18% of the total selenium content and elemental tellurium accounts for 65.11% of the total tellurium content, according to... Figure 1 The process involves the following steps:

[0133] Step 1: Activation ball milling: Add lead smelting acid mud and water in a mass ratio of 1:2.5, along with 7% of the mass of lead smelting acid mud NaClO3, to a ball mill for activation. The resulting activated acid mud has a particle size of 89.84% that is less than 240 mesh.

[0134] The second step is low-acid oxidation leaching: the activated acid mud is added to the sulfuric acid system at a mass ratio of lead smelting acid mud to solution of 1:7 and leached at a temperature of T=80℃ for t=4h. Oxygen is introduced during the leaching process, and the mass volume concentration of H2SO4 at the leaching endpoint is controlled to be 45g / L. The low-acid leachate and low-acid leaching residue are obtained by filtration at the leaching endpoint.

[0135] The third step is high-acid oxidation leaching: the low-acid leaching residue is leached at a temperature of 92℃ for 7 hours and a mass ratio of low-acid leaching residue to solution of 1:4. A strong oxidant, KClO4, is added during the leaching process. The mass-volume concentration of H2SO4 at the leaching endpoint is 100 g / L. The high-acid leaching solution and high-acid leaching residue are obtained by filtration at the leaching endpoint.

[0136] The fourth step is tellurium enrichment: take the low acid leaching solution and add bismuth powder with a medium particle size of 75μm and 2.0 times the theoretical tellurium mass at a temperature of 88℃. The enrichment time is 6.5h. After the reaction endpoint, filter to obtain tellurium concentrate and tellurium enriched solution.

[0137] Step 5: Bismuth separation: Take the tellurium enriched solution and heat it to 75℃. Add sodium chloride at 1.05 times the molar amount of bismuth in the tellurium enriched solution. Then adjust the pH of the solution to 1.5 with a neutralizing agent. The reaction time is 120 min. At the end of the reaction, filter to obtain bismuth oxychloride and bismuth-removed solution.

[0138] Step 6: Mercury enrichment: Adjust the pH of the solution to 8 using a potassium hydroxide solution with a mass-volume concentration of 80 g / L. The mercury enrichment time is 5 h. At the end of the reaction, filter to obtain mercury-rich slag and mercury-removed liquid.

[0139] Step 7: Selenium reduction: First, adjust the acidity of sulfuric acid in the mercury removal solution to 18 g / L with sulfuric acid. Then, slowly introduce sulfur dioxide, a reducing agent that is 1.5 times the theoretical amount of selenium to be reduced. The reduction temperature is 50℃ and the reduction time is 6.5 h. After the reaction is completed, filter to obtain crude selenium and the reduced solution.

[0140] The high-acid leaching sludge is recycled back to the main lead system to recover lead and silver, yielding lead alloys and silver ingots; the tellurium concentrate is recycled and refined into 99.99% tellurium ingots; mercury-rich slag is refined into metallic mercury through subsequent reduction and distillation processes; and crude selenium is recycled and refined into refined selenium products. Calculations show that the comprehensive recovery rates of lead, silver, selenium, mercury, and tellurium from lead smelting acid sludge to produce their corresponding products are 99.58%, 99.95%, 99.86%, 99.90%, and 93.42%, respectively.

[0141] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for the comprehensive recovery of selenium, tellurium, mercury, silver and lead from lead smelting acid sludge, characterized in that, Includes the following steps: Activated ball milling: The acid mud from lead smelting, the activator and water are mixed and ball-milled to obtain activated acid mud; Low-acid oxidative leaching: Activated acid mud is added to sulfuric acid and an oxidant is introduced for low-acid oxidative leaching. At the end of the leaching, the low-acid leachate and low-acid leachate residue are obtained by filtration. High acid oxidative leaching: The low acid leaching residue is added to sulfuric acid and a strong oxidizing agent is added for high acid oxidative leaching. The high acid leaching solution and high acid leaching residue are obtained by filtration at the end of the leaching process. Tellurium enrichment: Bismuth powder is added to a low-acid leaching solution to carry out a reaction. At the end of the reaction, the solution is filtered to obtain tellurium concentrate and tellurium enriched solution. Bismuth separation: Chloride salt and neutralizing agent are added to the tellurium enrichment solution to adjust the pH of the solution and carry out the reaction. At the end of the reaction, bismuth oxychloride and bismuth-removed solution are obtained by filtration. Mercury enrichment: The pH of the bismuth removal solution is adjusted with a neutralizing agent to enrich mercury, and then filtered to obtain mercury-rich slag and mercury removal solution; Selenium reduction: sulfuric acid is added to the mercury removal solution to adjust the acidity, and then a reducing agent is added to carry out the reaction. At the end of the reaction, the crude selenium and the reduced solution are obtained by filtration.

2. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting sludge according to claim 1, characterized in that, The chemical composition of the lead smelting acid sludge, by mass percentage, includes Se: 30-60%, Pb: 5-23%, Hg: 4-19%, Te: 0.85-10.63%, Ag: 0.02-0.50%, S: approximately 2-4%, C: 0.1-0.3%, As: approximately 0.05-0.15%, and Zn and Tl less than 0.05%. Selenium in the lead smelting acid sludge exists in the form of lead selenide, mercuric selenide, selenate, selenium dioxide, and elemental selenium, with elemental selenium accounting for 60-95% of the total selenium content. Tellurium in the lead smelting acid sludge exists in the form of lead telluride, mercuric telluride, tellurate, tellurium dioxide, and elemental tellurium, with elemental tellurium accounting for 64-97% of the total tellurium content.

3. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The activated acid sludge obtained by ball milling activation contains more than 85% solid particles with a particle size of 240 mesh. The activator is one or a mixture of two of NaClO, KClO, NaClO3 or KClO3. The amount of activator added is 3-10% of the mass of the lead smelting acid sludge. The mass ratio of the lead smelting acid sludge to water is 1:2-1:

3.

4. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The mass ratio of activated acid mud to sulfuric acid is 1:5-1:8, the leaching temperature of the activated acid mud is 75-85℃, the leaching time is 2-5h, the mass-volume concentration of sulfuric acid at the endpoint of the low-acid oxidation leaching is 35-65g / L, and the oxidant is oxygen or air.

5. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The mass ratio of the low-acid leaching residue to sulfuric acid is 1:3-1:5, the leaching temperature of the low-acid leaching residue is 90-95℃, the leaching time is 6-9h, the mass-volume concentration of sulfuric acid at the endpoint of the high-acid oxidative leaching is 85-120g / L, and the strong oxidant is NaClO3, KClO3, NaClO4 or KClO4.

6. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The reaction temperature between the low-acid leaching solution and the bismuth powder is 82-92℃, and the reaction time is 5.5-7.5h. The amount of bismuth powder added is 1.6-2.4 times the mass of tellurium in the low-acid leaching solution, and the medium particle size of the bismuth powder is 63-95μm.

7. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The tellurium-enriched solution is heated to 65-85℃ and a chloride salt is added. The amount of chloride salt added is 1.02-1.08 times the molar number of bismuth in the tellurium-enriched solution. The chloride salt is sodium chloride or potassium chloride. The neutralizing agent adjusts the pH of the solution to 0.8-2.

0. The neutralizing agent is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L. The reaction time for adding the chloride salt to the tellurium-enriched solution is 90-180 min.

8. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The neutralizing agent adjusts the pH of the bismuth removal solution to 6-10 for mercury enrichment, and the mercury enrichment time is 4-6 hours. The neutralizing agent is an aqueous solution of sodium hydroxide or potassium hydrochloride with a mass-volume concentration of 40-120 g / L.

9. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting sludge according to claim 1, characterized in that: The sulfuric acid concentration in the mercury removal solution is adjusted to 5-30 g / L by adding sulfuric acid. The amount of reducing agent added is 1.1-1.8 times the theoretical mass of selenium in the mercury removal solution. The reaction temperature between the mercury removal solution and the reducing agent is 20-90℃, and the reaction time is 5.5-8.5 h. The reducing agent is sodium sulfite or sulfur dioxide.

10. The method for comprehensively recovering selenium, tellurium, mercury, silver and lead from lead smelting acid sludge according to claim 1, characterized in that: The high-acid leaching residue is lead-silver slag enriched with lead and silver, and the lead-return main system recovers lead and silver; the tellurium concentrate is recovered and refined into tellurium products in the tellurium return process; the bismuth oxychloride can be sold to zinc smelting enterprises as raw materials for dechlorination; the mercury-rich slag can be refined into mercury products through reduction and distillation processes or sold directly; the crude selenium can be recovered and refined into refined selenium products in the selenium return process.

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