A method for arsenic removal from zinc oxide fume

Abstract

The present invention relates to a method for removing arsenic from zinc oxide fume, belonging to the technical field of treatment of harmful fumes in lead-zinc smelting and chemical production. The present invention includes leaching zinc oxide fume with an alkaline solution, decomposing the solid material, filtering, washing, and drying to obtain arsenic-removed zinc oxide fume; at the same time, the obtained zinc oxide fume leaching solution is added with an arsenic-removing agent to remove arsenic, and CO 2 gas is used for carbonization to remove lead and zinc. Calcium hydroxide is used for conversion reaction, and light calcium carbonate is obtained by precipitation separation, and the leaching solution is converted into sodium hydroxide solution and returned to the leaching process for recycling. The method of the present invention is a method for treating arsenic removal from zinc oxide fume, with simple process and equipment, and is safe and easy to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of harmful smoke treatment in lead and zinc smelting and chemical production, and specifically relates to a method for removing arsenic from zinc oxide smoke. Background Art

[0002] my country is the world's largest producer and consumer of lead and zinc. In recent years, the demand for lead and zinc smelting products has grown rapidly, prompting my country's lead and zinc smelting capacity to increase significantly year by year. my country accounts for more than 40% of the world's lead and zinc smelting production and product consumption. However, with the rapid development of domestic lead and zinc smelting, the limited resources make it difficult to maintain the demand for long-term development. Lead and zinc resources are rapidly consumed, and high-quality resources are decreasing. As the ore grade continues to decrease, low-grade, complex multi-metallic ores are developed and utilized in large quantities, and the arsenic content in the original ore continues to increase, resulting in various impurities in lead and zinc resources, especially harmful elements such as arsenic, entering the lead and zinc smelting process, causing various intermediate materials and slags produced by lead and zinc smelting to contain arsenic, thus forming various arsenic-containing hazardous waste slags.

[0003] Arsenic in lead-zinc concentrate mainly exists in the form of arsenopyrite. During the oxygen-enriched top-blown smelting process of lead concentrate, due to the high temperature and strong oxidizing atmosphere of oxygen-enriched top-blown smelting, arsenopyrite is oxidized and decomposed to form As 2 O 3 and metallic arsenic. As 2 O 3 It volatilizes at high temperature and enters the smoke with the flue gas, forming a large amount of arsenic-containing crude lead smelting smoke; the decomposed metallic arsenic enters the crude lead, and is oxidized into arsenates such as ferric arsenate and enters the lead-rich slag. During the reduction smelting process of the lead-rich slag, about 32% of the arsenic still exists in the reduced slag in the form of arsenates. When the reduced slag is fumed in the fuming furnace, 98% of the total arsenic is reduced and enters the flue gas, and enters the zinc oxide smoke when the zinc oxide smoke is collected, forming arsenic-containing zinc oxide smoke. During the boiling roasting, about 10% of the arsenic in the zinc concentrate is oxidized to As 2 O 3 It enters the smoke and forms a large amount of arsenic-containing zinc oxide smoke.

[0004] Zinc oxide fume is rich in valuable elements such as lead, zinc, copper, bismuth, and antimony, and can be comprehensively recycled as secondary resources to enhance the utilization value of mineral resources. However, since zinc oxide fume usually contains harmful elements such as arsenic, it has a serious impact on its comprehensive utilization or treatment. Improper disposal and treatment will cause serious harm to ecological safety and human health. However, if these arsenic-containing fumes are directly returned to the lead-zinc smelting process, causing most of the arsenic to circulate in the smelting system, it will lead to a decrease in the metallurgical production efficiency of the main metals and seriously affect the normal operation of the entire smelting process. Therefore, for the sustainable and long-term healthy development of enterprises, to promote the comprehensive recycling of lead-zinc smelting fumes and reduce their harm to the environment and occupation, it is of great significance to carry out arsenic removal treatment on arsenic-containing smelting fume materials and study its arsenic removal technology.

[0005] At present, the main arsenic removal treatment processes for smelting fumes are pyrometallurgical arsenic removal and hydrometallurgical arsenic removal.

[0006] Pyrometallurgical arsenic removal refers to volatilizing arsenic in the form of As 2 O 3 from the fume at high temperature and recovering it by dust collection. The arsenic removal rate of pyrometallurgical arsenic removal is low. During the arsenic removal process, it is easy to have unqualified treatment of fume gas, and gaseous arsenic enters the atmosphere, causing secondary pollution. At the same time, other valuable metals such as zinc and lead in the smelting fume are prone to volatilize into white arsenic (As 2 O 3 ) together with arsenic, resulting in the loss of valuable metals.

[0007] Hydrometallurgical arsenic removal includes acid leaching arsenic removal process and alkali leaching arsenic removal process. Acid leaching arsenic removal mainly uses acidic solutions such as sulfuric acid, nitric acid or waste acid for leaching, and obtains white arsenic through hydrolysis and precipitation. The arsenic remaining in the solution is solidified and stored in the form of iron arsenate precipitate to achieve harmless disposal. The solution after arsenic precipitation is returned to the fume leaching to realize the closed-loop circulation of the acid solution. Alkali leaching arsenic removal mainly uses sodium hydroxide solution or carbonate solution to leach arsenic-containing oxides As 2 O 3 and As 2 O 5 in the fume, converting them into sodium arsenate and entering the solution, thereby achieving effective arsenic removal. The arsenic entering the solution is then precipitated and solidified and stored in the form of precipitates such as iron arsenate to achieve harmless disposal. Hydrometallurgical arsenic removal usually has disadvantages such as long process, high cost, and secondary pollution. Summary of the Invention

[0008] In order to overcome the problems existing in the background technology, the present invention provides a method for removing arsenic from zinc oxide fume, using a process route of leaching zinc oxide fume with sodium hydroxide solution and recycling the leaching solution, which can achieve multiple cycle arsenic removal, realize the goals of circular economy, energy conservation and emission reduction, and has a simple process and a high arsenic removal rate.

[0009] To achieve the above object, the present invention is realized through the following technical solutions:

[0010] The method for arsenic removal from zinc oxide fume includes the following steps:

[0011] (1) Add the zinc oxide fume raw material to the sodium hydroxide solution for leaching according to a liquid-solid ratio V / W of 3:1 to 6:1, while maintaining the temperature at 50°C to 90°C, the stirring speed at 300 to 500 rpm, stir and react for 1.0 to 2.5 h, filter and separate, and wash to obtain solid materials, arsenic-removed leaching solution and washing solution;

[0012] (2) Mix the arsenic-removed leaching solution and the washing solution obtained in step (1) evenly. According to the arsenic content in the mixed solution, add barium salt compound according to a molar ratio of AsO3 3- ∶Ba 2+ of 1∶1.5 to 1.7, maintain the temperature at 50 to 90°C, the stirring speed at 200 to 500 rpm, stir and react for 0.5 to 2.0 h, and then filter and separate to obtain the arsenic-removed solution;

[0013] (3) Introduce CO 2 gas into the arsenic-removed solution obtained in step (2) at room temperature to carbonize and remove lead and zinc, control the pH at the reaction end point to 7.5 to 10, and after reaching the control end point pH, filter and separate to obtain the purified solution;

[0014] (4) Under the conditions of room temperature and a stirring speed of 300 to 500 rpm for the purified solution obtained in step (3), according to the measured bicarbonate and carbonate contents in the solution, add calcium hydroxide at 90% to 105% of the theoretical dosage, stir and react for 0.5 to 2.0 h, filter and separate to obtain the treated solution and solid filter cake, and the solid filter cake is washed and dried to obtain light calcium carbonate;

[0015] (5) Add sodium hydroxide to the treated solution obtained in step (4) to obtain a circulating solution containing NaOH, and return it to step (1) for use in the leaching process of zinc oxide fume.

[0016] Preferably, the mass concentration of the sodium hydroxide solution in step (1) is 10% to 25%.

[0017] Preferably, the zinc oxide fume treated in step (1) contains 0.2% to 10% As, 5% to 20% Pb, 30% to 65% Zn, 0.2% to 1.5% Cd, 0.5% to 2.0% Fe, and SiO 2 0.5% to 2.0%.

[0018] Preferably, the barium salt compound in step (2) is barium hydroxide, barium sulfide, or barium oxide.

[0019] Advantages of the present invention:

[0020] 1. The present invention adopts a method for removing arsenic by leaching zinc oxide fume with an alkaline solution and recycling the leaching solution after recovering valuable metals such as lead, zinc, and calcium, providing a more effective new process for arsenic removal from zinc oxide fume.

[0021] 2. The process equipment of the present invention is simple, and the operation is easy, safe.

[0022] 3. The present invention adopts a method for removing arsenic by leaching with an alkaline solution and recycling the leaching solution, which can realize the comprehensive utilization of resources, reduce environmental pollution, and make full and reasonable use of resources. Specific embodiments

[0023] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings for the convenience of those skilled in the art to understand.

[0024] The main components of the zinc oxide fume raw material used in the embodiments of the present invention are shown in Table 1.

[0025] Table 1 Main components of zinc oxide fume raw material

[0026] Index Pb Zn Cd As Fe <![CDATA[SiO 2 > F Cl Content (%) 12.15 60.26 0.42 0.46 1.09 1.32 0.034 0.032

[0027] Example 1

[0028] (1) Add a certain amount of sodium hydroxide solution with a mass concentration of 25% to the reactor, add the zinc oxide fume raw material according to the liquid-solid ratio (V / W) of 3:1, and carry out a stirring leaching reaction for 1.5 h at a temperature of 50 °C and a stirring speed of 400 rpm, and then filter and separate to obtain solid materials and arsenic-removing leaching solution; the solid materials are washed and dried to obtain arsenic-removed zinc oxide fume; after analysis: the residue rate of the arsenic-removed zinc oxide fume (dry basis) is 82%, the arsenic content in the residue is 0.052%, and the arsenic removal rate is 91%;

[0029] (2) Add the arsenic-removing leaching solution and washing solution obtained in step (1) to the reactor, mix them evenly, and according to the arsenic content in the mixed solution, add barium hydroxide according to the molar ratio of AsO 3 3- ∶Ba 2+ of 1:1.5, and carry out a stirring reaction for 1.0 h at a temperature of 90 °C and a stirring speed of 300 rpm, and then filter and separate to obtain an arsenic-removed solution; after analysis: the arsenic content in the filtrate drops to 0.0027 g / L, and the arsenic removal rate is 99.82%;

[0030] (3) Place the arsenic-removed solution obtained in step (2) into the reactor, and pass CO at room temperature 2The gas is used for carbonizing and removing lead and zinc, and the pH at the reaction end point is controlled at 8. After reaching the controlled end-point pH, filtration and separation are carried out to obtain a purified solution. Through analysis: the lead recovery rate in the solution is 99.93%, and the zinc recovery rate is 99.88%.

[0031] (4) For the purified solution obtained in step (3), under the conditions of room temperature and a stirring speed of 500 rpm, according to the contents of bicarbonate and carbonate in the solution, 90% of the theoretical dosage of powdered calcium hydroxide [Ca(OH) 2 is added to precipitate bicarbonate and carbonate. Stir and react for 1.5 h, then filter and separate to obtain a treated solution and a solid filter cake. The solid filter cake is washed and dried to obtain light calcium carbonate. Through analysis, the CaCO 4 content in the light calcium carbonate product is 98.45%, and the appearance is white.

[0032] (5) Sodium hydroxide is added to the treated solution obtained in step (4) to obtain a circulating solution containing NaOH, which is returned to step (1) for use in the leaching process of zinc oxide fume.

[0033] Example 2

[0034] (1) A certain amount of sodium hydroxide solution with a mass concentration of 10% is added to the reactor. According to the liquid-solid ratio (V / W) of 6:1, zinc oxide fume raw material is added. Under the conditions of a temperature of 90 °C and a stirring speed of 500 rpm, stirring and leaching reaction is carried out for 1.0 h, and then filtration and separation are carried out to obtain solid materials and an arsenic-removed leaching solution; the solid materials are washed and dried to obtain arsenic-removed zinc oxide fume. Through analysis: the residue rate of the arsenic-removed zinc oxide fume (dry basis) is 80%, the arsenic content in the residue is 0.070%, and the arsenic removal rate is 88%.

[0035] (2) The arsenic-removed leaching solution and the washing solution obtained in step (1) are added to the reactor and mixed evenly. According to the arsenic content in the mixed solution, according to the molar ratio of AsO 3 3- ∶Ba 2+ of 1∶1.7, barium sulfide is added. Under the conditions of a temperature of 50 °C and a stirring speed of 500 rpm, after stirring and reacting for 0.5 h, filtration and separation are carried out to obtain an arsenic-removed solution. Through analysis: the arsenic content in the filtrate drops to 0.0017 g / L, and the arsenic removal rate is 99.89%.

[0036] (3) The arsenic-removed solution obtained in step (2) is placed in the reactor, and CO 2 gas is introduced at room temperature for carbonizing and removing lead and zinc. The pH at the reaction end point is controlled at 7.5. After reaching the controlled end-point pH, filtration and separation are carried out to obtain a purified solution. Through analysis: the lead recovery rate in the solution is 99.25%, and the zinc recovery rate is 99.81%.

[0037] (4) The purified solution obtained in step (3), at room temperature and a stirring speed of 300 rpm, according to the bicarbonate and carbonate contents in the solution, is added with powdered calcium hydroxide [Ca(OH) 2 to precipitate bicarbonate and carbonate, stirred and reacted for 0.5 h, filtered and separated to obtain a treated solution and a solid filter cake. The solid filter cake is washed and dried to obtain light calcium carbonate; after analysis, the CaCO 4 content of the light calcium carbonate product is 98.72%, and the appearance is white.

[0038] (5) Sodium hydroxide is added to the treated solution obtained in step (4) to obtain a circulating solution containing NaOH, which is returned to step (1) for the leaching process of zinc oxide fume.

[0039] Example 3

[0040] (1) A certain amount of sodium hydroxide solution with a mass concentration of 15% prepared from the treated solution obtained in step 4 of Example 2 is added to the reactor. According to the liquid-solid ratio (V / W) of 5:1, zinc oxide fume raw material is added, and the leaching reaction is stirred at a temperature of 90 °C and a stirring speed of 300 rpm for 2.5 h. After filtration and separation, solid materials and arsenic-removed leaching solution are obtained; the solid materials are washed and dried to obtain arsenic-removed zinc oxide fume; after analysis: the residue rate of the arsenic-removed zinc oxide fume (dry basis) is 82%, the arsenic content in the residue is 0.038%, and the arsenic removal rate is 93%;

[0041] (2) The arsenic-removed leaching solution and washing solution obtained in step (1) are added to the reactor and mixed evenly. According to the arsenic content in the mixed solution, according to the molar ratio of AsO 3 3- ∶Ba 2+ of 1∶1.6, barium hydroxide is added. At a temperature of 80 °C and a stirring speed of 200 rpm, after stirring and reacting for 2.0 h, filtration and separation are carried out to obtain an arsenic-removed solution; after analysis: the arsenic content in the filtrate drops to 0.0016 g / L, and the arsenic removal rate is 99.88%;

[0042] (3) The arsenic-removed solution obtained in step (2) is placed in the reactor, and CO 2 gas is introduced at room temperature to carbonize and remove lead and zinc, and the pH at the end point of the reaction is controlled at 9. After reaching the controlled end point pH, filtration and separation are carried out to obtain a purified solution; after analysis: the lead recovery rate in the solution is 99.19%, and the zinc recovery rate is 98.99%;

[0043] (4) The purified solution obtained in step (3), at room temperature and a stirring speed of 400 rpm, according to the bicarbonate and carbonate contents in the solution, is added with powdered calcium hydroxide [Ca(OH) 2Precipitate bicarbonate and carbonate ions, stir and react for 2.0 h, filter and separate to obtain a treated solution and a solid cake. The solid cake is washed and dried to obtain light calcium carbonate. Analysis shows that the CaCO content of the light calcium carbonate product is 98.54%, and the appearance is white. 4 The content is 98.54%, and the appearance is white.

[0044] (5) Supplement sodium hydroxide to the treated solution obtained in step (4) to obtain a circulating solution containing NaOH, and return it to step (1) for use in the leaching process of zinc oxide fume.

[0045] Example 4

[0046] (1) Add a certain amount of sodium hydroxide solution with a mass concentration of 20% prepared from the treated solution obtained in step 4 of Example 3 to the reactor. According to the liquid-solid ratio (V / W) of 4:1, add zinc oxide fume raw material, and stir and leach at a temperature of 80 °C and a stirring speed of 400 rpm for 2.0 h. Filter and separate to obtain solid materials and an arsenic-removed leaching solution. The solid materials are washed and dried to obtain arsenic-removed zinc oxide fume. Analysis shows that the residue rate of the arsenic-removed zinc oxide fume (dry basis) is 81%, the arsenic content in the residue is 0.045%, and the arsenic removal rate is 92%.

[0047] (2) Add the arsenic-removed leaching solution and washing solution obtained in step (1) to the reactor, mix evenly, and according to the arsenic content in the mixed solution, add barium oxide in a molar ratio of AsO∶Ba of 1∶1.65. Stir and react at a temperature of 60 °C and a stirring speed of 400 rpm for 1.5 h, then filter and separate to obtain an arsenic-removed solution. Analysis shows that the arsenic content in the filtrate drops to 0.0023 g / L, and the arsenic removal rate is 99.83%. 3 3- ∶Ba 2+ The molar ratio is 1∶1.65, add barium oxide, stir and react at a temperature of 60 °C and a stirring speed of 400 rpm for 1.5 h, then filter and separate to obtain an arsenic-removed solution. Analysis shows that the arsenic content in the filtrate drops to 0.0023 g / L, and the arsenic removal rate is 99.83%.

[0048] (3) Place the arsenic-removed solution obtained in step (2) into the reactor, and pass CO gas at room temperature to carbonize and remove lead and zinc. Control the pH at the end point of the reaction to 10. After reaching the control end point pH, filter and separate to obtain a purified solution. Analysis shows that the lead recovery rate in the solution is 97.26%, and the zinc recovery rate is 95.85%. 2 The gas is carbonized to remove lead and zinc, control the end-point pH to 10, and after reaching the control end-point pH, filter and separate to obtain a purified solution. Analysis shows that the lead recovery rate in the solution is 97.26%, and the zinc recovery rate is 95.85%.

[0049] (4) For the purified solution obtained in step (3), at room temperature and a stirring speed of 350 rpm, according to the content of bicarbonate and carbonate ions in the solution, add powdered calcium hydroxide [Ca(OH) at 950% of the theoretical dosage to precipitate bicarbonate and carbonate ions, stir and react for 1.0 h, filter and separate to obtain a treated solution and a solid cake. The solid cake is washed and dried to obtain light calcium carbonate. Analysis shows that the CaCO content of the light calcium carbonate product is 98.82%, and the appearance is white. 2 Precipitate bicarbonate and carbonate ions, stir and react for 1.0 h, filter and separate to obtain a treated solution and a solid cake. The solid cake is washed and dried to obtain light calcium carbonate. Analysis shows that the CaCO content of the light calcium carbonate product is 98.82%, and the appearance is white. 4 The content is 98.82%, and the appearance is white.

[0050] (5) Sodium hydroxide is added to the treatment solution obtained in step (4) to obtain a circulating solution containing NaOH, which is returned to step (1) for the leaching process of zinc oxide soot.

[0051] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in terms of form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for arsenic removal from zinc oxide fume, characterized in that: it includes the following steps: (1) Add the zinc oxide fume raw material to the sodium hydroxide solution for leaching according to the liquid-solid ratio V / W of 3:1 to 6:1, while maintaining the temperature at 50°C to 90°C, the stirring speed at 300 to 500 rpm, stir and react for 1.0 to 2.5 h, filter and separate, wash to obtain solid materials, arsenic-removing leaching solution and washing solution; (2) Mix the arsenic-removed leaching solution and the washing solution obtained in step (1) evenly. According to the arsenic content in the mixed solution, add barium hydroxide, barium sulfide or barium oxide in a ratio of AsO 3 3- ∶Ba 2+ with a molar ratio of 1∶1.5 - 1.7, maintain the temperature at 50 - 90 °C and the stirring speed at 200 - 500 rpm. After stirring and reacting for 0.5 - 2.0 h, filter and separate to obtain the arsenic-removed solution; (3) Introduce CO into the arsenic-removed solution obtained in step (2) at room temperature 2 to carry out carbonization for removing lead and zinc, control the pH at the reaction end point to be 7.5 - 10. After reaching the end-point pH, perform filtration and separation to obtain a purified solution; (4) Under the conditions of room temperature and a stirring speed of 300 to 500 rpm, for the purified solution obtained in step (3), according to the measured bicarbonate and carbonate contents in the solution, add calcium hydroxide at 90% to 105% of the theoretical dosage, stir and react for 0.5 to 2.0 h, filter and separate to obtain a treated solution and a solid filter cake, and the solid filter cake is washed and dried to obtain light calcium carbonate; (5) Add sodium hydroxide to the treated solution obtained in step (4) to obtain a circulating solution containing NaOH, and return it to step (1) for use in the leaching process of zinc oxide fume.

2. The method for arsenic removal from zinc oxide fume according to claim 1, characterized in that: the mass concentration of the sodium hydroxide solution in step (1) is 10% to 25%.

3. The method for arsenic removal from zinc oxide fume according to claim 1, characterized in that: The zinc oxide fume treated in step (1) contains 0.2 - 10% As, 5 - 20% Pb, 30 - 65% Zn, 0.2 - 1.5% Cd, 0.5 - 2.0% Fe, and 0.5 - 2.0% SiO 2 0.5 - 2.0%.