A method for enhanced treatment of acidic wastewater containing arsenic
By combining carbonate minerals with calcium-containing compounds to treat acidic arsenic-containing wastewater, the problem of high cost in removing As(III) in existing technologies has been solved, achieving low-cost and high-efficiency arsenic removal and generating stable arsenic mineral slag.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDU UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2025-05-30
- Publication Date
- 2026-07-03
Smart Images
Figure CN120483354B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of arsenic pollution control, and more specifically, relates to an enhanced treatment method for acidic arsenic-containing wastewater. Background Technology
[0002] Acidic arsenic-containing wastewater is a common type of industrial wastewater in the non-ferrous metal smelting industry. Copper, lead, zinc, and other metallic elements are often associated with sulfur and arsenic. The SO2 flue gas generated during the smelting process is mainly used for industrial acid production, which also produces large amounts of acidic arsenic-containing wastewater. Because arsenic is highly toxic and an internationally recognized carcinogen, acidic arsenic-containing wastewater requires proper treatment.
[0003] Chemical precipitation is an effective method for treating arsenic-containing wastewater. It involves applying a precipitant to convert soluble arsenic into insoluble arsenic, thereby removing arsenic from the wastewater. In acidic arsenic-containing wastewater, arsenic exists in both As(III) and As(V) valence states, with As(III) being predominant. Due to differences in molecular structure, As(III) is generally more difficult to remove than As(V). Therefore, oxidants are often added to oxidize As(III) to As(V) to effectively treat As(III) in arsenic-containing wastewater. Patent documents CN117383752A and CN115677072A, among others, employ the addition of large amounts of oxidants to enhance As(III) removal. The oxidants involved include hydrogen peroxide, ozone, and calcium hypochlorite. These oxidants typically have high market prices, resulting in high treatment costs for acidic arsenic-containing wastewater. Summary of the Invention
[0004] In view of the shortcomings of the prior art, the purpose of this application is to provide an enhanced treatment method for acidic arsenic-containing wastewater, which aims to solve the technical problems of existing technologies for removing arsenic, especially trivalent arsenic, from acidic arsenic-containing wastewater, which require the addition of a large amount of oxidant to oxidize all As(III) to As(V), resulting in large reagent consumption and high treatment costs.
[0005] To achieve the above objectives, in a first aspect, this application provides an enhanced treatment method for acidic arsenic-containing wastewater, comprising the following steps:
[0006] (1) Add carbonate minerals to acidic arsenic-containing wastewater in excess, stir to neutralize the hydrogen ions in the arsenic-containing wastewater, and after the reaction, there are still insoluble carbonate mineral particles remaining in the system.
[0007] (2) Introduce a calcium-containing compound into the system after the reaction in step (1). The calcium-containing compound is alkaline when it comes into contact with water. The calcium ions dissociated from the calcium-containing compound react with As(III) and As(V) in the arsenic-containing wastewater to precipitate and crystallize into insoluble Ca-As(III) minerals and Ca-As(V) minerals. The crystallization of Ca-As(III) minerals occurs on the surface of carbonate minerals. After the reaction is completed, the solid and liquid are separated to obtain arsenic-rich slag and arsenic-removed liquid.
[0008] Preferably, in step (1), the amount of carbonate minerals added to the acidic arsenic-containing wastewater is 10~500 g / L; and the reaction time is 12~24 hours.
[0009] Preferably, in step (1), carbonate minerals are added to the acidic arsenic-containing wastewater and stirred to allow the system to react until the pH of the system is 8-9.
[0010] Preferably, the mass ratio of the remaining insoluble carbonate mineral particles in the system after step (1) to the mass of As(III) in the system is 10~30:1.
[0011] Preferably, the acidic arsenic-containing wastewater contains sulfate ions, and step (1) includes the following sub-steps:
[0012] (1-1) Add carbonate minerals to acidic arsenic-containing wastewater and stir thoroughly to neutralize some of the hydrogen ions in the wastewater. The calcium ions dissociated from the carbonate minerals react with the sulfate ions in the wastewater to form gypsum. Separate the solid and liquid to obtain gypsum residue and pre-neutralized arsenic-containing wastewater. The molar ratio of the carbonate minerals added in step (1-1) to the molar ratio of sulfate ions in the wastewater is 1~3:1. The pH of the system after neutralization is 1~2.
[0013] (1-2) Add carbonate minerals to the pre-neutralized arsenic-containing waste liquid in step (1-1) until the amount is excessive, and stir to neutralize the remaining hydrogen ions in the arsenic-containing waste liquid, and after the reaction, there are still insoluble carbonate mineral particles in the system.
[0014] Preferably, the molar ratio of calcium in the calcium-containing compound added in step (2) to arsenic in the wastewater is 0.5~5:1 (Ca / As); and the pH of the system after the reaction is completed is 11.5~12.5.
[0015] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:
[0016] (1) The present invention provides a method for carbonate mineral-enhanced crystallization treatment of acidic arsenic-containing wastewater. Based on the structural compatibility between carbonate minerals and calcium arsenite minerals, the interfacial interaction of carbonate minerals induces the epitaxial crystallization of calcium arsenite minerals. Compared with 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, thus enhancing the removal of As(III) from wastewater.
[0017] (2) Compared with traditional methods that enhance As(III) removal by adding large amounts of oxidants, the carbonate minerals used in this invention have a significant cost advantage. For example, the market price of common oxidants such as hydrogen peroxide and bleaching powder is around RMB 1,000 per ton, while the market price of carbonate minerals such as limestone used in this invention is only RMB 70-80 per ton, which is far lower than the market price of oxidants. This invention utilizes inexpensive carbonate minerals to enhance As(III) removal, avoiding the use of large amounts of oxidants and effectively reducing treatment costs.
[0018] (3) The carbonate mineral enhanced crystallization treatment method for acidic arsenic-containing wastewater proposed in this invention can reduce As(III) to 0.8 ppm and As(V) to 0.2 ppm at a very low cost, which facilitates the deep removal of arsenic from the wastewater. Moreover, the Ca-As(III) crystal minerals induced by the carbonate mineral interface of this invention have better long-term stability than the weakly crystalline Ca-As(III) products generated by direct precipitation of arsenic with calcium hydroxide in the prior art. They are also more resistant to the decomposition of carbon dioxide in the environment, which is more conducive to the temporary storage and safe landfill of the resulting arsenic-rich slag.
[0019] (4) The carbonate minerals used in this invention have multiple functions such as enhancing As(III) removal, neutralizing wastewater acidity and promoting gypsum formation, which can realize the efficient utilization of carbonate minerals.
[0020] (5) The materials used in this invention are simple, using only carbonate minerals and calcium-containing compounds, which can improve the operability and convenience of the processing system. Attached Figure Description
[0021] Figure 1 This is a schematic flowchart of an enhanced treatment method for acidic arsenic-containing wastewater provided in Embodiment 1 of this application;
[0022] Figure 2 These are scanning electron microscope images of calcite and its surface epitaxial crystalline calcium arsenite minerals before and after the reaction in Example 1 of this application;
[0023] Figure 3 This is a scanning electron microscope image of calcium arsenate minerals scattered on the surface of calcite in Example 1 of this application;
[0024] Figure 4 This is a schematic flowchart of an enhanced treatment method for acidic arsenic-containing wastewater provided in Embodiment 3 of this application;
[0025] Figure 5 This is a scanning electron microscope image of the calcium and arsenic precipitate obtained by directly reacting calcium hydroxide with arsenic-containing wastewater in Comparative Example 3 of this application. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.
[0027] The present invention provides an enhanced treatment method for acidic arsenic-containing wastewater, comprising the following steps:
[0028] (1) Add carbonate minerals to acidic arsenic-containing wastewater in excess, stir to neutralize the hydrogen ions in the arsenic-containing wastewater, and after the reaction, there are still insoluble carbonate mineral particles remaining in the system.
[0029] (2) A calcium-containing compound is introduced into the system after the reaction in step (1). This calcium-containing compound is alkaline when it comes into contact with water, causing the calcium ions released from the calcium-containing compound to react with As(III) and As(V) in the arsenic-containing wastewater, precipitating and crystallizing to form insoluble Ca-As(III) minerals and Ca-As(V) minerals. The crystallization of Ca-As(III) minerals occurs on the surface of carbonate minerals. After the reaction, 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.
[0030] The treatment method of this 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 and a total arsenic concentration of 10~15000 mg / L, wherein the molar percentage 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 and a total arsenic concentration of 1000~10000 mg / L, wherein the molar percentage of As(III) in the total arsenic is not less than 50%.
[0031] In some embodiments, in step (1), the amount of carbonate minerals added to the acidic arsenic-containing wastewater is 10~500 g / L, preferably 10~300 g / L; and the reaction time is 12~24 hours.
[0032] In some embodiments, step (1) involves adding carbonate minerals to acidic arsenic-containing wastewater and stirring to allow the system to react until the pH of the system is 8-9.
[0033] In some embodiments, the mass ratio of the remaining insoluble carbonate mineral particles in the system after step (1) to the mass of As(III) in the system is 10~30:1.
[0034] In other embodiments, for cases where acidic arsenic-containing wastewater contains sulfate ions, step (1) may include the following sub-steps:
[0035] (1-1) Add carbonate minerals to acidic arsenic-containing wastewater and stir thoroughly to neutralize some of the hydrogen ions in the wastewater. The calcium ions dissociated from the carbonate minerals react with the sulfate ions in the wastewater to form gypsum. Separate the solid and liquid to obtain gypsum residue and pre-neutralized arsenic-containing wastewater. The molar ratio of the carbonate minerals added in step (1-1) to the molar ratio of sulfate ions in the wastewater is 1~3:1. The pH of the system after neutralization is 1~2.
[0036] (1-2) Add carbonate minerals to the pre-neutralized arsenic-containing waste liquid in step (1-1) until the amount is excessive, and stir to neutralize the remaining hydrogen ions in the arsenic-containing waste liquid, and after the reaction, there are still insoluble carbonate mineral particles in the system.
[0037] The main component of the carbonate minerals in this invention is calcium carbonate. The carbonate minerals mentioned in step (1) include, but are not limited to, one or more of calcite, dolomite, limestone, limestone, and marble. The calcium-containing compounds mentioned in step (2) include, but are not limited to, one or more of calcium oxide, calcium hydroxide, quicklime, slaked lime, and lime milk.
[0038] In some embodiments, the molar ratio of calcium in the calcium-containing compound added in step (2) to arsenic in the wastewater, Ca / As, is 0.5~5:1, preferably 0.5~2:1; the pH of the system after the reaction is completed is 11.5~12.5.
[0039] Existing technologies treat acidic arsenic-containing wastewater by directly adding calcium oxide or calcium hydroxide. The main principle is to utilize the direct precipitation reaction between calcium ions and arsenic ions to reduce the arsenic concentration in the wastewater. However, due to the lack of process control over the calcium-arsenic precipitation reaction, only precipitates with poor crystallinity, small size, and high solubility are obtained. Furthermore, the weakly crystalline Ca-As(III) products generated by direct precipitation of arsenic with calcium hydroxide have poor long-term stability and cannot effectively resist the decomposition of carbon dioxide in the environment. This invention, by adding carbonate minerals, utilizes the structural compatibility between carbonate minerals and calcium arsenite minerals, using the carbonate mineral interface as a substrate to control the calcium-arsenic precipitation crystallization process. This improves the crystallinity and crystal size of the calcium-arsenic precipitate and reduces its solubility, reducing the As(III) concentration to 0.8 mg / L and significantly improving its long-term stability. In the field of arsenic-containing wastewater treatment, reducing the arsenic concentration from thousands of mg / L to a few mg / L may not be difficult; however, achieving further reductions in arsenic concentration, such as even a reduction of 0.1 mg / L, is extremely challenging. By utilizing the technical solution of this invention and improving traditional methods with inexpensive and readily available carbonate minerals, the As(III) concentration can be further reduced by nearly 30%, achieving unexpected technological progress.
[0040] The embodiments of the present invention are implemented under 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 in accordance with conventional conditions.
[0041] The endpoints and any values of the ranges disclosed in this invention 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 endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.
[0042] The process parameters in the following examples, unless otherwise specified, are generally performed under conventional conditions.
[0043] The embodiments of this application are described below with reference to the accompanying drawings.
[0044] Example 1
[0045] The acidic arsenic-containing wastewater has a pH of 1.3 and a total arsenic concentration of 1150 mg / L, of which the As(III) concentration is 1130 mg / L and the As(V) concentration is 20 mg / L.
[0046] This embodiment addresses the acidic arsenic-containing wastewater by employing... Figure 1The steps shown are processed as follows:
[0047] (1) Add 20 g / L of calcite to the acidic arsenic-containing wastewater, stir continuously, and react for 12 hours; the pH of the suspension after the reaction is 8.5, and excess calcite particles are visible, and the mass ratio of excess calcite particles to As(III) is 15:1.
[0048] (2) Add 1 g / L of calcium hydroxide to the system after the reaction in step (1), stir continuously, and react for 24 hours; the pH of the suspension after the reaction is 12.3;
[0049] (3) Separate the solid and liquid of the suspension after the reaction in step (2) to obtain arsenic-rich slag and arsenic-removed liquid.
[0050] The test results showed that the residual As(III) concentration in the arsenic-removed solution was 0.83 mg / L and the As(V) concentration was 0.24 mg / L, with an As(III) removal rate of 99.93% and an As(V) removal rate of 98.80%.
[0051] The arsenic-rich slag obtained in step (3) was subjected to scanning electron microscopy analysis, such as... Figure 2 As shown in Figures (a), (b), and (c), Figure (a) is a scanning electron microscope (SEM) image of calcite before the reaction, Figure (b) is a SEM image of the arsenic-rich slag after the reaction, and Figure (c) is a magnified view of a portion of Figure (b). It can be observed that a large number of well-crystallized calcium arsenite plate-like crystals were formed on the surface of the calcite mineral after the reaction. These crystals are arranged in an orderly manner on the surface of the calcite mineral in a vertical growth pattern, with crystal sizes ranging from 0.3 to 0.8 micrometers laterally and 0.9 to 1.3 micrometers vertically. The calcite {104} surface originally had smooth cleavage planes, indicating that the presence of calcite during the reaction regulated the crystallization process of the calcium arsenite minerals, inducing the formation of large-sized, highly crystalline, and low-solubility products, playing an important role in enhancing the deep removal of arsenic.
[0052] Meanwhile, arsenic-rich slag after the reaction was also observed to contain substances such as... Figure 3As shown in the SEM image, calcium arsenate does not exhibit a strong interaction with the calcite mineral surface compared to calcium arsenite. Therefore, it is inferred that the crystallization of Ca-As(V) minerals occurs in solution, rather than on the calcite mineral surface. Compared to Comparative Example 3, which directly uses calcium hydroxide for arsenic removal, the residual As(III) concentration in the arsenic-removed solution 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 comparable As(V) concentrations also indicate that the crystallization removal of As(V) mainly occurs in solution, while the introduction of carbonate minerals significantly promotes the removal of As(III), further demonstrating the strong interaction between calcium arsenite and the calcite mineral surface.
[0053] The arsenic-rich slag obtained was subjected to leaching toxicity testing according to the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification (GB5085.3-2007)". The leaching concentration of arsenic was 1.22 mg / L, which is lower than the limit of 5 mg / L in the standard. The leaching toxicity test was carried out on the arsenic-rich slag after 3 months of storage. The leaching concentration of arsenic was 1.31 mg / L, which is still lower than the standard limit. This shows that the arsenic-rich slag obtained by this invention can be stably stored for a long time.
[0054] Example 2
[0055] The acidic arsenic-containing wastewater has a pH of 0.8 and a total arsenic concentration of 11380 mg / L, of which As(III) concentration is 7660 mg / L and As(V) concentration is 3720 mg / L.
[0056] This embodiment addresses the acidic arsenic-containing wastewater by employing... Figure 1 The steps shown are processed as follows:
[0057] (1) Add 210 g / L of limestone to the acidic arsenic-containing wastewater and stir continuously for 12 hours; the pH of the suspension after the reaction is 8.6, and excess limestone particles are visible, and the mass ratio of excess limestone particles to As(III) is 20:1.
[0058] (2) Add 13 g / L of calcium oxide to the system after the reaction in step (1), stir continuously, and react for 24 hours; the pH of the suspension after the reaction is 12.2;
[0059] (3) Separate the solid and liquid of the suspension after the reaction in step (2) to obtain arsenic-rich slag and arsenic-removed liquid.
[0060] The test results showed that the residual As(III) concentration in the arsenic-removed solution was 0.82 mg / L and the As(V) concentration was 0.25 mg / L, with an As(III) removal rate of 99.989% and an As(V) removal rate of 99.993%.
[0061] Example 3
[0062] The acidic arsenic-containing wastewater has a pH of 0.5, a sulfate concentration of 9800 mg / L, a total arsenic concentration of 6510 mg / L, of which As(III) concentration is 5240 mg / L and As(V) concentration is 1270 mg / L.
[0063] This embodiment addresses the acidic arsenic-containing wastewater by employing... Figure 4 The steps shown are processed as follows:
[0064] (1) Add 14 g / L of calcite to the acidic arsenic-containing wastewater, stir continuously, and react for 12 hours; the pH of the suspension after the reaction is 1.5;
[0065] (2) Separate the solid and liquid components of the suspension after the reaction in step (1) to obtain gypsum residue and arsenic-containing liquid;
[0066] (3) Add 95 g / L of calcite to the arsenic-containing solution obtained in step (2), stir continuously, and react 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;
[0067] (4) Add 9 g / L of calcium hydroxide to the system after the reaction in step (3), stir continuously, and react for 24 hours; the pH of the suspension after the reaction is 12.3;
[0068] (5) Separate the solid and liquid of the suspension after the reaction in step (4) to obtain arsenic-rich slag and arsenic-removed liquid.
[0069] The test results showed that the concentration of As(III) in the arsenic-removed solution obtained in step (5) was 0.84 mg / L and the concentration of As(V) was 0.23 mg / L. The removal rate of As(III) was 99.984% and the removal rate of As(V) was 99.982%.
[0070] Comparative Example 1
[0071] The rest is the same as in Example 1, except that the carbonate minerals added in step (1) were not in excess, that is, the amount of calcite added was 2 g / L. The pH of the suspension after the reaction in step (1) was 2.1, and there were no residual calcite particles. 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.
[0072] Comparative Example 2
[0073] The rest is the same as in Example 1, except that the amount of carbonate minerals added in step (1) is excessive, but not excessive, that is, the amount of calcite added is only 10 g / L. The pH of the suspension after the reaction in step (1) is 8.4, in which excess calcite particles are visible, and the mass ratio of excess calcite particles to As(III) is 6:1. The pH of the suspension after the reaction in step (2) is 12.3. The concentration of As(III) remaining in the arsenic-removed liquid obtained in step (3) is 0.96 mg / L and the concentration of As(V) is 0.24 mg / L. The As(III) treatment effect is 16% lower than that in Example 1, while the As(V) treatment effect is comparable to that in Example 1.
[0074] Comparative Example 3
[0075] 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 non-carbonate mineral-induced method. The pH of the system after the reaction was 12.4. Testing showed that the residual 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, while the As(V) treatment effect was comparable to that of Example 1. Figure 5 As shown, the calcium arsenic precipitate formed by the direct reaction of calcium hydroxide with arsenic-containing wastewater is a weakly crystalline nanosheet. Its low stability and high solubility may result in a significantly higher residual As(III) concentration in the water compared to Example 1. Solid-liquid separation yielded arsenic-rich slag. Leaching toxicity testing was conducted according to the "Identification Standard for Hazardous Waste—Leaching Toxicity Identification (GB5085.3-2007)". The arsenic leaching concentration was 1.83 mg / L, lower than the standard limit of 5 mg / L. However, after three months of storage, the arsenic-rich slag underwent leaching toxicity testing again, resulting in an arsenic leaching concentration of 14.7 mg / L, significantly higher than the standard limit of 5 mg / L. This indicates that the arsenic-rich slag obtained using existing technology cannot be stably stored for extended periods.
[0076] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for enhanced treatment of acidic arsenic-containing wastewater, characterized in that, Includes the following steps: (1) Add carbonate minerals to acidic arsenic-containing wastewater in excess, stir to neutralize the hydrogen ions in the arsenic-containing wastewater, and after the reaction, there are still insoluble carbonate mineral particles remaining in the system; the carbonate minerals are one or more of calcite, limestone, limestone and marble. (2) Introduce a calcium-containing compound into the system after the reaction in step (1). The calcium-containing compound is alkaline when it comes into contact with water. The calcium ions dissociated from the calcium-containing compound 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. The crystallization of Ca-As(III) minerals occurs on the surface of carbonate minerals. After the reaction is completed, the solid and liquid are separated to obtain arsenic-rich slag and arsenic-removed liquid. The calcium-containing compound is calcium oxide and / or calcium hydroxide.
2. The method as described in claim 1, characterized in that, The acidic arsenic-containing wastewater has a pH of less than 2 and a total arsenic concentration of 10~15000 mg / L, wherein the molar percentage of As(III) in the total arsenic is not less than 20%.
3. The method as described in claim 1, characterized in that, The acidic arsenic-containing wastewater has a pH less than 1 and a total arsenic concentration of 1000~10000 mg / L, wherein the molar percentage of As(III) in the total arsenic is not less than 50%.
4. The method as described in claim 1, characterized in that, Step (1) Add 10~500 g / L of carbonate minerals to the acidic arsenic-containing wastewater; stir for 12~24 hours to allow the reaction to proceed.
5. The method as described in claim 1, characterized in that, Step (1) Add carbonate minerals to acidic arsenic-containing wastewater and stir to allow it to react until the pH of the system is 8-9.
6. The method as described in claim 1, characterized in that, After step (1), the mass ratio of the remaining insoluble carbonate mineral particles in the system to the mass of As(III) in the system is 10~30:
1.
7. The method as described in claim 1, characterized in that, The acidic arsenic-containing wastewater contains sulfate ions, and step (1) includes the following sub-steps: (1-1) Add carbonate minerals to acidic arsenic-containing wastewater and stir thoroughly to neutralize some of the hydrogen ions in the wastewater. The calcium ions dissociated from the carbonate minerals react with the sulfate ions in the wastewater to form gypsum. Separate the solid and liquid to obtain gypsum residue and pre-neutralized arsenic-containing wastewater. The molar ratio of the carbonate minerals added in step (1-1) to the molar ratio of sulfate ions in the wastewater is 1~3:
1. The pH of the system after neutralization is 1~2. (1-2) Add carbonate minerals to the pre-neutralized arsenic-containing waste liquid in step (1-1) until the amount is excessive, and stir to neutralize the remaining hydrogen ions in the arsenic-containing waste liquid, and after the reaction, there are still insoluble carbonate mineral particles in the system.
8. The method as described in claim 1, characterized in that, The calcium in the calcium-containing compound added in step (2) has a molar ratio of 0.5 to 5:1 with the arsenic in the wastewater; the pH of the system after the reaction is completed is 11.5 to 12.5.