A method for photooxidative treatment of arsenic sulfide residues

Abstract

This invention provides a method for photo-oxidative treatment of arsenic sulfide slag, comprising the following steps: adding water to the arsenic sulfide slag to adjust the initial arsenic sulfide mass concentration to 2%-20%, adjusting the initial pH to 3-6, adding 2-10% carbon disulfide extractant, controlling the light source to illuminate from the side, and simultaneously stirring and aerating to carry out photo-oxidative leaching; after leaching, separating the organic phase and aqueous phase, cooling the organic phase to precipitate elemental sulfur, stabilizing the filtrate by adding iron and calcium salts, returning the stabilized pressurized filtrate to the photo-oxidative leaching system, and ensuring the filter residue meets the landfill standards for flexible landfills. This method is simple, requires no added chemicals or additional catalysts for oxidation, and directly utilizes the ubiquitous visible light oxidation in nature to achieve safe landfill disposal of high-arsenic slag, resulting in low disposal costs. Furthermore, the photo-oxidation product directly yields elemental sulfur in the solid phase, achieving resource recycling of sulfur.

Description

Technical Field

[0001] This invention relates to the treatment of arsenic sulfide slag, specifically to a method for leaching arsenic sulfide using photo-oxidation technology. Background Technology

[0002] Arsenic pollution primarily originates from mining, mineral processing, and non-ferrous metallurgy industries. Non-ferrous metallurgy, sulfuric acid production, and mineral processing generate highly acidic wastewater containing high concentrations of arsenic and other heavy metals, such as sludge (5%-20% H2SO4). Improper treatment of this wastewater can cause severe environmental pollution. Treatment methods for arsenic-containing acidic wastewater mainly include chemical precipitation, adsorption, reverse osmosis, biological methods, ion exchange, and membrane filtration. In industrial applications, methods such as lime neutralization, sulfide precipitation, iron salt methods, and calcium salt methods are commonly used. Sulfide precipitation is currently widely used for treating this type of arsenic-containing acidic wastewater due to its rapid reaction rate and excellent dehydration properties. However, sulfide precipitation produces large amounts of arsenic sulfide sludge, which is generally yellow and, after drying, becomes powdery slag particles characterized by small particle size, high water content, high arsenic content, high acidity, strong corrosiveness, and high toxicity. Arsenic sulfide slag is a product of the sulfidation and precipitation of high-acid smelting wastewater generated in the copper, lead and zinc smelting industries. Arsenic sulfide slag has become one of the most important solid wastes containing arsenic.

[0003] The treatment methods for arsenic sulfide slag mainly fall into two categories: safe disposal after stabilization and resource utilization, primarily through pyrometallurgical and hydrometallurgical processes. Pyrometallurgical processes utilize the high volatility of arsenic compounds through oxidative roasting, reduction roasting, and smelting to separate and recover arsenic as white arsenic (As₂O₃), achieving resource utilization. However, pyrometallurgical production environments are harsh, causing severe environmental pollution and secondary pollution, resulting in low product purity, which does not comply with environmental policies and principles. Hydrometallurgical processes generally involve two stages: selective leaching of arsenic followed by safe disposal or resource utilization after stabilization. Currently, some hydrometallurgical processes for treating arsenic sulfide exist both domestically and internationally. Bai Meng et al. used sodium hydroxide solution to leach arsenic sulfide slag, achieving an arsenic leaching rate of 95.90% and highly enriching copper and bismuth in the slag. However, this process results in incomplete leaching, limited use of sodium arsenate, and high consumption and price of sodium hydroxide. Sumitomo Corporation of Japan uses copper oxide powder and copper sulfate to replace arsenic sulfide. After solid-liquid separation, the residue containing arsenic acid is slurried, oxidized by air, filtered, and then the arsenic in the filtrate is reduced with SO2 to obtain As2O3. Although researchers have recently discovered the potential applications of arsenic in the electronics and superconducting heat fields, and its future application value may exist, the current market demand for arsenic is relatively small, and there is still a long way to go before industrialization and marketization. The resource utilization of arsenic remains very limited, and safe disposal remains the mainstream demand of the country and the market. According to the "HJ1090-2020 Technical Specification for Arsenic Slag Stabilization and Disposal Engineering", the stabilized arsenic slag must be safely disposed of in landfills. Landfills are classified into rigid landfills and flexible landfills. The "GB 18598-2019 Standard for Pollution Control of Hazardous Waste Landfill" stipulates that arsenic slag with an arsenic content higher than 5% must be placed in rigid landfills. Due to the high disposal costs and limited distribution nationwide, the current mainstream technology involves stabilizing the arsenic sulfide slag to reduce the total arsenic leaching toxicity to 1.2 mg / L before placing it in a flexible landfill. Given the environmental policy restrictions on pyrometallurgical processes, to address the safe disposal of arsenic sulfide slag, it is necessary to first pre-treat it with wet leaching, followed by stabilization with iron salts, calcium salts, and other stabilizers before safe landfilling. Conventional leaching technologies include acid leaching, alkaline leaching, and inorganic salt leaching. These traditional leaching technologies consume large amounts of oxidants, resulting in high processing costs and relatively complex processes. For example, H2O2 itself is a hazardous chemical, easily causing safety accidents and posing significant operational and management challenges. Summary of the Invention

[0004] To address the problems of high cost, large reagent consumption, and easy secondary pollution associated with traditional arsenic sulfide slag treatment technologies, this invention proposes a photo-oxidation method for treating arsenic sulfide slag. This method is simple, requires no added reagents or catalysts for oxidation, and directly utilizes the ubiquitous visible light in nature for oxidation. It has low treatment costs and can directly obtain elemental sulfur.

[0005] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0006] A method for photo-oxidative treatment of arsenic sulfide slag includes the following steps:

[0007] (1) Add water to the arsenic sulfide slag to adjust the initial arsenic sulfide mass concentration to 2%-20%, adjust the initial pH to 3-6 with alkali, add 2%-10% carbon disulfide extractant, control the light source to irradiate the reaction system from the side, and carry out aeration and photo-oxidation leaching while stirring, control the dissolved oxygen to 4-7 mg / L, the leaching temperature to 10℃-42℃, and the light intensity to 835-1190 mW / cm². 2 The light wavelength range is 350-780 nm, the light exposure time is 32-70 hours, and alkali is continuously added during the photo-oxidation process to maintain the pH at 3-6;

[0008] (2) After leaching, the sediment is precipitated and filtered to obtain filter residue I and filtrate I. Filter residue I is unreacted arsenic sulfide. The organic phase and aqueous phase are separated by standing in filtrate I. The aqueous phase is stabilized by adding a mixture of calcium hydroxide and ferric sulfate. After filtration, filter residue II and filtrate II are obtained. The leaching toxicity of filter residue II is less than 1.2 mg / L, which meets the landfill standard of flexible landfill. Filtrate II is returned to the photo-oxidation leaching system. The organic phase is cooled to precipitate elemental sulfur. Cold filtration is used to obtain filter residue III (elemental sulfur) and filtrate III. Filtrate III is carbon disulfide organic phase and is returned to the photo-oxidation reaction.

[0009] Preferably, in step (1), the dissolved oxygen concentration in the water is increased by aeration and light irradiation.

[0010] Preferably, the stirring speed in step (1) is between 20 r / min and 400 r / min. The stirring speed is adjusted in stages. First, stir quickly at 200-400 r / min for 10-20 minutes, then stir slowly at 20-200 r / min for 30-40 minutes, then stir quickly at 200-400 r / min for 10-20 minutes, then stir slowly at 20-200 r / min for 30-40 minutes, and so on.

[0011] Preferably, in step (1), light exposure will increase the reaction temperature, and the leaching temperature is 25-40°C. In the example, the leaching temperature is further preferably 30°C.

[0012] Preferably, the initial arsenic sulfide mass concentration in step (1) is 2%-10%, and in the examples, it is further preferred to have an initial arsenic sulfide mass concentration of 2%.

[0013] Preferably, the arsenic sulfide slag in step (1) has a pH value <2, and its main components are As and S, with a total content of As and S greater than 85%, followed by Cu and Na, with contents of <5% respectively, and the contents of other elements such as Zn, Fe, Pb, Mg and Sb are all below 0.1%.

[0014] Preferably, the arsenic sulfide slag mentioned in step (1) is the product of high acid smelting wastewater generated in the copper, lead and zinc smelting industries after sulfide precipitation.

[0015] Preferably, the amount of carbon disulfide leaching agent added in step (1) is 2% to 10%, and in the examples, the initial mass concentration of arsenic sulfide is 2%.

[0016] Preferably, the cooling precipitation temperature of carbon disulfide filtrate III in step (2) is 0-30 degrees Celsius. In the example, it is further preferred that the cooling precipitation temperature is 10 degrees Celsius.

[0017] Preferably, the calcium hydroxide and ferric sulfate mixture in step (2) is a mixture of calcium hydroxide and ferric sulfate with Ca / Fe = 3-4:1, and the amount added is Ca / As = 3-4:1.

[0018] Preferably, in step (1), alkali is continuously added to maintain the pH at 3-6 during the reaction process. This is because the pH will drop in the first few minutes of the reaction, and hydrogen ions will be generated during the reaction to inhibit the reaction. Therefore, continuously adding alkali to maintain the pH at 3-6 during the reaction process can promote the forward reaction. The alkali is a conventional alkali such as sodium hydroxide.

[0019] In a further preferred embodiment, the initial pH is 6.

[0020] In a further preferred embodiment, the light intensity is 835 mW / cm². 2 .

[0021] In a further preferred embodiment, the initial arsenic sulfide mass concentration was 2%.

[0022] In a further preferred embodiment, the dissolved oxygen during aeration is controlled at 7 mg / L.

[0023] In a further preferred embodiment, the intermittent stirring rates are 20 r / min and 200 r / min, respectively.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] This method is simple, requires no added reagents for oxidation, and does not require additional catalysts for catalytic oxidation. It can directly utilize the ubiquitous visible light in nature for oxidation, resulting in low processing costs and the direct production of elemental sulfur from the solid phase.

[0026] This method uses carbon disulfide to extract and separate the byproduct elemental sulfur while simultaneously conducting a photoreaction. By rapidly stirring during sulfur extraction, the process avoids the elemental sulfur product from being encapsulated by arsenic sulfide, which slows down the photocontamination efficiency. Slow stirring ensures sufficient contact and reaction between light and arsenic sulfide, which greatly improves the photoreaction efficiency. At the same time, high-quality elemental sulfur is obtained through back-extraction.

[0027] 3. The results of the embodiments of the present invention show that light irradiation can significantly improve the leaching effect of arsenic, with the most significant improvement in the visible light region. Temperature, stirring speed, light intensity, and dissolved oxygen are positively correlated with the leaching effect of arsenic. During the reaction process, liquid-phase As exists in the form of As(III). Photoleaching transforms the solid phase into elemental sulfur.

[0028] 4. This invention uses arsenic sulfide slag from a copper smelting industry in Shandong Province as the research object. The arsenic sulfide slag is subjected to photoleaching and stabilization treatment to reduce its leaching toxicity and bring it up to landfill standards. Results show that after 70 hours of visible light irradiation, the arsenic leaching concentration in the arsenic sulfide leachate reaches 3000 mg / L, with a leaching rate of 98%. After precipitation with a mixed reagent of calcium hydroxide and ferric sulfate, the arsenic leaching concentration in the filtrate is only 0.58 mg / L, and the leaching toxicity of the filter residue is significantly reduced to only 1.08 mg / L, meeting the entry standards for flexible landfills.

[0029] The detailed structure of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the experimental setup for Example 1, with light illuminating from the side;

[0031] Figure 2 This is a schematic diagram of the experimental setup for Comparative Example 1, with light shining from the top;

[0032] Figure 3 (a) is a diagram of Comparative Example 1 after being left to stand without illumination for 2 days; Figure 3 (b) is a graph of Comparative Example 1 after 4 hours of visible light exposure and 2 minutes of rest;

[0033] Figure 4 The image shows the results of the photoleaching experiment on industrial arsenic sulfide slag in the inventor's previous research.

[0034] Figure 5 These are SEM images taken after a period of time following the photoreaction treatment of arsenic sulfide in the inventor's earlier research.

[0035] Figure 6These are XRD diffraction patterns of the solid phase at different reaction times during the photoleaching process in the inventor's previous research. As can be seen from the XRD patterns, with the extension of the light irradiation time, the solid phase sample gradually transforms from amorphous arsenic sulfide to crystalline S8, indicating that a new substance, elemental S, is formed as the photoreaction proceeds. The peaks 74-1465 coincide with the peak of elemental sulfur, and the peaks 71-2435 coincide with the peak of arsenic sulfide crystals.

[0036] Figure 7 This is a comparison chart of the effects of visible light and no light on arsenic leaching in the inventor's previous research. Figure 7 Visible light irradiation has a significant effect on the leaching effect of arsenic in arsenic sulfide. Under visible light irradiation, the arsenic leaching concentration gradually increases over time, reaching 403 mg / L after 4 hours, which is 27 times that under no light irradiation.

[0037] 1 is the light source, 2 is the filter, 3 is the oxygen cylinder, 4 is the flow meter, 5 is the circulating water temperature controller, and 6 is the magnetic stirrer. Detailed Implementation Example 1

[0038] The arsenic sulfide slag used in this embodiment was produced by a company in Shandong Province using a flash smelting-flash blowing process to smelt copper. The resulting waste acid was generated using sodium hydrosulfide as a precipitant. The arsenic content in the waste acid was 3-5 g / L.

[0039] The industrial arsenic sulfide slag has a yellow, muddy appearance and a calculated moisture content of 52.7%. According to the solid waste corrosivity identification standard, the pH value of this arsenic sulfide slag is 1.32, which is less than the minimum pH limit of 2 specified in GB 5085.1—2007 "Identification Standard for Hazardous Wastes - Corrosivity Identification Standard", indicating that it is significantly strongly acidic.

[0040] The moisture content, elemental composition and content, corrosivity, and leaching toxicity of industrial arsenic sulfide slag were determined using existing testing methods. The industrial arsenic sulfide slag samples were vacuum dried and digested, and elemental analysis was performed using ICP-OES. The results are shown in Table 1. The main components of this industrial arsenic sulfide slag were As and S, with mass fractions of 35.4% and 50.2%, respectively. The next main components were Cu and Na, accounting for 0.39% and 0.35%, respectively. The contents of other elements such as Zn, Fe, Pb, Mg, and Sb were all below 0.1%.

[0041] Table 1. Elemental content (%) of industrial arsenic sulfide slag

[0042] name As S Cu Zn Fe Pb Mg Na Sb Ca content 35.4 50.2 0.39 0.01 0.023 0.096 0.01 0.35 0.029 0.04

[0043] To test whether the arsenic sulfide slag could be directly placed in a landfill (the standard for entry into a flexible landfill is an As leaching concentration of <1.2 mg / L), the leaching toxicity of the arsenic sulfide slag was tested using the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The results are shown in Table 2. According to GB18598-2019, the Cu, Zn, and Pb elements in the industrial slag all met the standards for landfill entry, while the As leaching concentration of 890.6 mg / L far exceeded the national limit, requiring further treatment and disposal.

[0044] Table 2 Leaching toxicity of industrial arsenic sulfide slag (mg / L)

[0045] element As Cu Zn Pb 890.6 0.19 4.7 0.98 GB18598—2019 ＜1.2 ＜120 ＜120 ＜1.2

[0046] The specific processing method includes the following steps:

[0047] Water was added to the arsenic sulfide slag to adjust the initial arsenic sulfide concentration to 2% and the initial pH to 6. 10% carbon disulfide extractant was added. The reaction system was illuminated from the side by a controlled light source, and aeration and photo-oxidative leaching were carried out simultaneously with stirring. The dissolved oxygen was controlled at 7 mg / L, the leaching temperature at 30℃, and the light intensity at 835 mW / cm². 2 The light wavelength range is 350-780 nm, and the illumination time is 70 hours; the stirring speed in step (1) is 20 r / min-400 r / min, and the stirring speed is adjusted in stages. First, stir at 200 r / min for 20 minutes, then stir at 20 r / min for 30 minutes, then stir at 200 r / min for 20 minutes, then stir at 20 r / min for 30 minutes, and so on. During the reaction process, alkali is continuously added to maintain the pH at 6.

[0048] After leaching, precipitation and filtration are performed to obtain filter residue I and filtrate I. Filter residue I contains unreacted arsenic sulfide. The organic phase and aqueous phase are separated by allowing the filtrate I to stand. The aqueous phase is stabilized by adding a mixed reagent of calcium hydroxide and ferric sulfate, with a mass ratio of Ca / Fe = 3-4:1 and an addition amount of Ca / As = 3-4:1. After filtration, filter residue II and filtrate II are obtained. The leaching toxicity of filter residue II is less than 1.2 mg / L, meeting the landfill standards for flexible landfills. Filtrate II is returned to the photo-oxidative leaching system. The organic phase is cooled to precipitate elemental sulfur at a controlled temperature of 10°C. Cold filtration yields filter residue III containing elemental sulfur, while the organic phase of filtrate III (carbon disulfide) is returned to the photo-oxidative reaction.

[0049] Stabilization and toxicity leaching experiments were conducted on the industrial arsenic sulfide filtrate after photoleaching:

[0050] Take 100 mL of industrial arsenic sulfide slag filtrate after 70 h of light exposure, add calcium hydroxide and ferric sulfate, and after complete precipitation, extract the filter residue and filtrate. Add sulfuric acid / nitric acid solution (pH=3.2) with a mass ratio of 2:1 to the filter residue at a solid-liquid ratio of 10:1 (L / kg), and place it in a horizontal shaker to simulate the safe disposal process of industrial arsenic sulfide slag after photoleaching.

[0051] The results showed that the arsenic leaching concentration of the arsenic sulfide extract reached 3000 mg / L after 70 h of visible light irradiation, with a leaching rate of 98%. The arsenic leaching concentration of the filtrate obtained after precipitation with a mixed reagent of calcium hydroxide and ferric sulfate was only 0.58 mg / L, and the leaching toxicity of the filter residue was significantly reduced to only 1.08 mg / L, which was reduced to the entry standard of flexible landfill. Example 2

[0052] The processing object is the same as in Example 1, and the processing method is as follows:

[0053] (1) Add water to the arsenic sulfide slag to adjust the initial arsenic sulfide mass concentration to 3%, adjust the initial pH to 5, add 3% carbon disulfide extractant, control the light source to illuminate the reaction system from the side, and carry out aeration and photo-oxidation leaching while stirring, control the dissolved oxygen to 6 mg / L, the leaching temperature to 30℃, and the light intensity to 900 mW / cm². 2 The light wavelength range is 350-780 nm, and the illumination time is 70 hours; the stirring speed in step (1) is 20 r / min-400 r / min, and the stirring speed is adjusted in stages. First, stir at 300 r / min for 30 minutes, then stir at 30 r / min for 30 minutes, then stir at 300 r / min for 30 minutes, and then stir at 30 r / min for 30 minutes. This process is repeated in sequence. During the reaction, alkali is continuously added to maintain the pH at 5.

[0054] After leaching, precipitation and filtration are performed to obtain filter residue I and filtrate I. Filter residue I contains unreacted arsenic sulfide. The organic phase and aqueous phase are separated by allowing the filtrate I to stand. The aqueous phase is stabilized by adding a mixed reagent of calcium hydroxide and ferric sulfate, with a mass ratio of Ca / Fe = 3-4:1 and an addition amount of Ca / As = 3-4:1. After filtration, filter residue II and filtrate II are obtained. The leaching toxicity of filter residue II is less than 1.2 mg / L, meeting the landfill standards for flexible landfills. Filtrate II is returned to the photo-oxidative leaching system. The organic phase is cooled to precipitate elemental sulfur at a controlled temperature of 10°C. Cold filtration yields filter residue III containing elemental sulfur, while the organic phase of filtrate III (carbon disulfide) is returned to the photo-oxidative reaction.

[0055] Stabilization and toxicity leaching experiments were conducted on the industrial arsenic sulfide filtrate after photoleaching:

[0056] Take 100 mL of industrial arsenic sulfide slag filtrate after 70 h of light exposure, add calcium hydroxide and ferric sulfate, and after complete precipitation, extract the filter residue and filtrate. Add sulfuric acid / nitric acid solution (pH=3.2) with a mass ratio of 2:1 to the filter residue at a solid-liquid ratio of 10:1 (L / kg), and place it in a horizontal shaker to simulate the safe disposal process of industrial arsenic sulfide slag after photoleaching.

[0057] The results showed that the arsenic leaching concentration of the arsenic sulfide extract reached 2800 mg / L after 70 h of visible light irradiation, with a leaching rate of 96%. The arsenic leaching concentration of the filtrate obtained after precipitation with a mixed reagent of calcium hydroxide and ferric sulfate was only 0.32 mg / L, and the leaching toxicity of the filter residue was significantly reduced to only 0.95 mg / L, which is lower than the entry standard for flexible landfills. Example 3

[0058] The processing object is the same as in Example 1, and the processing method is as follows:

[0059] (1) Water was added to the arsenic sulfide slag to adjust the initial arsenic sulfide mass concentration to 4%, the initial pH to 6, and 5% carbon disulfide extractant was added. The light source was controlled to illuminate the reaction system from the side. Aeration and photo-oxidation leaching were carried out while stirring. The dissolved oxygen was controlled to be 5 mg / L, the leaching temperature was 20℃, and the light intensity was 1190 mW / cm². 2 The light wavelength range is 350-780 nm, and the illumination time is 70 hours; the stirring speed in step (1) is 20 r / min-400 r / min, and the stirring speed is adjusted in stages. First, stir at 200 r / min for 30 minutes, then stir at 20 r / min for 30 minutes, then stir at 200 r / min for 30 minutes, then stir at 20 r / min for 30 minutes, and so on. During the reaction process, alkali is continuously added to maintain the pH at 6.

[0060] After leaching, precipitation and filtration are performed to obtain filter residue I and filtrate I. Filter residue I contains unreacted arsenic sulfide. The organic phase and aqueous phase are separated by allowing the filtrate I to stand. The aqueous phase is stabilized by adding a mixed reagent of calcium hydroxide and ferric sulfate, with a mass ratio of Ca / Fe = 3-4:1 and an addition amount of Ca / As = 3-4:1. After filtration, filter residue II and filtrate II are obtained. The leaching toxicity of filter residue II is less than 1.2 mg / L, meeting the landfill standards for flexible landfills. Filtrate II is returned to the photo-oxidative leaching system. The organic phase is cooled to precipitate elemental sulfur at a controlled temperature of 10°C. Cold filtration yields filter residue III containing elemental sulfur, while the organic phase of filtrate III (carbon disulfide) is returned to the photo-oxidative reaction.

[0061] Stabilization and toxicity leaching experiments were conducted on the industrial arsenic sulfide filtrate after photoleaching:

[0062] Take 100 mL of industrial arsenic sulfide slag filtrate after 32 h of light exposure, add calcium hydroxide and ferric sulfate, and after complete precipitation, extract the filter residue and filtrate. Add sulfuric acid / nitric acid solution (pH=3.2) with a mass ratio of 2:1 to the filter residue at a solid-liquid ratio of 10:1 (L / kg), and place it in a horizontal shaker to simulate the safe disposal process of industrial arsenic sulfide slag after photoleaching.

[0063] The results showed that the arsenic leaching concentration of the arsenic sulfide extract reached 2900 mg / L after 70 h of visible light irradiation, with a leaching rate of 97%. The arsenic leaching concentration of the filtrate obtained after precipitation with a mixed reagent of calcium hydroxide and ferric sulfate was only 0.83 mg / L, and the leaching toxicity of the filter residue was significantly reduced to only 1.17 mg / L, which was reduced to the entry standard of flexible landfill.

[0064] Comparative Example 1

[0065] In actual industrial arsenic sulfide slag photoleaching, the treatment objects and control parameters are the same as in Example 1. Comparison of different light angles, top light and side light, the top extractant affects light absorption. After 48 hours of top light, the arsenic leaching rate of the arsenic sulfide extract is 40%, while after 48 hours of side light, the arsenic leaching rate of the arsenic sulfide extract is 82%.

[0066] Comparative Example 2

[0067] In actual industrial arsenic sulfide slag photoleaching, the treatment objects and control parameters are the same as in Example 1. The separation and photooxidation analysis were compared between the arsenic sulfide slag without extractant and the arsenic sulfide slag with extractant. The arsenic leaching rate of the arsenic sulfide slag without extractant after 48 hours was 48%, while the arsenic sulfide slag with extractant after 48 hours had an arsenic leaching rate of 80%. When cooled to 15 degrees, the purity of the precipitated elemental sulfur reached 92%.

[0068] Comparative Example 3

[0069] In actual industrial arsenic sulfide slag photoleaching, the treatment object and control parameters are the same as in Example 1, but the stirring method is different. The stirring speed is 200 r / min, and non-staged stirring is used. After 70 hours of staged stirring, the arsenic leaching rate of the arsenic sulfide extract is 98%, and after 70 hours of continuous constant stirring speed, the arsenic leaching rate of the arsenic sulfide extract is 78%.

[0070] Comparative Example 4

[0071] In actual industrial arsenic sulfide slag photoleaching, the treatment object and control parameters are the same as in Example 1. The initial pH is 6, but no alkali is continuously added during the reaction process, so the pH will drop and cannot be maintained at around 6, affecting the reaction. After 36 hours of treatment, the arsenic leaching rate of the arsenic sulfide leachate is 40%, while the arsenic leaching rate of the arsenic sulfide leachate maintained at pH 6 by continuous alkali addition is 80%.

[0072] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for photooxidative treatment of arsenic sulfide residues, characterized in that, Includes the following steps: (1) Add water to the arsenic sulfide slag to adjust the initial arsenic sulfide mass concentration to 2%-20%, adjust the initial pH to 3-6 with alkali, add 2%-10% carbon disulfide extractant, control the light source to irradiate the reaction system from the side, and carry out aeration and photo-oxidation leaching while stirring, control the dissolved oxygen to 4-7 mg / L, the leaching temperature to 25℃-40℃, and the light intensity to 835-1190 mW / cm². 2 The light wavelength range is 350-780 nm, and the illumination time is 32-70 hours; the arsenic sulfide slag has a pH value <2, the main components are As and S, the total content of As and S is greater than 85%, followed by Cu and Na, with contents of <5% respectively, and the contents of elements Zn, Fe, Pb, Mg and Sb are all below 0.1%; during step (1) photo-oxidation, alkali is continuously added to maintain the pH at 3-6; (2) After leaching, the sediment is precipitated and filtered to obtain filter residue I and filtrate I. Filter residue I is unreacted arsenic sulfide. The organic phase and the aqueous phase are separated by standing in filtrate I. The aqueous phase is stabilized by adding a mixture of calcium hydroxide and ferric sulfate. After further filtration, filter residue II and filtrate II are obtained. The leaching toxicity of filter residue II is less than 1.2 mg / L, meeting the landfill standard for flexible landfills. Filtrate II is returned to the photo-oxidative leaching system. The organic phase precipitates elemental sulfur through cooling. Cold filtration yields filter residue III (elemental sulfur) and filtrate III. Filtrate III, which is a carbon disulfide organic phase, is returned to the photo-oxidative reaction. The calcium hydroxide and ferric sulfate mixed reagent is a mixture of calcium hydroxide and ferric sulfate with a mass ratio of Ca / Fe = 3-4:1, and the amount added is Ca / As = 3-4:

1.

2. The method of photooxidative treatment of arsenic sulfide residues according to claim 1, characterized by that, In step (1), the stirring speed is adjusted in stages. First, stir quickly at 200-400 r / min for 10-20 minutes, then stir slowly at 20 r / min-30 r / min for 30-40 minutes, then stir quickly at 200-400 r / min for 10-20 minutes, then stir slowly at 20 r / min-30 r / min for 30-40 minutes, and repeat this cycle.

3. The method for photo-oxidative treatment of arsenic sulfide slag according to claim 1 or 2, characterized in that, The initial arsenic sulfide mass concentration mentioned in step (1) is 2%-10%.

4. The method of photooxidative treatment of arsenic sulfide residues according to claim 1 or 2, characterized by that, The arsenic sulfide slag mentioned in step (1) is the product of sulfide precipitation of high-acid smelting wastewater generated in the copper, lead and zinc smelting industries.

5. The method of photooxidative treatment of arsenic sulfide residues according to claim 1 or 2, characterized by that, In step (1), the amount of carbon disulfide extractant added is 2% to 5%.

6. The method of photooxidative treatment of arsenic sulfide residues according to claim 1 or 2, characterized by that, The cooling precipitation temperature is 0-10 degrees Celsius.

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