A method for preparing elemental arsenic from high-arsenic acid wastewater using Me-C reduction method

Abstract

The present invention belongs to the field of environmental engineering and resource recovery technology, and specifically relates to a method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method. The present invention mainly uses micro-electrolysis to efficiently reduce arsenic in wastewater to a high-purity elemental state (As 0 ); first, Me-C is used to reduce arsenic in high-arsenic acid mine wastewater to obtain a crude arsenic product. Existing distillation technology is then used to further improve the purity of the arsenic product to obtain impurities and an arsenic-removed product. The impurities are returned to the reduction and arsenic extraction process to save costs. The low-arsenic solution is then neutralized and impurities removed to obtain a purified solution, which is then returned to the company's production process for reuse. This method combines the advantages of efficient wastewater purification with a high yield of elemental arsenic. While purifying the wastewater, elemental arsenic is recovered, and the arsenic content in the treated solution is significantly reduced, reducing subsequent processing costs.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering and resource recovery, and relates to a method for preparing elemental arsenic from high-arsenic acid wastewater by utilizing a Me-C reduction method. Background Art

[0002] In recent years, with the development of my country's metallurgical / chemical industry, arsenic-containing nonferrous metals and precious metal sulfide ores have been continuously mined and smelted, generating a large amount of high-arsenic acid wastewater, which has become a typical hazardous pollutant in mining, metallurgy and chemical industries. Among them, the mass concentration of arsenic in high-arsenic acid wastewater from mines can be as high as 30g / L. It is highly toxic and has high environmental mobility, posing a serious threat to ecology and human health. Although traditional treatment technologies such as sulfide precipitation and iron salt coagulation can partially remove arsenic, they have low efficiency (especially for As 3+ Due to drawbacks such as high sludge volumes (difficult secondary disposal of arsenic-containing hazardous waste), and the inability to recycle resources, it is difficult to meet increasingly stringent environmental standards (such as the 0.5mg / L arsenic concentration limit in my country's Integrated Wastewater Discharge Standard). In recent years, adsorption methods (activated carbon, modified materials) and membrane separation technologies (reverse osmosis) have improved treatment accuracy, but they are costly and susceptible to fluctuations in water quality.

[0003] At the same time, elemental arsenic (As 0 As a high-value-added material, gallium arsenide (GaAs) is a core raw material for compound semiconductors such as gallium arsenide (GaAs). It supports high-end industries such as 5G communications, photovoltaics, and infrared detection, with global demand growing at an annual rate of 8% to 10%. Currently, global annual production of elemental arsenic is approximately 50,000 to 60,000 tons, primarily extracted as a byproduct of copper and gold smelting, a process that carries high environmental costs.

[0004] In this context, the development of innovative technologies that combine pollution control and resource recovery has become an urgent need in the industry. Existing wastewater treatment processes only focus on the removal of arsenic, but ignore its potential economic value, resulting in tens of thousands of tons of arsenic resources being landfilled or solidified in the form of hazardous waste each year, which not only wastes resources but also increases environmental risks. Resource recovery technology based on reduction method has become a new trend. Patent CN 110777260B discloses a wet treatment process for preparing elemental arsenic. First, common reducing agents such as sulfur dioxide, sodium sulfite, sodium metabisulfite or sodium thiosulfate are used to reduce As(V) in arsenic-containing solutions or smelting waste acid to As(III). After adjusting the acidity of the solution with sulfuric acid, As(III) is further reduced to elemental arsenic using one or more of aluminum powder, iron powder, zinc powder or cadmium powder. Although this invention realizes the resource recovery of arsenic in arsenic-containing acidic wastewater through metal powder, it is necessary to control the system to be at a higher sulfuric acid concentration (50g / L~150g / L) and a higher reaction temperature (60℃~95℃), and the metal powder needs to be added in excess, which not only leads to a decrease in the purity of elemental arsenic but also requires higher energy consumption and increased production costs. In addition, the higher sulfuric acid concentration still requires higher processing costs. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for preparing elemental arsenic from high arsenic acid wastewater using Me-C reduction method, which can efficiently reduce arsenic in wastewater to a higher purity elemental state (As) by micro-electrolysis. 0 Me-C is a metal-carbon composite material. The present invention has the advantages of efficient wastewater purification and high elemental arsenic yield. Elemental arsenic is recovered while purifying wastewater. The arsenic content in the treated solution is greatly reduced, reducing subsequent processing costs. The metal reducing agent involved in the present invention can be recycled in the process under certain conditions, achieving waste treatment and turning waste into treasure.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0008] Step (1): Arsenic extraction by reduction: The metal-carbon composite material (Me-C) is mixed and stirred with high-arsenic acid wastewater from a mine to carry out a reduction arsenic extraction reaction. After the reaction is completed, solid-liquid separation is performed to obtain a filter residue and a filtrate; the filter residue is a crude arsenic product, which is refined and purified; the filtrate is a low-arsenic liquid, which enters the impurity removal process;

[0009] Step (2): Refining and purification: The crude arsenic product described in step (1) is purified by distillation at a temperature of 600°C to 700°C, and the arsenic vapor is condensed and collected to obtain a pure arsenic product, and the remaining impurities are returned to the reduction arsenic extraction process;

[0010] Step (3): Neutralization and impurity removal: A neutralizing and impurity-removing agent is added to the low-arsenic liquid described in step (1), and solid-liquid separation is performed after the reaction is completed to obtain low-arsenic slag and purified liquid; the purified liquid can be returned to the enterprise's production process, such as electrolytic refining; the low-arsenic slag is treated in a manner determined according to the arsenic content therein.

[0011] According to the above method, the metal in the metal-carbon composite material in step (1) is one or more of magnesium, aluminum, zinc, iron, tin, lead, and cadmium, and the carbon is elemental carbon. If there are two or more of the metals, the metals are mixed in an equimolar ratio; the mass ratio of the metal to the carbon is (0.3-0.8):1, the particle size of the metal and the carbon is not higher than 350 microns, and the metal and the carbon are mixed in proportion and then directly added to the high-arsenic wastewater from the mine, or carbon powder is first added to the high-arsenic wastewater from the mine and then the metal is added.

[0012] According to the above method, the source of the high-arsenic acid mine wastewater in step (1) includes but is not limited to a non-ferrous smelting process, and the high-arsenic acid mine wastewater contains: sulfuric acid concentration of 0.15% to 20%, arsenic content of 1g / L to 20g / L, copper content of 0g / L to 0.5g / L, zinc content of 0g / L to 1g / L, cadmium content of 0g / L to 0.5g / L, and iron content of 0.2g / L to 5g / L.

[0013] According to the above method, the conditions of the reduction and arsenic extraction reaction in step (1) are: reaction temperature of 0°C to 40°C, stirring speed of 400rpm to 800rpm, reaction time of 0.5h to 2h, and the amount of Me-C added is determined according to the molar ratio of the metal to the arsenic content in the high-arsenic acid wastewater from the mine. If the metal element contains aluminum, the molar ratio of aluminum to arsenic is (0.8 to 1.5):1. If the metal contains one or more of magnesium, zinc, iron, tin, lead, and cadmium, the molar ratio of the metal to arsenic is (1.2 to 2):1.

[0014] According to the above method, the crude arsenic product in step (1) is a mixture of elemental carbon and elemental arsenic, and also contains unreacted metal powder; the arsenic content in the low-arsenic solution is less than 50 mg / L.

[0015] According to the above method, the purity of the pure arsenic product obtained after refining the crude arsenic product in step (2) is not less than 99.0%, and the impurities are elemental carbon and unreacted metal powder, which can be returned to the reduction arsenic extraction process to save production costs.

[0016] According to the above method, the neutralizing and impurity-removing agent in step (3) is a slurry whose main component is calcium oxide or calcium hydroxide with a mass fraction of 10% to 20%.

[0017] According to the above method, the reaction conditions of the neutralization and impurity removal in step (3) are: the pH at the reaction end point is 5-6, the stirring speed is 400 rpm, and the reaction time is 1h-2h.

[0018] According to the above method, the purified liquid in step (3) is a pure sulfate solution, the cations of which are consistent with the added metal, and can be returned to the process for electrolytic regeneration and recycling.

[0019] According to the above method, the treatment method of the low-arsenic slag in step (3) is determined according to the arsenic content therein. When the arsenic content in the low-arsenic slag is lower than 0.1%, the low-arsenic slag can be sold as a building material-grade gypsum product; when the arsenic content in the low-arsenic slag is higher than 0.1%, it needs to be sent to a tailings pond for storage and treatment.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention first uses Me-C to reduce arsenic in high-arsenic acid wastewater from mines to obtain a crude arsenic product. Then, existing distillation technology is used to further improve the purity of the arsenic product to obtain impurities and arsenic-removed products. The impurities are returned to the reduction and arsenic extraction process to save costs. The low-arsenic liquid is neutralized and impurities are removed to obtain a purified liquid, which is returned to the company's production process for reuse.

[0022] After adding carbon powder to acidic wastewater, the metal (anode) and carbon (cathode) form a micro battery, and the metal loses electrons and is oxidized (Me→Me n+ +ne - ), electrons are transferred to As in the solution through the carbon group 3+ / As 5+ , driving it to be reduced to As 0 , the reaction principle is as follows:

[0023] 3Me+2H3AsO3+6H + =2As↓+3Me 2+ +6H2O (Me is one of magnesium, zinc, iron, tin, lead, and cadmium)

[0024] Al+H3AsO3+3H + =As↓+Al 3+ +3H2O.

[0025] The present invention has the advantages of efficient wastewater purification and high elemental arsenic yield. Elemental arsenic is recovered while purifying wastewater. The arsenic content in the treated solution is greatly reduced, reducing subsequent treatment costs. The metal reducing agent involved in the present invention can be recycled in the process under certain conditions, realizing waste treatment and turning waste into treasure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the present invention;

[0027] Figure 2 This is a SEM image of the filter residue in Example 1 of the present invention;

[0028] Figure 3 This is the energy spectrum of the filter residue in Example 1 of the present invention;

[0029] Figure 4 This is the EDS layered diagram of the filter residue in Example 1 of the present invention;

[0030] Figure 5 This is the SEM image of step (2) in Example 1 of the present invention;

[0031] Figure 6 The energy spectrum diagram of step (2) in Example 1 of the present invention;

[0032] Figure 7 This is the EDS layered diagram of step (2) in Example 1 of the present invention;

[0033] Figure 8 Distribution diagram of aluminum and arsenic elements in step (2) of Example 1 of the present invention;

[0034] in Figure 8 a is the distribution diagram of aluminum element, Figure 8 b is the distribution diagram of arsenic element. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the embodiments.

[0036] Example 1

[0037] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, such as Figure 1 , the specific steps are as follows:

[0038] Step (1): Arsenic extraction by reduction: Aluminum powder and activated carbon are mixed at a mass ratio of 0.3:1, with the particle size of both aluminum powder and activated carbon being ≤350μm, and then directly added to high-arsenic acid wastewater from the mine; the wastewater composition is 0.15% sulfuric acid concentration, 1g / L arsenic content, and 0.2g / L iron content. The conditions for the arsenic extraction reduction reaction are: controlling the reaction temperature to 0°C, stirring speed to 400rpm, and aluminum / arsenic molar ratio to 0.8:1; after reacting for 0.5 hours, solid-liquid separation is performed, and the filter residue contains elemental arsenic and unreacted aluminum powder. The arsenic concentration in the filtrate is reduced to 50mg / L. Figure 2 is the SEM picture of the filter residue, Figure 3 is the energy spectrum of the filter residue, Figure 4 This is the EDS layer diagram for this stage;

[0039] Step (2) Refining and Purification: The filter residue is heated to 600°C in a vacuum distillation furnace, and the arsenic vapor is condensed and collected to obtain elemental arsenic with a purity of 99.14%. The remaining aluminum powder and activated carbon are returned to the reduction and arsenic extraction process for recycling. Figure 5 is the SEM image of the elemental arsenic, Figure 6 is the energy spectrum of the elemental arsenic, Figure 7 is the EDS layered diagram of this stage, Figure 8 is the distribution diagram of aluminum and arsenic elements, where Figure 8 a is the distribution diagram of aluminum element, Figure 8 b is the distribution diagram of arsenic;

[0040] Step (3) neutralization and impurity removal: add 10% calcium hydroxide slurry to the filtrate, adjust the pH to 5.0, stir at 400 rpm, react for 1 hour, and then separate the solid and liquid; the arsenic content in the purified liquid is less than 0.1 mg / L, and the aluminum sulfate solution is returned to the electrolysis process; the impurity removal slag contains 0.15% arsenic (higher than 0.1%) and is sent to the tailings pond for storage.

[0041] Example 2

[0042] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0043] Step (1) Arsenic Reduction Extraction: Iron powder and graphite were mixed in a mass ratio of 0.8:1, with both iron powder and graphite having a particle size of ≤350 μm. The mixture was added separately (graphite was added first, followed by iron powder). The acidic mine wastewater had a sulfuric acid concentration of 20%, an arsenic content of 20 g / L, a copper content of 0.5 g / L, and an iron content of 5 g / L. The arsenic reduction extraction reaction conditions were: a reaction temperature of 40°C, a stirring speed of 800 rpm, and an iron / arsenic molar ratio of 2:1. After a 2-hour reaction, the arsenic concentration in the filtrate was 45 mg / L, and the filter residue contained elemental arsenic, unreacted iron powder, and graphite.

[0044] Step (2) Refining and Purification: The filter residue is purified by distillation, and the arsenic purity reaches 99.95%. The residual iron powder and graphite are returned to the reduction process.

[0045] Step (3) Neutralization and impurity removal: add 20% calcium oxide slurry, adjust the pH to 6.0, stir at 400 rpm, react for 2 hours, and then separate the solid and liquid to generate gypsum slag containing 0.05% arsenic (less than 0.1%), which is sold as building material grade gypsum; the purified liquid is a ferrous sulfate solution, which is reused in the smelting process.

[0046] Example 3

[0047] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0048] Step (1) arsenic extraction by reduction: zinc powder and biochar are mixed in a mass ratio of 0.5:1, the zinc powder particle size is ≤350 μm, and the acid mine wastewater contains 10% sulfuric acid, 10 g / L arsenic, 1 g / L zinc, and 0.5 g / L cadmium; the conditions for the arsenic extraction reduction reaction are: reaction temperature 25° C., stirring speed 600 rpm, and zinc / arsenic molar ratio 1.5:1; after reacting for 1 hour, solid-liquid separation is performed, the arsenic concentration of the filtrate is reduced to 20 mg / L, and the filter residue contains arsenic and unreacted zinc powder;

[0049] Step (2) refining and purification: the filter residue is heated to 700°C in a vacuum distillation furnace, and the arsenic vapor is condensed and collected to obtain elemental arsenic with a purity of 99.93%. The remaining zinc powder and activated carbon are returned to the reduction and arsenic extraction process for recycling;

[0050] Step (3) Neutralization and impurity removal: 15% calcium hydroxide slurry was added to the filtrate, the pH was adjusted to 5.5, the stirring speed was 400 rpm, and the reaction was carried out for 1.5 hours before solid-liquid separation; the purified liquid was a zinc sulfate solution with an arsenic content of 0.05 mg / L, which could be returned to production; the slag contained 0.08% arsenic (less than 0.1%) and was sold as building material-grade gypsum.

[0051] Example 4

[0052] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0053] Step (1) Arsenic extraction by reduction: magnesium powder and carbon nanotubes are added separately in a mass ratio of 0.6:1. The composition of the acid mine wastewater is 5% sulfuric acid, 5g / L arsenic, and 2g / L iron. The conditions for the arsenic extraction by reduction reaction are: controlling the reaction temperature at 10°C, stirring speed at 500rpm, and magnesium / arsenic molar ratio at 1.2:1. After reacting for 1.5 hours, solid-liquid separation is performed, and the filter residue contains elemental arsenic and unreacted magnesium powder. The arsenic concentration in the filtrate is 40mg / L.

[0054] Step (2) refining and purification: the filter residue is treated by vacuum distillation, and the arsenic purity reaches 99.91%. The residual impurities are returned to step (1) for reuse, thereby achieving efficient resource utilization;

[0055] Step (3) Neutralization and impurity removal: 18% calcium oxide slurry is added to the low-arsenic solution to adjust the pH to 5.8. After reacting for 1 hour, the solid and liquid are separated. The slag contains 0.07% arsenic (less than 0.1%) and is sold as building material-grade gypsum. The purified liquid is a magnesium sulfate solution with an arsenic content of less than 0.1 mg / L and can be returned to production.

[0056] Example 5

[0057] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0058] Step (1) Arsenic extraction by reduction: Tin powder and graphene are mixed in a mass ratio of 0.4:1 and directly added into acidic mine wastewater containing 15% sulfuric acid, 15 g / L arsenic, and 0.3 g / L cadmium; the conditions for the arsenic extraction by reduction reaction are: controlling the reaction temperature to 30°C, stirring at 700 rpm, a tin / arsenic molar ratio of 1.8:1, reacting for 2 hours, and then separating the solid and liquid. The filter residue contains elemental arsenic and unreacted tin powder, and the arsenic concentration in the filtrate is 35 mg / L;

[0059] Step (2) refining and purification: the filter residue is purified by distillation, the arsenic purity reaches 99.92%, and the residue is recycled to reduce the cost of raw materials;

[0060] Step (3) neutralization and impurity removal: adjust the pH of the filtrate obtained in step (1) to 5.2 with 10% calcium hydroxide slurry, stir the reaction for 1 hour, and then separate the solid and liquid; the purified liquid is a tin sulfate solution with an arsenic content of less than 0.5 mg / L, which can be returned to production; the filter residue contains 0.12% arsenic and is safely landfilled according to hazardous waste standards.

[0061] Example 6

[0062] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0063] Step (1) Arsenic Reduction Extraction: Lead powder and activated carbon were added to wastewater in a mass ratio of 0.7:1 (activated carbon added first, lead powder added second). The acidic mine wastewater contained 8% sulfuric acid, 8 g / L arsenic, and 3 g / L iron. The arsenic reduction extraction reaction conditions were a reaction temperature of 20°C, a stirring speed of 750 rpm, and a lead / arsenic molar ratio of 1.6:1. After a 2-hour reaction, solid-liquid separation was performed. The filter residue contained elemental arsenic and unreacted lead powder, and the arsenic concentration in the filtrate was 25 mg / L.

[0064] Step (2) refining and purification: the filter residue is purified by distillation, and the arsenic purity reaches 99.94%. The residual impurities are returned to step (1) for reuse, thereby achieving efficient resource utilization;

[0065] Step (3) Neutralization and impurity removal: 16% calcium oxide slurry is added to the low-arsenic solution to adjust the pH to 5.5. After reacting for 1 hour, the solid and liquid are separated. The slag contains 0.06% arsenic (less than 0.1%) and is sold as building material gypsum after processing. The purified liquid is a lead sulfate solution with an arsenic content of less than 0.5 mg / L and can be returned to production.

[0066] Example 7

[0067] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0068] Step (1) Arsenic Reduction Extraction: Cadmium powder and carbon black were mixed in a mass ratio of 0.5:1 and directly added to acidic mine wastewater containing 18% sulfuric acid, 18 g / L arsenic, and 0.8 g / L zinc. The arsenic reduction extraction reaction conditions were: a reaction temperature of 35°C, a stirring speed of 650 rpm, and a cadmium / arsenic molar ratio of 1.9:1. After a reaction time of 1.5 hours, solid-liquid separation was performed, and the residue was crude arsenic. The arsenic concentration in the filtrate was 40 mg / L.

[0069] Step (2) refining and purification: the filter residue is purified by distillation, and the arsenic purity reaches 99.96%. The remaining impurities are returned to step (1) for reuse, thereby reducing resource waste;

[0070] Step (3) neutralization and impurity removal: add 14% by mass of calcium hydroxide slurry to the filtrate obtained in step (1), adjust the pH of the system to 5.7, stir and react for 2 hours, and then separate the solid and liquid; the slag contains 0.18% arsenic and is stored. The purified liquid is cadmium sulfate solution with an arsenic content of less than 0.1 mg / L, and can be returned to production.

[0071] Example 8

[0072] A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, the specific steps are as follows:

[0073] Step (1) Arsenic extraction by reduction: A mixed aluminum-iron powder (Al:Fe=1:1) and activated carbon in a mass ratio of 0.3:1 are mixed and directly added to acidic mine wastewater containing 0.15% sulfuric acid, 1 g / L arsenic, and 0.5 g / L copper. The conditions for the arsenic extraction by reduction reaction are: controlling the reaction temperature to 0°C, stirring speed to 400 rpm, total metal / arsenic molar ratio to 1.2:1, reacting for 1 hour, and then separating the solid and liquid. The filter residue contains elemental arsenic and unreacted metal powder, and the arsenic concentration in the filtrate is 28 mg / L.

[0074] Step (2) refining and purification: the filter residue is purified by distillation, and the arsenic purity reaches 99.9%. The unreacted metal powder is returned to step (1) for recycling, thereby reducing production costs;

[0075] Step (3) neutralization and impurity removal: add 20% by mass of calcium hydroxide slurry to the filtrate obtained in step (1), adjust the pH of the system to 6.0, stir and react for 1.5 hours, and then separate the solid and liquid. The slag contains 0.2% arsenic and is stored. The purified liquid is aluminum sulfate solution with an arsenic content of less than 0.1 mg / L, and can be returned to production.

Claims

1. A method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method, characterized in that: The specific steps are as follows: Step (1): Arsenic extraction by reduction: the metal-carbon composite material is mixed and stirred with high-arsenic acid wastewater from a mine to carry out an arsenic extraction reduction reaction, and after the reaction is completed, solid-liquid separation is carried out to obtain a filter residue and a filtrate; the filter residue is a crude arsenic product, which is refined and purified; the filtrate is a low-arsenic liquid, which enters an impurity removal process; the metal in the metal-carbon composite material is one or more of magnesium, aluminum, zinc, iron, tin, lead, and cadmium, and the carbon is elemental carbon; Step (2): Refining and purification: The crude arsenic product described in step (1) is purified by distillation at a temperature of 600°C to 700°C, and the arsenic vapor is condensed and collected to obtain a pure arsenic product, and the remaining impurities are returned to the reduction arsenic extraction process; Step (3): Neutralization and impurity removal: A neutralizing and impurity removal agent is added to the low-arsenic liquid described in step (1), and solid-liquid separation is performed after the reaction is completed to obtain low-arsenic slag and purified liquid; the purified liquid can be returned to the enterprise's production process; the low-arsenic slag is treated in a manner determined according to the arsenic content therein.

2. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: If there are two or more metals in the metal-carbon composite material in step (1), the metals are mixed in an equimolar ratio; the mass ratio of the metal to the carbon is (0.3-0.8):1, the particle size of the metal and the carbon is not higher than 350 μm, and the metal and the carbon are mixed in proportion and then directly added to the high-arsenic wastewater from the mine, or carbon powder is first added to the high-arsenic wastewater from the mine and then the metal is added.

3. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The high-arsenic acid mine wastewater in step (1) has a source including but not limited to a non-ferrous smelting process, and the high-arsenic acid mine wastewater contains: sulfuric acid concentration of 0.15% to 20%, arsenic content of 1 g / L to 20 g / L, copper content of 0 g / L to 0.5 g / L, zinc content of 0 g / L to 1 g / L, cadmium content of 0 g / L to 0.5 g / L, and iron content of 0.2 g / L to 5 g / L.

4. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The conditions for the reduction and arsenic extraction reaction in step (1) are as follows: reaction temperature of 0°C to 40°C, stirring speed of 400rpm to 800rpm, reaction time of 0.5h to 2h, and the amount of Me-C added is determined according to the molar ratio of the metal to the arsenic content in the high-arsenic acid wastewater from the mine. If the metal element contains aluminum, the molar ratio of aluminum to arsenic is (0.8~1.5):1; if the metal element contains one or more of magnesium, zinc, iron, tin, lead, and cadmium, the molar ratio of the metal to arsenic is (1.2~2):

1.

5. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The crude arsenic product in step (1) is a mixture of elemental carbon and elemental arsenic, and also contains unreacted metal powder; the arsenic content in the low-arsenic solution is less than 50 mg / L.

6. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The purity of the pure arsenic product obtained after refining the crude arsenic product in step (2) is not less than 99.0%, and the impurities are elemental carbon and unreacted metal powder, which can be returned to the reduction arsenic extraction process to save production costs.

7. The method for preparing elemental arsenic from high-arsenic acid wastewater using Me-C reduction method according to claim 1, characterized in that: The neutralizing and impurity-removing agent in step (3) is a slurry whose main component is calcium oxide or calcium hydroxide with a mass fraction of 10% to 20%.

8. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The reaction conditions for neutralization and impurity removal in step (3) are as follows: pH at the reaction end point is 5-6, stirring speed is 400 rpm, and reaction time is 1 h-2 h.

9. The method for preparing elemental arsenic from high-arsenic acid wastewater using a Me-C reduction method according to claim 1, characterized in that: The purified liquid in step (3) is a pure sulfate solution, the cations of which are consistent with the added metal, and can be returned to the process for electrolytic regeneration and recycling.

10. The method for preparing elemental arsenic from high-arsenic acid wastewater using Me-C reduction method according to claim 1, characterized in that: The treatment method of the low-arsenic slag in step (3) is determined according to the arsenic content therein. When the arsenic content in the low-arsenic slag is lower than 0.1%, the low-arsenic slag can be sold as a building material-grade gypsum product; when the arsenic content in the low-arsenic slag is higher than 0.1%, it needs to be sent to a tailings pond for storage and treatment.

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