Enhanced treatment method for acidic arsenic-containing wastewater

Abstract

The invention belongs to the field of arsenic pollution treatment, and particularly relates to an enhanced treatment method for acidic arsenic-containing wastewater. According to the carbonate mineral enhanced crystallization treatment method for the acidic arsenic-containing wastewater, on the basis of the structural compatibility between carbonate minerals and calcium arsenite minerals, the calcium arsenite minerals are induced to be subjected to epitaxial crystallization and mineralization by utilizing the interface action of the carbonate minerals. Compared with the technical method without carbonate mineral induction, the Ca-As (III) product obtained by the technical scheme has better crystallinity, larger crystal size and lower solubility, so that the removal of As (III) in the wastewater can be enhanced.

Description

Technical Field

[0001] The present application relates to the field of arsenic pollution control, and more specifically, to an enhanced treatment method for acidic arsenic-containing wastewater. Background Art

[0002] Acidic arsenic wastewater (AIDW) is a common industrial wastewater in the non-ferrous metal smelting industry. Metallic elements such as copper, lead, and zinc are often associated with sulfur and arsenic. The SO2 flue gas produced during the smelting process is primarily used in industrial acid production, generating large amounts of AIDW. Because arsenic is highly toxic and an internationally recognized carcinogen, AIDW requires proper treatment.

[0003] Chemical precipitation is an effective method for treating arsenic-containing wastewater. It converts soluble arsenic into insoluble arsenic by applying a precipitant, thereby achieving arsenic removal from the wastewater. The valence states of arsenic in acidic arsenic-containing wastewater include As(III) and As(V), with As(III) being the main valence state. Due to differences in molecular structure, As(III) is generally more difficult to remove than As(V). Therefore, the addition of an oxidant is often used to oxidize As(III) to As(V) to achieve effective treatment of As(III) in arsenic-containing wastewater. Patent documents CN117383752A, CN115677072A, etc. all use the auxiliary means of adding a large amount of oxidants to enhance the removal of As(III). The types of oxidants involved include hydrogen peroxide, ozone, calcium hypochlorite, etc. These oxidants usually require a high market price, resulting in high treatment costs for acidic arsenic-containing wastewater. Summary of the Invention

[0004] In response to the defects of the existing technology, the purpose of this application is to provide an enhanced treatment method for acidic arsenic-containing wastewater, aiming to solve the technical problems of the existing technology in removing arsenic from acidic arsenic-containing wastewater, especially trivalent arsenic, which requires the addition of a large amount of oxidant to oxidize all As(III) to As(V), resulting in large amounts of reagents and high treatment costs.

[0005] To achieve the above objectives, in a first aspect, the present application provides a method for enhanced treatment of acidic arsenic-containing wastewater, comprising the following steps: (1) adding an excess amount of carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture so that the hydrogen ions in the arsenic-containing wastewater are neutralized and insoluble carbonate mineral particles remain in the system after the reaction; (2) introducing a calcium-containing compound into the system after the reaction in step (1), wherein the calcium-containing compound is alkaline when in contact with water, so that the calcium ions dissociated from the calcium-containing compound in contact with water react with As(III) and As(V) in the arsenic-containing wastewater to precipitate and crystallize to form insoluble Ca-As(III) minerals and Ca-As(V) minerals, wherein the crystallization of the Ca-As(III) minerals occurs on the surface of the carbonate minerals; after the reaction is completed, the solid and liquid are separated to obtain arsenic-rich slag and arsenic-removed liquid.

[0006] Preferably, in step (1), the amount of carbonate mineral added to the acidic arsenic-containing wastewater is 10-500 g / L; and the stirring reaction time is 12-24 hours.

[0007] Preferably, in step (1), carbonate minerals are added to the acidic arsenic-containing wastewater and stirred to react until the pH of the system is 8-9.

[0008] Preferably, the mass ratio of the insoluble carbonate mineral particles remaining in the system after the reaction in step (1) to the As(III) in the system is 10-30:1.

[0009] Preferably, the acidic arsenic-containing wastewater contains sulfate, and step (1) includes the following sub-steps: (1-1) adding a carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture thoroughly to allow the carbonate mineral to react with a portion of the hydrogen ions in the wastewater to neutralize, and the dissociated calcium ions in the carbonate mineral to react with sulfate ions in the wastewater to form gypsum, and separating the solid and liquid to obtain gypsum slag and pre-neutralized arsenic-containing wastewater; the ratio of the molar amount of the carbonate mineral added in step (1-1) to the molar amount of sulfate ions in the wastewater is 1 to 3:1; and the pH of the system after the neutralization reaction is 1 to 2; (1-2) Further adding carbonate minerals to the pre-neutralized arsenic-containing wastewater in step (1-1) until the amount is excessive, and stirring to neutralize the remaining hydrogen ions in the arsenic-containing wastewater, and insoluble carbonate mineral particles remain in the system after the reaction.

[0010] Preferably, the molar ratio of calcium in the calcium-containing compound added in step (2) to arsenic in the wastewater is Ca / As in the range of 0.5 to 5:1; and the pH of the system after the reaction is completed is in the range of 11.5 to 12.5.

[0011] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies: (1) The present invention provides a carbonate mineral-enhanced crystallization method for treating acidic arsenic-containing wastewater. Based on the structural compatibility between carbonate minerals and calcium arsenite minerals, the interfacial interaction of carbonate minerals is utilized to induce epitaxial crystallization of calcium arsenite minerals. Compared to technical methods without carbonate mineral induction, the Ca-As(III) product obtained by the technical solution of the present invention has better crystallinity, larger crystal size, and lower solubility, thereby enhancing the removal of As(III) from wastewater.

[0012] (2) Compared with the traditional method of enhancing As(III) removal by adding a large amount of oxidants, the carbonate minerals used in the present invention have significant cost advantages. For example, the market price of common oxidants such as hydrogen peroxide and bleaching powder is around 1,000 yuan / ton, while the market price of carbonate minerals such as limestone used in the present invention is only 70-80 yuan / ton, which is much lower than the market price of oxidants. The present invention uses low-cost carbonate minerals to enhance As(III) removal, avoids the use of large amounts of oxidants, and can effectively reduce treatment costs.

[0013] (3) The carbonate mineral enhanced crystallization treatment method for acidic arsenic-containing wastewater proposed in the present invention can reduce As(III) to 0.8 ppm and As(V) to 0.2 ppm at a very low cost, providing convenience for the subsequent deep arsenic removal of wastewater. In addition, the Ca-As(III) crystalline minerals induced by the carbonate mineral interface of the present invention have better long-term stability than the Ca-As(III) weak crystalline products generated by direct arsenic precipitation using calcium hydroxide in the prior art, and are more resistant to the decomposition of carbon dioxide in the environment. Therefore, they are more conducive to the temporary storage and safe landfill of the obtained arsenic-rich slag.

[0014] (4) The carbonate minerals used in the present invention have multiple functions such as enhancing As(III) removal, neutralizing wastewater acidity, and promoting gypsum formation, thereby achieving efficient utilization of carbonate minerals.

[0015] (5) The materials used in the present invention are simple, and only carbonate minerals and calcium-containing compounds are used, which can improve the operability and convenience of the treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic flow chart of an enhanced treatment method for acidic arsenic-containing wastewater provided in Example 1 of the present application; Figure 2 This is a scanning electron microscope image of calcite and its surface epitaxially crystallized calcium arsenite mineral before and after the reaction in Example 1 of the present application; Figure 3 is a scanning electron microscope image of calcium arsenate minerals scattered on the surface of calcite in Example 1 of the present application; Figure 4This is a schematic flow chart of an enhanced treatment method for acidic arsenic-containing wastewater provided in Example 3 of the present application; Figure 5 This is a scanning electron microscope image of the calcium arsenic precipitate obtained by directly reacting calcium hydroxide with arsenic-containing wastewater in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0018] The present invention provides an enhanced treatment method for acidic arsenic-containing wastewater, comprising the following steps: (1) adding an excess amount of carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture so that the hydrogen ions in the arsenic-containing wastewater are neutralized and insoluble carbonate mineral particles remain in the system after the reaction; (2) introducing a calcium-containing compound into the system after the reaction in step (1), wherein the calcium-containing compound is alkaline when in contact with water, so that the calcium ions dissociated by the calcium-containing compound in contact with water react with As(III) and As(V) in the arsenic-containing wastewater to precipitate and crystallize to form insoluble Ca-As(III) minerals and Ca-As(V) minerals, wherein the crystallization of the Ca-As(III) mineral occurs on the surface of the carbonate mineral; after the reaction is completed, the solid and liquid are separated to obtain arsenic-rich slag and arsenic-removed liquid. The arsenic-rich slag is safely landfilled, and the arsenic-removed liquid is used for production reuse.

[0019] The treatment method of the present invention is applicable to acidic arsenic-containing wastewater generated in various scenarios. In some embodiments, the acidic arsenic-containing wastewater has a pH less than 2, a total arsenic concentration of 10 to 15,000 mg / L, and the molar proportion of As(III) in the total arsenic is not less than 20%. In other embodiments, the acidic arsenic-containing wastewater has a pH less than 1, a total arsenic concentration of 1,000 to 10,000 mg / L, and the molar proportion of As(III) in the total arsenic is not less than 50%.

[0020] In some embodiments, in step (1), the amount of carbonate mineral added to the acidic arsenic-containing wastewater is 10-500 g / L, preferably 10-300 g / L; and the stirring reaction time is 12-24 hours.

[0021] In some embodiments, in step (1), carbonate minerals are added to the acidic arsenic-containing wastewater and stirred to react until the pH of the system is 8-9.

[0022] In some embodiments, the mass ratio of the insoluble carbonate mineral particles remaining in the system after the reaction in step (1) to the As(III) in the system is 10-30:1.

[0023] In other embodiments, for the case where the acidic arsenic-containing wastewater contains sulfate, step (1) may include the following sub-steps: (1-1) adding a carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture thoroughly to allow the carbonate mineral to react with a portion of the hydrogen ions in the wastewater to neutralize, and the dissociated calcium ions in the carbonate mineral to react with sulfate ions in the wastewater to form gypsum, and separating the solid and liquid to obtain gypsum slag and pre-neutralized arsenic-containing wastewater; the ratio of the molar amount of the carbonate mineral added in step (1-1) to the molar amount of sulfate ions in the wastewater is 1 to 3:1; and the pH of the system after the neutralization reaction is 1 to 2; (1-2) Further adding carbonate minerals to the pre-neutralized arsenic-containing wastewater in step (1-1) until the amount is excessive, and stirring to neutralize the remaining hydrogen ions in the arsenic-containing wastewater, and insoluble carbonate mineral particles remain in the system after the reaction.

[0024] The main component of the carbonate mineral of the present invention is calcium carbonate. The carbonate mineral in step (1) includes, but is not limited to, one or more of calcite, dolomite, limestone, limestone, and marble. The calcium-containing compound in step (2) of the present invention includes, but is not limited to, one or more of calcium oxide, calcium hydroxide, quicklime, slaked lime, and lime milk.

[0025] In some embodiments, the molar ratio of calcium in the calcium-containing compound added in step (2) to arsenic in the wastewater is Ca / As in a range of 0.5-5:1, preferably 0.5-2:1; and the pH of the system after the reaction is completed is 11.5-12.5.

[0026] Prior art carries out arsenic removal treatment to acidic arsenic-containing wastewater by directly adding calcium oxide or calcium hydroxide, and main principle is to utilize the direct precipitation reaction between calcium ion and arsenic ion, realizes the reduction of arsenic concentration in wastewater, but due to the lack of process regulation to calcium arsenic precipitation reaction, can only obtain precipitate product with poor crystallinity, smaller size, higher solubility, and the Ca-As (III) weak crystalline product long-term stability of direct arsenic precipitation generation using calcium hydroxide is not good, can not resist the decomposition of carbon dioxide in environment well. The present invention, by adding carbonate minerals, utilizes the structural compatibility between carbonate minerals and calcium arsenite minerals, uses carbonate mineral interface as substrate to regulate calcium arsenic precipitation crystallization process, promotes the crystallinity and crystal size of calcium arsenic precipitation product and reduces its solubility, can reduce As (III) concentration to 0.8 mg / L, and significantly improves its long-term stability. In the field of arsenic-containing wastewater treatment, it may not be difficult to reduce arsenic concentration from thousands of mg / L to several mg / L, but, it is very difficult to realize the further depth reduction of arsenic concentration, such as every reduction of 0.1 mg / L. Through the technical solution of the present invention, the traditional method is improved by using cheap and readily available carbonate minerals, so that the As(III) concentration can be further reduced by nearly 30%, achieving unexpected technological progress.

[0027] The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally based on conventional conditions.

[0028] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0029] The process parameters in the following examples where no specific conditions are specified are generally based on conventional conditions.

[0030] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0031] Example 1 The pH of the acidic arsenic-containing wastewater was 1.3, and the total arsenic concentration was 1150 mg / L, of which the As(III) concentration was 1130 mg / L and the As(V) concentration was 20 mg / L.

[0032] This embodiment uses the acidic arsenic-containing wastewater to Figure 1 The steps shown are handled as follows: (1) Adding 20 g / L of calcite to the acidic arsenic-containing wastewater, stirring continuously, and reacting for 12 hours; the pH of the suspension after the reaction is 8.5, in which excess calcite particles are visible, and the mass ratio of excess calcite particles to As(III) is 15:1; (2) Add 1 g / L calcium hydroxide to the system after the reaction in step (1), continue stirring, and react for 24 hours; the pH of the suspension after the reaction is 12.3; (3) Separating the suspension after the reaction in step (2) from solid to liquid to obtain arsenic-rich slag and arsenic-removed liquid.

[0033] After testing, the remaining As(III) concentration in the arsenic-removed liquid was 0.83 mg / L, and the As(V) concentration was 0.24 mg / L. The As(III) removal rate was 99.93%, and the As(V) removal rate was 98.80%.

[0034] The arsenic-rich slag obtained in step (3) was subjected to scanning electron microscopy analysis. Figure 2 As shown in Figures (a), (b), and (c), (a) is a scanning electron micrograph of calcite before the reaction, (b) is a scanning electron micrograph of the arsenic-rich slag after the reaction, and (c) is a partial magnification of (b). It can be observed that after the reaction, a large number of well-crystallized calcium arsenite plate-like crystals are formed on the surface of the calcite mineral. These crystals are arranged in an orderly manner on the surface of the calcite mineral in a vertical growth manner, with crystal sizes ranging from 0.3 to 0.8 microns horizontally and 0.9 to 1.3 microns vertically. The calcite {104} surface originally had a smooth cleavage plane, indicating that the presence of calcite during the reaction controlled the crystallization process of the calcium arsenite mineral, inducing the formation of large-sized, highly crystalline, and low-solubility products, playing an important role in enhancing the deep removal of arsenic.

[0035] At the same time, the following was also observed in the arsenic-rich slag after the reaction: Figure 3 As shown in the SEM morphology of calcium arsenate, it can be seen that compared with calcium arsenite, calcium arsenate does not have a strong interaction with the surface of calcite minerals, so it is speculated that the crystallization of Ca-As(V) minerals occurs in the solution rather than on the surface of the calcite minerals. Compared with Comparative Example 3, which directly uses calcium hydroxide to remove arsenic, the residual As(III) concentration in the arsenic-removed liquid obtained after treatment in this example is 0.83 mg / L and the As(V) concentration is 0.24 mg / L, while the residual As(III) concentration in the water after treatment in Comparative Example 3 is 1.14 mg / L and the As(V) concentration is 0.23 mg / L. The As(V) concentrations are comparable, which also indicates that the crystallization and removal of As(V) mainly occurs in the solution, while the introduction of carbonate minerals significantly promotes the removal of As(III), and also indicates that calcium arsenite does have a strong interaction with the surface of the calcite minerals.

[0036] The obtained arsenic-rich slag was subjected to a leaching toxicity test in accordance with the "Hazardous Waste Identification Standard - Leaching Toxicity Identification (GB5085.3-2007)", and the arsenic leaching concentration was 1.22 mg / L, which is lower than the standard limit of 5 mg / L. The arsenic-rich slag was subjected to a leaching toxicity test after being stored for 3 months, and the arsenic leaching concentration was 1.31 mg / L, which is still lower than the standard limit. This shows that the arsenic-rich slag obtained by the present invention can be stably stored for a long time.

[0037] Example 2 The pH of the acidic arsenic-containing wastewater was 0.8, and the total arsenic concentration was 11380 mg / L, of which the As(III) concentration was 7660 mg / L and the As(V) concentration was 3720 mg / L.

[0038] This embodiment uses the acidic arsenic-containing wastewater to Figure 1 The steps shown are handled as follows: (1) 210 g / L limestone was added to the acidic arsenic-containing wastewater, and the mixture was stirred continuously for 12 hours. The pH of the suspension after the reaction was 8.6, and excess limestone particles were visible. The mass ratio of excess limestone particles to As(III) was 20:1. (2) Add 13 g / L of calcium oxide to the system after the reaction in step (1), continue stirring, and react for 24 hours; the pH of the suspension after the reaction is 12.2; (3) Separating the suspension after the reaction in step (2) from solid to liquid to obtain arsenic-rich slag and arsenic-removed liquid.

[0039] After testing, the remaining As(III) concentration in the arsenic-removed liquid was 0.82 mg / L, and the As(V) concentration was 0.25 mg / L. The As(III) removal rate was 99.989%, and the As(V) removal rate was 99.993%.

[0040] Example 3 The pH of the acidic arsenic-containing wastewater was 0.5, the sulfate concentration was 9800 mg / L, the total arsenic concentration was 6510 mg / L, of which the As(III) concentration was 5240 mg / L and the As(V) concentration was 1270 mg / L.

[0041] This embodiment uses the acidic arsenic-containing wastewater to Figure 4 The steps shown are handled as follows: (1) Add 14 g / L of calcite to the acidic arsenic-containing wastewater, continue stirring, and react for 12 hours; the pH of the suspension after the reaction is 1.5; (2) separating the suspension after the reaction in step (1) from the solid-liquid phase to obtain gypsum slag and arsenic-containing liquid; (3) adding 95 g / L of calcite to the arsenic-containing solution obtained in step (2), stirring continuously, and reacting for 12 hours; the pH of the suspension after the reaction is 8.4, and the mass ratio of excess calcite particles to As(III) is 18:1; (4) Add 9 g / L of calcium hydroxide to the system after the reaction in step (3), continue stirring, and react for 24 hours; the pH of the suspension after the reaction is 12.3; (5) Separating the suspension after the reaction in step (4) from solid to liquid to obtain arsenic-rich slag and arsenic-removed liquid.

[0042] After testing, the remaining As(III) concentration in the arsenic-removed liquid obtained in step (5) was 0.84 mg / L, and the As(V) concentration was 0.23 mg / L. The As(III) removal rate was 99.984%, and the As(V) removal rate was 99.982%.

[0043] Comparative Example 1 The other steps were the same as those in Example 1, except that the carbonate mineral added in step (1) was not excessive, i.e., the amount of calcite added was 2 g / L. The pH of the suspension after the reaction in step (1) was 2.1, and no calcite particles remained. The pH of the suspension after the reaction in step (2) was 11.9. The residual As(III) concentration in the arsenic-removed solution obtained in step (3) was 3.47 mg / L, and the As(V) concentration was 1.15 mg / L. The treatment effects of As(III) and As(V) were significantly lower than those in Example 1.

[0044] Comparative Example 2 The other steps were the same as those in Example 1, except that the carbonate mineral added in step (1) was excessive but insufficient, i.e., the amount of calcite added was only 10 g / L. The pH of the suspension after the reaction in step (1) was 8.4, in which excessive calcite particles were visible, and the mass ratio of the excessive calcite particles to As(III) was 6:1. The pH of the suspension after the reaction in step (2) was 12.3. The concentration of the remaining As(III) in the arsenic-removed solution obtained in step (3) was 0.96 mg / L, and the concentration of As(V) was 0.24 mg / L. The As(III) treatment effect was 16% lower than that in Example 1, while the As(V) treatment effect was equivalent to that in Example 1.

[0045] Comparative Example 3 Step (1) of Example 1 was omitted, and an excess of calcium hydroxide (10 g / L) was directly used to react with the arsenic-containing wastewater, i.e., a technical method without carbonate mineral induction. The pH of the system after the reaction was 12.4. After testing, the remaining As(III) concentration in the treated water was 1.14 mg / L and the As(V) concentration was 0.23 mg / L. The As(III) treatment effect was 37% lower than that of Example 1, and the As(V) treatment effect was equivalent to that of Example 1. Figure 5 As shown, the calcium arsenic precipitate generated by the direct reaction of calcium hydroxide with arsenic-containing wastewater is a weakly crystalline nanosheet. This may be due to its low stability and high solubility, resulting in a significantly higher concentration of residual As(III) in the water than in Example 1. Arsenic-rich slag is obtained by solid-liquid separation. According to the "Hazardous Waste Identification Standard - Leaching Toxicity Identification (GB5085.3-2007)", the leaching toxicity test of arsenic was 1.83 mg / L, which is lower than the standard limit of 5 mg / L. The leaching toxicity test of the arsenic-rich slag after three months of storage was conducted, and the leaching toxicity of arsenic was 14.7 mg / L, which is significantly higher than the standard limit of 5 mg / L. This shows that the arsenic-rich slag obtained by the prior art cannot be stored stably for a long time.

[0046] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for enhanced treatment of acidic arsenic-containing wastewater, characterized in that: The steps include: (1) adding an excess amount of carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture so that the hydrogen ions in the arsenic-containing wastewater are neutralized and insoluble carbonate mineral particles remain in the system after the reaction; (2) introducing a calcium-containing compound into the system after the reaction in step (1), wherein the calcium-containing compound is alkaline when in contact with water, so that the calcium ions dissociated from the calcium-containing compound in contact with water react with As(III) and As(V) in the arsenic-containing wastewater to precipitate and crystallize to form insoluble Ca-As(III) minerals and Ca-As(V) minerals, wherein the crystallization of the Ca-As(III) minerals occurs on the surface of the carbonate minerals; after the reaction is completed, the solid and liquid are separated to obtain arsenic-rich slag and arsenic-removed liquid.

2. The method according to claim 1, wherein The pH of the acidic arsenic-containing wastewater is less than 2, the total arsenic concentration is 10-15000 mg / L, and the molar proportion of As(III) in the total arsenic is not less than 20%.

3. The method according to claim 1, wherein The pH of the acidic arsenic-containing wastewater is less than 1, the total arsenic concentration is 1000-10000 mg / L, and the molar proportion of As(III) in the total arsenic is not less than 50%.

4. The method according to claim 1, wherein In step (1), 10 to 500 g / L of carbonate mineral is added to the acidic arsenic-containing wastewater; and the mixture is stirred and reacted for 12 to 24 hours.

5. The method according to claim 1, wherein Step (1) adding carbonate minerals to the acidic arsenic-containing wastewater and stirring to react until the pH of the system is 8-9.

6. The method according to claim 1, wherein After the reaction in step (1), the mass ratio of the insoluble carbonate mineral particles remaining in the system to the As(III) in the system is 10-30:

1.

7. The method according to claim 1, wherein The acidic arsenic-containing wastewater contains sulfate, and step (1) includes the following sub-steps: (1-1) adding a carbonate mineral to the acidic arsenic-containing wastewater and stirring the mixture thoroughly to allow the carbonate mineral to react with a portion of the hydrogen ions in the wastewater to neutralize, and the dissociated calcium ions in the carbonate mineral to react with sulfate ions in the wastewater to form gypsum, and separating the solid and liquid to obtain gypsum slag and pre-neutralized arsenic-containing wastewater; the ratio of the molar amount of the carbonate mineral added in step (1-1) to the molar amount of sulfate ions in the wastewater is 1 to 3:1; and the pH of the system after the neutralization reaction is 1 to 2; (1-2) Further adding carbonate minerals to the pre-neutralized arsenic-containing wastewater in step (1-1) until the amount is excessive, and stirring to neutralize the remaining hydrogen ions in the arsenic-containing wastewater, and insoluble carbonate mineral particles remain in the system after the reaction.

8. The method according to claim 1, wherein The carbonate mineral in step (1) is one or more of calcite, dolomite, limestone, limestone and marble.

9. The method according to claim 1, wherein The calcium-containing compound in step (2) is one or more of calcium oxide, calcium hydroxide, quicklime, slaked lime and lime milk.

10. The method according to claim 1, wherein The molar ratio of calcium in the calcium-containing compound added in step (2) to arsenic in the wastewater is Ca / As of 0.5 to 5:1; and the pH of the system after the reaction is completed is 11.5 to 12.5.

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