An electrochemical device for removing As(III) from aqueous solution by self-alkalization

Abstract

The present invention provides an electrochemical device for removing As(III) from an aqueous solution by self-alkalization, comprising a closed electrolytic cell, an anion exchange membrane arranged in the electrolytic cell, a cathode current collector and an anode current collector arranged on both sides of the anion exchange membrane, the cathode current collector being a hydrogen peroxide generating electrode, a water treatment chamber being formed between the cathode current collector and the anion exchange membrane, the anode current collector being attached to the anion exchange membrane, and a flow channel for the flow of an anode suspension being formed between the two, the anode suspension being an electrolyte having an oxidative adsorption effect on As(III), and further comprising a sewage circulation device and a suspension circulation device, the two ends of the pipeline of the sewage circulation device being respectively connected to the water treatment chamber, and the two ends of the suspension circulation device being respectively connected to the flow channel. The electrochemical device of the present invention can form a continuous self-alkalization electrochemical system to promote the dissociation and oxidation of As(III), and oxidize and adsorb As(III) at the anode.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to an electrochemical device for removing As(III) in an aqueous solution by self-alkalization. Background Art

[0002] Arsenic (As) pollution in water bodies is an environmental issue of great significance worldwide. Inorganic As is highly toxic and has no beneficial metabolic function (Podgorski and Berg, 2020). Accumulation of inorganic As in the human body can cause skin diseases, nervous system disorders and even cancer. As in the diet mainly comes from contaminated drinking water, especially groundwater. It is reported that approximately 94 million to 220 million people worldwide drink groundwater that may be contaminated with high concentrations of As. Therefore, it is necessary to reduce the As concentration in drinking water to meet the maximum As concentration standard set by the World Health Organization (10μgL −1 ) is crucial.

[0003] The toxicity of inorganic As in water is significantly related to its valence state. Arsenite (As(III)) and arsenate (As(V)) are the main forms of inorganic As in aqueous solution. In an oxidizing environment, As mainly exists as As(V), while in a reducing environment (especially groundwater), As mainly exists as As(III). Uncharged As(III) (H 3 AsO 3 ) has a much higher migration capacity than As(V) (mainly HAsO 4 2− and H 2 AsO 4− ), whose toxicity is also dozens of times that of As(V). In the treatment of As(III)-contaminated water, As(III) is pre-oxidized to convert it into H 2 AsO 4 2− or HAsO 4 − It is a necessary condition for achieving efficient removal of As(III). Electrochemical water treatment technologies such as electrocoagulation and electrocatalytic oxidation can achieve good results in As(III) oxidation and removal. However, these processes usually have shortcomings. For example, the use of iron anode electrocoagulation to produce iron hydroxide induces As(III) oxidation and adsorbs and fixes the formed As(V), and solid waste is also generated in the process. In electrocatalytic oxidation, anodes composed of precious metals (such as Au, Pt and Pd) can effectively oxidize As(III) and adsorb As(V). However, the high cost of anode materials greatly limits its application prospects. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides an electrochemical device for removing As(III) in aqueous solution by self-alkalization and a method for removing As(III) in sewage using the device, which can achieve efficient removal of As(III) in water and has a simple structure and low cost.

[0005] The technical solution of the present invention to solve the above technical problems is as follows:

[0006] An electrochemical device for removing As(III) from an aqueous solution by self-alkalization, comprising a sealed electrolytic cell, an anion exchange membrane arranged in the electrolytic cell, a cathode current collecting plate and an anode current collecting plate arranged on both sides of the anion exchange membrane, the cathode current collecting plate and the anode current collecting plate being respectively connected to an external power supply, characterized in that the cathode current collecting plate is a hydrogen peroxide generating electrode, a water treatment chamber is formed between the cathode current collecting plate and the anion exchange membrane, the anode current collecting plate is bonded to the anion exchange membrane, and a flow channel for the flow of an anode suspension is formed therebetween, the flow channel is etched on a side of the anode current collector close to the anion exchange membrane, the anode suspension is an electrolyte having an oxidative adsorption effect on As(III), and also comprising a sewage circulation device and a suspension circulation device, the two ends of the pipeline of the sewage circulation device being respectively connected to the water treatment chamber, and the two ends of the suspension circulation device being respectively connected to the flow channel.

[0007] The working principle and beneficial effect of the present invention are as follows: by applying voltage in the system, dissolved oxygen is electrochemically reduced on the surface of the cathode current collector to generate hydrogen peroxide, and at the same time, the cathode adsorbs H 2 O dissociation produces H + Will promote OH − The two processes together promote the increase of pH value of the polluted aqueous solution, i.e., self-alkalization. The increase in pH directly leads to the dissociation of the electrically neutral As(III) into H 2 AsO 3 − and HAsO 3 2− , and then can migrate through the anion exchange membrane to the flow channel on the anode current collector under the action of the electric field force. In addition, the formed hydrogen peroxide can oxidize As(III) to As(V), and can also migrate to the flow channel on the anode current collector. As(V) migrated to the flow channel can be directly adsorbed by the anode suspension, and As(III) can be oxidized by the anode suspension to As(V) and finally adsorbed. The formed continuous self-alkalization electrochemical system promotes the dissociation and oxidation of As(III), thereby significantly enhancing the removal effect of As(III).

[0008] Furthermore, the surfaces of the water treatment chamber in contact with the inner wall of the electrolytic cell are provided with silicone gaskets.

[0009] The beneficial effect of adopting the above further solution is that the silicone gasket can seal the water treatment chamber.

[0010] Furthermore, the cathode current collecting plate and the anode current collecting plate are respectively attached to the adjacent end plates of the electrolytic cell.

[0011] The beneficial effect of adopting the above further solution is that the entire electrochemical device is compactly arranged.

[0012] Furthermore, the cathode current collecting plate and the corresponding positions on the electrolytic cell end plate attached thereto are provided with openings to form a water inlet channel, and the two ends of the water inlet channel are respectively connected to the water outlet end of the sewage circulation device and the water treatment chamber, and the anion exchange membrane, the anode current collecting plate and the corresponding positions on the electrolytic cell end plate attached thereto are provided with openings to form a water outlet channel, and the water outlet channel does not pass through the flow channel, and the two ends of the water outlet channel are respectively connected to the water treatment chamber and the water inlet end of the sewage circulation device.

[0013] The beneficial effect of adopting the above further scheme is that silicone pads are provided on the four inner walls of the water treatment chamber in contact with the electrolytic cell. The silicone pads are relatively thin, and opening holes will easily destroy the structure of the silicone pads and affect the sealing effect. Therefore, the water treatment chamber is connected to the water storage tank through the cathode current collecting plates on both sides and the openings on the anion exchange membrane.

[0014] Furthermore, openings are respectively provided at both ends of the flow channel at positions corresponding to the anode current collecting plate and the fitted electrolytic cell end plate to form a liquid inlet channel and a liquid outlet channel. The two ends of the liquid inlet channel are respectively connected to the liquid outlet end of the suspension circulation device and the flow channel, and the two ends of the liquid outlet channel are respectively connected to the flow channel and the liquid inlet end of the suspension circulation device.

[0015] The beneficial effect of adopting the above further solution is that the anode suspension can circulate in the flow channel.

[0016] Furthermore, the anode suspension includes activated carbon powder conductive agent, iron oxide, manganese oxide and conductive electrolyte solution.

[0017] The beneficial effect of adopting the above further scheme is that the activated carbon powder conductive agent can increase the conductivity of the anode suspension, manganese oxide can oxidize As(III) to reduce its toxicity, and iron oxide can adsorb As(V), thereby removing As(III) and As(V) from the sewage.

[0018] Further, the iron oxide may be at least one of goethite, lepidocrocite, hematite, magnetite and ferrihydrite, the manganese oxide may be birnessite, cryptomelane, calansite, pyrolusite, the electrolyte may be at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate and potassium sulfate, and the electrolyte may be at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate and potassium sulfate.

[0019] Furthermore, the proportion of activated carbon powder in the anode suspension is 3% to 9%, the proportion of iron oxide is 0.1% to 2%, the proportion of manganese oxide is 0.1% to 2%, and the proportion of electrolyte is 0.1% to 1%.

[0020] The beneficial effect of adopting the above further solution is that the anode suspension has both good fluidity and good electrical conductivity and an oxidative adsorption effect on arsenic.

[0021] Furthermore, the anode current collector is a carbon material electrode, a platinum electrode or a titanium electrode, and the cathode is a graphite electrode, an activated carbon electrode or a biochar electrode.

[0022] The present invention also provides a method for removing As(III) from sewage using the electrochemical device, comprising the following steps:

[0023] 1). The anode suspension is made to flow through the flow channel on the anode current collector through the suspension circulation device, and the sewage containing As(III) is made to flow through the water treatment chamber between the cathode current collector and the anion exchange membrane;

[0024] 2). Start the DC power supply and apply a voltage of 0.3~1.2V between the anode and the cathode for 20~120min.

[0025] The beneficial effects of the present invention are: good treatment effect on arsenic-containing wastewater, removal rates of As(III) and total arsenic in wastewater are as high as 98.6% and 94.7% respectively, and the method is simple, efficient and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The schematic diagram of the structure of the electrochemical device for removing As(III) from aqueous solution by self-alkalization of the present invention;

[0027] Figure 2 A schematic diagram of the structural decomposition of the electrochemical device for removing As(III) from aqueous solution by self-alkalization according to the present invention;

[0028] Figure 3 The As(III) and T-As removal rates and pH changes in the system in Example 1 of the present invention are shown in FIG. Figure 3 a is the removal rate of As(III) and T-As, Figure 3 b is the pH change curve in the system;

[0029] Figure 4 The As(III) and T-As removal rates and pH changes in the system in Example 2 of the present invention are shown in FIG. Figure 4 a is the removal rate of As(III) and T-As, Figure 4 b is the pH change curve in the system;

[0030] Figure 5 The As(III) and T-As removal rates and pH changes in the system in Example 3 of the present invention are shown in FIG. Figure 5 a is the removal rate of As(III) and T-As, Figure 5 b is the pH change curve in the system;

[0031] Figure 6 The As(III) and T-As removal rates and pH changes in the system in Example 4 of the present invention are shown in FIG. Figure 6 a is the removal rate of As(III) and T-As, Figure 6 b is the pH change curve in the system.

[0032] In the figure, 1. electrolytic cell end plate, 2. cathode current collecting plate, 3. water treatment chamber, 4. anion exchange membrane, 5. anode current collecting plate, 6. liquid storage tank, 7. water storage tank, 8. silicone gasket, and 9. flow channel. DETAILED DESCRIPTION

[0033] The principles and features of the present invention are described below in conjunction with the accompanying drawings and specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] The invention provides an electrochemical device for removing As(III) in an aqueous solution by self-alkalization. The device comprises a sealed electrolytic cell, an anion exchange membrane 4 arranged in the electrolytic cell, a cathode current collecting plate 2 and an anode current collecting plate 5 arranged on both sides of the anion exchange membrane 4, wherein the cathode current collecting plate 2 and the anode current collecting plate 5 are respectively connected to an external power source, the cathode current collecting plate 2 is a hydrogen peroxide generating electrode, after voltage is applied, dissolved oxygen is reduced on the surface to generate hydrogen peroxide, a water treatment chamber 3 is formed between the cathode current collecting plate 2 and the anion exchange membrane 4, the anode current collecting plate 5 is attached to the anion exchange membrane 4, and a flow channel 9 for anode suspension to flow is formed between the two, the flow channel 9 is etched on a side of the anode current collector close to the anion exchange membrane 4, the anode suspension is an electrolyte having an oxidative adsorption effect on As(III), and the electrochemical device further comprises a sewage circulation device and a suspension circulation device, the two ends of a pipeline of the sewage circulation device are respectively connected to the water treatment chamber 3, and the two ends of the suspension circulation device are respectively connected to the flow channel 9.

[0035] By applying voltage in the system, dissolved oxygen is electrochemically reduced to generate hydrogen peroxide on the surface of the cathode current collector 2, and at the same time, H 2 O dissociation produces H + Will promote OH − The two processes together promote the increase of pH value of the polluted aqueous solution, i.e., self-alkalization. The increase in pH directly leads to the dissociation of the electrically neutral As(III) into H 2 AsO 3− and HAsO 3 2− , and then can migrate to the flow channel 9 on the anode current collector 5 through the anion exchange membrane 4 under the action of the electric field force. In addition, the formed hydrogen peroxide can oxidize As(III) to As(V), and can also migrate to the flow channel 9 on the anode current collector 5. As(V) migrated to the flow channel 9 can be directly adsorbed by the anode suspension, and As(III) can be oxidized by the anode suspension to As(V) and finally adsorbed. The continuous self-alkalization electrochemical system formed by the present invention promotes the dissociation and oxidation of As(III), thereby significantly enhancing the removal effect of As(III).

[0036] Preferably, the sewage circulation device includes a water storage tank 7 and a constant flow pump, and the suspension circulation device includes a liquid storage tank 6 and a constant flow pump.

[0037] Preferably, the surfaces of the water treatment chamber 3 that contact the inner wall of the electrolytic cell are provided with a silicone gasket 8 , which can seal the water treatment chamber 3 .

[0038] Preferably, the cathode current collecting plate 2 and the anode current collecting plate 5 are respectively attached to the end plates of the adjacent electrolytic cells.

[0039] Preferably, the cathode current collecting plate 2 and the electrolytic cell end plate 1 are provided with openings at corresponding positions to form an inlet channel, and the two ends thereof are respectively connected to the outlet end of the sewage circulation device and the water treatment chamber 3, and the anion exchange membrane 4, the anode current collecting plate 5 and the electrolytic cell end plate 1 are provided with openings at corresponding positions to form an outlet channel, and the outlet channel does not pass through the flow channel 9, and the two ends of the outlet channel are respectively connected to the water treatment chamber 3 and the inlet end of the sewage circulation device. The sewage to be treated flows out of the water storage tank 7, flows to the water treatment chamber 3 through the inlet channel under the action of the constant current pump, and flows out through the outlet channel back to the water storage tank 7 after treatment, and performs the circulation treatment of the sewage.

[0040] Preferably, the connection points between the water inlet channel and the water outlet channel and the water treatment chamber 3 respectively constitute the water inlet and the water outlet of the water treatment chamber 3. The water inlet and the water outlet of the water treatment chamber 3 are respectively arranged on the diagonal lines of the water treatment chamber 3, which can increase the contact time between the sewage and the cathode and the anion exchange membrane 4, thereby improving the sewage treatment efficiency.

[0041] Since silicone pads are provided on the four inner walls of the water treatment chamber 3 in contact with the electrolytic cell, the silicone pads are relatively thin, and opening holes will easily destroy the structure of the silicone pads and affect the sealing effect. Therefore, the water treatment chamber 3 is connected to the water storage tank 7 through the holes in the cathode current collecting plates 2 on both sides and the anion exchange membrane 4.

[0042] Preferably, openings are respectively provided at both ends of the flow channel 9 at positions corresponding to the anode current collecting plate 5 and the adjacent electrolytic cell end plate 1 to form a liquid inlet channel and a liquid outlet channel. The two ends of the liquid inlet channel are respectively connected to the liquid outlet end of the suspension circulation device and the flow channel 9, and the two ends of the liquid outlet channel are respectively connected to the flow channel 9 and the liquid inlet end of the suspension circulation device. The anode suspension can circulate in the flow channel 9 under the action of a constant current pump.

[0043] Preferably, the electrochemical device further comprises fixing bolts for clamping the electrolytic cell end plate 1, the cathode current collecting plate 2, the water treatment chamber 3, the anion exchange membrane 4, the anode current collecting plate 5 and the other end plate of the electrolytic cell to ensure the sealing of the electrochemical device.

[0044] Preferably, the anode suspension includes an activated carbon powder conductive agent, iron oxide, manganese oxide and a conductive electrolyte solution. The activated carbon powder conductive agent can increase the conductivity of the anode suspension, the manganese oxide can oxidize As(III) to reduce its toxicity, and the iron oxide can adsorb As(V) to remove As(III) and As(V) in the sewage.

[0045] Preferably, the iron oxide may be at least one of goethite, lepidocrocite, hematite, magnetite, and ferrihydrite, the manganese oxide may be birnessite, cryptomelane, calansite, and pyrolusite, the electrolyte may be at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate, and the electrolyte may be at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate, and potassium sulfate.

[0046] Preferably, the ratio of activated carbon powder is 3-9%, the ratio of iron oxide in the suspension is 0.1-2%, the ratio of manganese oxide is 0.1-2%, and the ratio of electrolyte is 0.1-1%. Under this ratio, the anode suspension has good fluidity, good conductivity and oxidation adsorption effect on arsenic.

[0047] Preferably, the anode current collector is a carbon material electrode, a platinum electrode or a titanium electrode, and the cathode is a graphite electrode, an activated carbon electrode or a biochar electrode.

[0048] The present invention also provides a method for removing As(III) from sewage using the electrochemical device, comprising the following steps:

[0049] 1). The anode suspension flows through the flow channel 9 on the anode current collector 5 through the suspension circulation device, and the sewage containing As(III) flows through the water treatment chamber 3 between the cathode current collector 2 and the anion exchange membrane 4;

[0050] 2). Start the DC power supply and apply a voltage of 0.3~1.2V between the anode and the cathode for 20~120min.

[0051] Example 1

[0052] The electrochemical device and method of the present invention are used to treat As(III)-contaminated water, and the initial As(III) concentration is 151.3 μg / L −1 , including the following steps: injecting the sewage solution to be treated into the water treatment chamber 3 through a constant flow pump, the anode suspension in the flow channel 9 of the anode current collector 5 contains a mixture of 1% ferrihydrite and birnessite, 9% activated carbon powder and 0.5% NaCl, the anode and cathode are both graphite plates, but the surface of the anode current collector 5 is etched with a flow channel 9 for the flow of the anode suspension. Then turn on the power supply, control the voltage between the anode and the cathode to be 1.2V, treat for 120min, take samples at regular intervals during the treatment process to determine the concentrations of As(III) and total arsenic (T-As) in the liquid to be treated, and record the pH change, through Figure 3 It can be seen that in this embodiment, the system pH rises to a maximum of 10.9, and the corresponding As(III) and T-As removal rates are as high as 98.6% and 94.7%, respectively.

[0053] Example 2

[0054] The electrochemical device and method of the present invention are used to treat As(III)-contaminated water, and the initial As(III) concentration is 151.3 μg / L −1 , including the following steps: injecting the sewage solution to be treated into the water treatment chamber 3 through a constant flow pump, the anode suspension in the flow channel 9 of the anode current collector 5 contains a mixture of 1% ferrihydrite and birnessite, 9% activated carbon powder and 0.5% NaCl, the anode and cathode are both graphite plates, but the anode surface is etched with a flow channel 9 for the flow of the anode suspension. Then turn on the power supply, control the voltage between the anode and the cathode to be 0.6V, treat for 120 minutes, take samples at regular intervals during the treatment process to determine the concentrations of As(III) and total arsenic (T-As) in the liquid to be treated, and record the pH change, through Figure 4 It can be seen that in this embodiment, the system pH rises to a maximum of 10.4, and the corresponding As(III) and T-As removal rates are as high as 95.4% and 87.2%, respectively.

[0055] Comparative Example 1

[0056] The electrochemical device and method of the present invention are used to treat As(III)-contaminated water, and the initial As(III) concentration is 151.3 μg / L −1, including the following steps: injecting the sewage solution to be treated into the water treatment chamber 3 through a constant flow pump, the anode suspension in the flow channel 9 of the anode current collector 5 contains a mixture of 1% ferrihydrite and birnessite, 9% activated carbon powder and 0.5% NaCl, the anode and cathode are both graphite plates, but the anode surface is etched with a flow channel 9 for the anode suspension to flow. Then, the power supply is not turned on, and the treatment is carried out for 120 minutes. During the treatment process, sampling is performed at regular intervals to determine the concentrations of As(III) and total arsenic (T-As) in the treated solution, and the pH changes are recorded. Figure 5 It can be seen that in this comparative example, the pH of the system did not change significantly, and the corresponding As(III) and T-As removal rates were 2.1% and 2.1%, respectively.

[0057] Comparative Example 2

[0058] The electrochemical device and method of the present invention are used to treat As(III)-contaminated water, and the initial As(III) concentration is 151.3 μg / L −1 , including the following steps: injecting the sewage solution to be treated into the water treatment chamber 3 through a constant flow pump, the anode and cathode are both fixed graphite plates, and do not contain a flow channel 9 for the flow of the anode suspension. Then turn on the power supply, control the voltage between the anode and the cathode to be 1.2V, treat for 120min, and take samples at regular intervals during the treatment process to determine the concentrations of As(III) and total arsenic (T-As) in the treated liquid, and record the pH changes. Figure 6 It can be seen that in this comparative example, the system pH rose to a maximum of 8.3, and the corresponding As(III) and T-As removal rates were 38.3% and 9.2%, respectively.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An electrochemical device for removing As(III) from aqueous solution by self-alkalization, It is characterized in that The invention comprises a sealed electrolytic cell, an anion exchange membrane (4) arranged in the electrolytic cell, a cathode current collecting plate (2) and an anode current collecting plate (5) arranged on both sides of the anion exchange membrane (4), the cathode current collecting plate (2) and the anode current collecting plate (5) being respectively connected to an external power source, characterized in that the cathode current collecting plate (2) is a hydrogen peroxide generating electrode, and a water treatment chamber (3) is formed between the cathode current collecting plate (2) and the anion exchange membrane (4), the anode current collecting plate (5) is bonded to the anion exchange membrane (4), and a flow channel (9) for anode suspension liquid to flow is formed between the two, the flow channel (9) is etched on a side of the anode current collecting plate (5) close to the anion exchange membrane (4), the anode suspension liquid is an electrolyte having an oxidative adsorption effect on As(III), and further comprises a sewage circulation device and a suspension liquid circulation device, the two ends of the pipeline of the sewage circulation device are respectively connected to the water treatment chamber (3), and the two ends of the suspension liquid circulation device are respectively connected to the flow channel; The cathode current collecting plate (2) and the anode current collecting plate (5) are respectively attached to adjacent electrolytic cell end plates (1); The cathode current collecting plate (2) and the electrolytic cell end plate (1) attached thereto have openings at corresponding positions to form a water inlet channel, and the two ends of the water inlet channel are respectively connected to the water outlet of the sewage circulation device and the water treatment chamber (3), and the anion exchange membrane (4), the anode current collecting plate (5) and the electrolytic cell end plate (1) attached thereto have openings at corresponding positions to form a water outlet channel, and the water outlet channel does not pass through the flow channel, and the two ends of the water outlet channel are respectively connected to the water treatment chamber (3) and the water inlet of the sewage circulation device; The anode suspension comprises an activated carbon powder conductive agent, iron oxide, manganese oxide and a conductive electrolyte solution.

2. The electrochemical device for removing As(III) from aqueous solution by self-alkalization according to claim 1, It is characterized in that The surfaces of the water treatment chamber (3) in contact with the inner wall of the electrolytic cell are provided with silica gel gaskets (8).

3. The electrochemical device for removing As(III) from aqueous solution by self-alkalization according to claim 1, It is characterized in that Openings are respectively provided at both ends of the flow channel at positions corresponding to the anode current collecting plate (5) and the fitted electrolytic cell end plate (1), forming a liquid inlet channel and a liquid outlet channel; both ends of the liquid inlet channel are respectively connected to the liquid outlet end of the suspension circulation device and the flow channel; and both ends of the liquid outlet channel are respectively connected to the flow channel and the liquid inlet end of the suspension circulation device.

4. The electrochemical device for removing As(III) from aqueous solution by self-alkalization according to claim 1, It is characterized in that The iron oxide is at least one of goethite, lepidocrocite, hematite, magnetite and ferrihydrite, the manganese oxide is at least one of birnessite, cryptomelane, calansite and pyrolusite, and the electrolyte is at least one of sodium chloride, potassium chloride, sodium nitrate, potassium nitrate, sodium sulfate and potassium sulfate.

5. The electrochemical device for removing As(III) from aqueous solution by self-alkalization according to claim 1, It is characterized in that The proportion of activated carbon powder in the anode suspension is 3-9%, the proportion of iron oxide is 0.1-2%, the proportion of manganese oxide is 0.1-2%, and the proportion of electrolyte is 0.1-1%.

6. The electrochemical device for removing As(III) from aqueous solution by self-alkalization according to any one of claims 1 to 5, It is characterized in that The anode current collecting plate (5) is a carbon material electrode, a platinum electrode or a titanium electrode, and the cathode current collecting plate (2) is a graphite electrode, an activated carbon electrode or a biochar electrode.

7. A method for removing As(III) from sewage using the electrochemical device for removing As(III) from aqueous solution by self-alkalization as described in any one of claims 1 to 6, It is characterized in that The following steps are involved: 1). The anode suspension is made to flow through the flow channel (9) on the anode current collecting plate (5) through the suspension circulation device, and the sewage containing As(III) is made to flow through the water treatment chamber (3) between the cathode current collecting plate (2) and the anion exchange membrane (4); 2). Start the DC power supply and apply a voltage of 0.3~1.2V between the anode and the cathode for 20~120min.

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