Method for preparing elemental arsenic from high-arsenic acid wastewater by Me-C reduction method

Abstract

The invention belongs to the technical field of environmental engineering and resource recovery, and particularly relates to a method for preparing elemental arsenic from high-arsenic acid wastewater by using a Me-C reduction method. According to the method, arsenic in the wastewater is efficiently reduced to be in a high-purity elemental state (As0) mainly through the micro-electrolysis effect; the method comprises the following steps: reducing arsenic in the mine high-arsenic acid wastewater by using Me-C to obtain a crude arsenic product, further improving the purity of the arsenic product by using an existing distillation technology to obtain impurities and an arsenic-removed product, returning the impurities to the reduction arsenic extraction process to save the cost, neutralizing and removing impurities from the low-arsenic liquid to obtain a purified liquid, and returning the purified liquid to the enterprise production process for recycling. The method has the advantages of efficient wastewater purification and high yield of the elemental arsenic, the elemental arsenic is recovered while the wastewater is purified, the arsenic content in the treated solution is greatly reduced, and the subsequent treatment cost is reduced.

Description

Technical Field

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

[0002] In recent years, with the development of China's metallurgical / chemical industries, the mining and smelting of arsenic-containing non-ferrous and precious metal sulfide ores have continuously generated a large amount of high-arsenic acidic wastewater, which has become a typical hazardous pollutant in industries such as mining, metallurgy, and chemical engineering. Among them, the mass concentration of arsenic in mine high-arsenic acidic wastewater can be as high as 30 g / L. Its toxicity is strong and its environmental mobility is high, posing a serious threat to the ecosystem and human health. Traditional treatment technologies such as sulfide precipitation method and ferric salt coagulation method can partially remove arsenic, but they have defects such as low efficiency (especially for As 3+ ), a large amount of sludge (difficult secondary disposal of arsenic-containing hazardous waste), and inability to be recycled, making it difficult to meet the increasingly strict environmental protection standards (such as the arsenic concentration limit of 0.5 mg / L in the Comprehensive Wastewater Discharge Standard of China). In recent years, although adsorption methods (activated carbon, modified materials) and membrane separation technologies (reverse osmosis) have improved the treatment accuracy, they are costly and vulnerable to water quality fluctuations.

[0003] At the same time, elemental arsenic (As 0 ) is a high-value-added material and the core raw material of compound semiconductors such as gallium arsenide (GaAs), supporting high-end industries such as 5G communication, photovoltaic, and infrared detection. The global annual demand growth rate reaches 8% - 10%. Currently, the global annual output of elemental arsenic is about 50,000 - 60,000 tons, mainly relying on the extraction from copper / gold smelting by-products, but the environmental protection cost in the smelting process is relatively high.

[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 as hazardous waste every year, which not only wastes resources but also exacerbates environmental risks. Resource recovery technologies based on reduction methods have 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 acids to As(III). Then, after adjusting the acidity of the solution with sulfuric acid, one or more of aluminum powder, iron powder, zinc powder, or cadmium powder are used to further reduce As(III) to elemental arsenic. Although this invention realizes the resource utilization of arsenic in arsenic-containing acidic wastewater through metal powders, it is necessary to control the system at a relatively high sulfuric acid concentration (50 g / L - 150 g / L) and a relatively high reaction temperature (60°C - 95°C), and the metal powders need to be added in excess, which not only reduces the purity of elemental arsenic but also consumes high energy, increasing production costs. In addition, a relatively high sulfuric acid concentration still requires a relatively high treatment cost. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method, which efficiently reduces arsenic in the wastewater to a relatively high-purity elemental state (As 0 ) through microelectrolysis. Where Me-C is a metal-carbon composite material. The present invention has the advantages of efficient wastewater purification and high elemental arsenic yield, recovering elemental arsenic while purifying the wastewater, greatly reducing the arsenic content in the treated solution, reducing subsequent treatment costs. The metal reducing agent involved in the present invention can be recycled in the process under certain conditions, realizing treating waste with waste and turning waste into treasure.

[0006] To achieve the above purpose, the present invention is realized by adopting the following technical solutions:

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

[0008] Step (1): Reduction and arsenic extraction: Mix the metal-carbon composite material (Me-C) with high-arsenic acidic wastewater from mines and stir to carry out the reduction and arsenic extraction reaction. After the reaction ends, carry out solid-liquid separation to obtain filter residue and filtrate; the filter residue is the crude arsenic product, which is refined and purified; the filtrate is the low-arsenic liquid, which enters the impurity removal process;

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

[0010] Step (3): Neutralization and impurity removal: Add a neutralization and impurity removal agent to the low-arsenic solution described in step (1). After the reaction ends, perform solid-liquid separation to obtain low-arsenic slag and purified solution. The purified solution can be returned to the enterprise production process, such as electrolytic refining. The treatment method of the low-arsenic slag is determined according to its arsenic content.

[0011] According to the above method, the metal in the metal-carbon composite material described 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 metals, the metals are proportioned in an equimolar ratio. The mass ratio of the metal to carbon is (0.3 - 0.8):1, the particle size of the metal and carbon is not higher than 350 microns, and after the metal and carbon are mixed in proportion, they are directly added to the high-arsenic acidic mine wastewater, or carbon powder is first added to the high-arsenic acidic mine wastewater and then the metal is added.

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

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

[0014] According to the above method, the crude arsenic product described 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%. The impurities are elemental carbon and unreacted metal powder, which can be returned to the reduction and arsenic extraction process to save production costs.

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

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

[0018] According to the above method, the purified liquid described in step (3) is a pure sulfate solution, and the cation of the sulfate solution is the same as the added metal, and it can be returned to the process for electrolytic regeneration and recycling application.

[0019] According to the above method, the treatment method of the low - arsenic slag described in step (3) is determined according to its arsenic content. When the arsenic content in the low - arsenic slag is less 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 the tailings pond for stacking 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 acidic mine wastewater to obtain a crude arsenic product. Subsequently, the existing distillation technology is used to further improve the purity of the arsenic product, obtaining an impurity - removed arsenic product. The impurity is returned to the arsenic reduction and extraction process to save costs, and the low - arsenic liquid is subjected to neutralization and impurity removal to obtain a purified liquid, which is returned to the enterprise production process for reuse.

[0022] After adding carbon powder to the acidic wastewater, a micro - battery is formed between the metal (anode) and carbon (cathode). The metal loses electrons and is oxidized (Me→Me n+ +ne - ), and the electrons are transferred through the carbon matrix to As 3+ / As 5+ in the solution, driving its reduction 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, cadmium)

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

[0025] The present invention has the advantages of both highly efficient wastewater purification and high elemental arsenic yield. While purifying the wastewater, elemental arsenic is recovered, and the arsenic content in the treated solution is greatly reduced, reducing the subsequent treatment cost. The metal reducing agent involved in the present invention can be recycled in the process under certain conditions, realizing waste treatment with waste and turning waste into treasure. Description of the Drawings

[0026] Figure 1 is the process flow chart related to the present invention;

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

[0028] Figure 3 Energy spectrum diagram of the filter residue in Example 1 of the present invention;

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

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

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

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

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

[0034] where Figure 8 a is the distribution diagram of aluminum element, Figure 8 b is the distribution diagram of arsenic element. Detailed implementation manners

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

[0036] Example 1

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

[0038] Step (1): Reduction and arsenic extraction: Mix aluminum powder and activated carbon in a mass ratio of 0.3:1, and the particle sizes of both aluminum powder and activated carbon are ≤ 350 μm, and directly put them into high-arsenic acidic wastewater in a mine; the wastewater components are sulfuric acid concentration 0.15%, arsenic content 1 g / L, and iron content 0.2 g / L. The conditions for the reduction and arsenic extraction reaction are: control the reaction temperature at 0 °C, the stirring speed at 400 rpm, and the aluminum / arsenic molar ratio at 0.8:1; after reacting for 0.5 hours, solid-liquid separation is carried out. The filter residue contains elemental arsenic and unreacted aluminum powder, and the arsenic concentration in the filtrate is reduced to 50 mg / L. Figure 2 is the SEM image of the said filter residue, Figure 3 is the energy spectrum diagram of the said filter residue, Figure 4 is the EDS stratification diagram at this stage;

[0039] Step (2) Refining and Purifying: Heat the filter residue in a vacuum distillation furnace to 600 °C. 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 arsenic reduction process for recycling. Figure 5 This is the SEM image of the elemental arsenic. Figure 6 This is the energy spectrum diagram of the elemental arsenic. Figure 7 This is the EDS stratification diagram at this stage. Figure 8 This 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 element;

[0040] Step (3) Neutralization and Impurity Removal: Add 10% calcium hydroxide slurry to the filtrate, adjust the pH to 5.0, with a stirring speed of 400 rpm. After reacting for 1 h, perform solid-liquid separation; the arsenic content in the purified liquid is <0.1 mg / L, which is a aluminum sulfate solution and is returned to the electrolysis process; the impurity removal residue contains 0.15% arsenic (higher than 0.1%) and is sent to the tailings pond for stacking.

[0041] Example 2

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

[0043] Step (1) Arsenic Reduction: Mix iron powder and graphite in a mass ratio of 0.8:1. The particle sizes of both iron powder and graphite are ≤350 μm, and they are added separately (graphite is added first and then iron powder); the composition of the mine acidic wastewater is sulfuric acid concentration 20%, arsenic content 20 g / L, copper content 0.5 g / L, and iron content 5 g / L; the conditions for the arsenic reduction reaction are: control the reaction temperature at 40 °C, stirring speed at 800 rpm, and iron / arsenic molar ratio at 2:1. After reacting for 2 hours, the arsenic concentration in the filtrate is 45 mg / L, and the filter residue contains elemental arsenic, unreacted iron powder and graphite.

[0044] Step (2) Refining and Purifying: The filter residue is purified by distillation, and the arsenic purity reaches 99.95%. The remaining 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, with a stirring speed of 400 rpm. After reacting for 2 h, perform solid-liquid separation. The generated gypsum residue contains 0.05% arsenic (lower than 0.1%) and is sold as building material grade gypsum; the purified liquid is a ferrous sulfate solution and is reused in the smelting process.

[0046] Example 3

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

[0048] Step (1) Reduction and arsenic extraction: Zinc powder and biochar are mixed at a mass ratio of 0.5:1, with the particle size of zinc powder ≤ 350 μm. The acidic mine wastewater contains 10% sulfuric acid, 10 g / L arsenic, 1 g / L zinc, and 0.5 g / L cadmium. The conditions for the reduction and arsenic extraction 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 carried out. The arsenic concentration in 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. 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 is added to the filtrate, the pH is adjusted to 5.5, and the stirring speed is 400 rpm. After reacting for 1.5 h, solid-liquid separation is carried out. The purified liquid is a zinc sulfate solution with an arsenic content of 0.05 mg / L, which can be returned to production. The residue contains 0.08% arsenic (lower than 0.1%) and is sold as building material grade gypsum.

[0051] Example 4

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

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

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

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

[0056] Example 5

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

[0058] Step (1) Reduction and arsenic extraction: Tin powder and graphene are mixed at a mass ratio of 0.4:1 and directly put into the acidic mine wastewater containing 15% sulfuric acid, 15 g / L arsenic, and 0.3 g / L cadmium. The conditions for the reduction and arsenic extraction reaction are as follows: control the reaction temperature at 30 °C, stir at 700 rpm, the molar ratio of tin / arsenic is 1.8:1. After reacting for 2 h, solid-liquid separation is carried out. 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, and the arsenic purity reaches 99.92%. The residue is recycled to reduce the raw material cost;

[0060] Step (3) Neutralization and impurity removal: Use 10% calcium hydroxide slurry to adjust the pH of the filtrate obtained in Step (1) to 5.2, stir and react for 1 h, and then carry out solid-liquid separation. The purified liquid is stannous sulfate solution with arsenic content 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 the hazardous waste standard.

[0061] Example 6

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

[0063] Step (1) Reduction and arsenic extraction: Lead powder and activated carbon are added to the wastewater in sequence (first add activated carbon and then add lead powder) at a mass ratio of 0.7:1. The composition of the acidic mine wastewater is 8% sulfuric acid, 8 g / L arsenic, and 3 g / L iron. The conditions for the reduction and arsenic extraction reaction are to control the reaction temperature at 20 °C, the stirring speed at 750 rpm, and the molar ratio of lead / arsenic at 1.6:1. After reacting for 2 hours, solid-liquid separation is carried out. The filter residue contains elemental arsenic and unreacted lead powder, and the arsenic concentration in the filtrate is 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 recycled to Step (1) for reuse, realizing efficient resource utilization;

[0065] Step (3) Neutralization and impurity removal: Add 16% calcium oxide slurry to the low-arsenic solution to adjust the pH to 5.5, react for 1 h, and then carry out solid-liquid separation. The residue contains 0.06% arsenic (less than 0.1%), and after processing, it is sold as building material gypsum; the purified liquid is lead sulfate solution with arsenic content less than 0.5 mg / L, which can be returned to production.

[0066] Example 7

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

[0068] Step (1) Reduction and arsenic extraction: Cadmium powder and carbon black are mixed at a mass ratio of 0.5:1 and directly put into the acidic mine wastewater containing 18% sulfuric acid, 18 g / L arsenic, and 0.8 g / L zinc. The conditions for the reduction and arsenic extraction reaction are: controlling the reaction temperature at 35 °C, the stirring speed at 650 rpm, and the cadmium / arsenic molar ratio at 1.9:1. After reacting for 1.5 hours, solid-liquid separation is carried out. The filter residue is crude arsenic, and the arsenic concentration in the filtrate is 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, reducing resource waste.

[0070] Step (3) Neutralization and impurity removal: Add 14% calcium hydroxide slurry by mass to the filtrate obtained in step (1), adjust the system pH to 5.7, stir and react for 2 h, and then carry out solid-liquid separation. The residue contains 0.18% arsenic and is stockpiled. The purified liquid is cadmium sulfate solution, and the arsenic content is less than 0.1 mg / L, which can be returned to production.

[0071] Example 8

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

[0073] Step (1) Reduction and arsenic extraction: Aluminum-iron mixed powder (Al:Fe = 1:1) and activated carbon are mixed at a mass ratio of 0.3:1 and directly put into the acidic mine wastewater. The sulfuric acid in the wastewater is 0.15%, arsenic is 1 g / L, and copper is 0.5 g / L. The conditions for the reduction and arsenic extraction reaction are: controlling the reaction temperature at 0 °C, the stirring speed at 400 rpm, and the total metal / arsenic molar ratio at 1.2:1. After reacting for 1 hour, solid-liquid separation is carried out. 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, reducing production costs.

[0075] Step (3) Neutralization and impurity removal: Add 20% calcium hydroxide slurry by mass to the filtrate obtained in step (1), adjust the system pH to 6.0, stir and react for 1.5 h, and then carry out solid-liquid separation. The residue contains 0.2% arsenic and is stockpiled. The purified liquid is aluminum sulfate solution, and the arsenic content is less than 0.1 mg / L, which can be returned to production.

Claims

1. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method, which is characterized in that, The specific steps are as follows: Step (1): Arsenic reduction and extraction: Mix the metal-carbon composite material (Me-C) with high-arsenic acidic mine wastewater and stir to carry out the arsenic reduction and extraction reaction. After the reaction, perform solid-liquid separation to obtain filter residue and filtrate. The filter residue is the crude arsenic product, which is refined and purified. The filtrate is the low-arsenic liquid and enters the impurity removal process. Step (2): Refining and purification: Purify the crude arsenic product described in step (1) by distillation method at a temperature of 600°C to 700°C. The arsenic vapor is condensed and collected to obtain the pure arsenic product, and the remaining impurities are returned to the arsenic reduction and extraction process. Step (3): Neutralization and impurity removal: Add a neutralization and impurity removal agent to the low-arsenic liquid described in step (1). After the reaction, perform solid-liquid separation to obtain low-arsenic residue and purified liquid. The purified liquid can be returned to the enterprise production process, such as electrolytic refining. The treatment method of the low-arsenic residue is determined according to its arsenic content.

2. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The metal in the metal-carbon composite material described 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 metals, each metal is proportioned in an equimolar ratio. The mass ratio of the metal to carbon is (0.3 - 0.8):

1. The particle sizes of the metal and carbon are not higher than 350 microns. After being mixed in proportion, the metal and carbon are directly added to the high-arsenic acidic mine wastewater, or carbon powder is first added to the high-arsenic acidic mine wastewater and then the metal is added.

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

4. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The conditions for the arsenic reduction and extraction reaction described in step (1) are: the reaction temperature is 0°C to 40°C, the stirring speed is 400 rpm to 800 rpm, the reaction time is 0.5 h to 2 h. The addition amount of Me-C is determined according to the molar ratio of the metal to the arsenic content in the high-arsenic acidic mine wastewater. If aluminum is contained in the metal element, the molar ratio of aluminum to arsenic is (0.8 - 1.5):

1. If one or more of magnesium, zinc, iron, tin, lead, and cadmium are contained in the metal, the molar ratio of the metal to arsenic is (1.2 - 2):

1.

5. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The crude arsenic product described 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 liquid is less than 50 mg / L.

6. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the 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 described in step (2) is not less than 99.0%. The impurities are elemental carbon and unreacted metal powder, which can be returned to the arsenic reduction and extraction process to save production costs.

7. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The neutralization and impurity removal agent described in step (3) is a slurry with calcium oxide or calcium hydroxide as the main component and a mass fraction of 10% - 20%.

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

9. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The purified liquid described in step (3) is a pure sulfate solution, and the cation of the sulfate solution is the same as the added metal, which can be returned to the process for electrolytic regeneration and recycled application.

10. A method for preparing elemental arsenic from high-arsenic acidic wastewater by using the Me-C reduction method according to claim 1, characterized in that, The treatment method of the low-arsenic slag described 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 the tailings pond for storage and treatment.

Images