A device for treating high-salinity organic wastewater by using a bipolar membrane electrodialysis

Abstract

The application discloses a device for treating high-salt organic wastewater by using a bipolar membrane electrodialysis, which comprises a membrane stack, a direct-current power supply and a circulating pipeline system. The membrane stack is provided with one anode plate and one cathode plate on two sides respectively, and is assembled by a bipolar membrane, a cation exchange membrane and an anion exchange membrane. The inside of the membrane stack is composed of an anode reaction compartment, an acid liquid compartment, a feed liquid desalination compartment, an alkali liquid compartment and a cathode reaction compartment. The bipolar membrane, the acid liquid compartment, the anion exchange membrane, the feed liquid desalination compartment, the cation exchange membrane and the alkali liquid compartment can form one or more repeating units in sequence. The feed liquid circulating pipeline is communicated with the anode reaction compartment, the feed liquid desalination compartment and the cathode reaction compartment respectively, the acid liquid circulating pipeline is communicated with the acid liquid compartment, and the alkali liquid circulating pipeline is communicated with the alkali liquid compartment. The device has a simplified structure and a low operation cost, can realize desalination, organic pollutant degradation and acid-alkali recovery simultaneously, and is especially suitable for treating medium and low COD high-salt organic wastewater.

Description

Technical Field

[0001] This invention relates to the field of high-salt organic wastewater treatment and resource utilization technology, and particularly to a non-polar bipolar membrane electrodialysis treatment device for high-salt organic wastewater. Background Technology

[0002] High-salinity organic wastewater is widely generated in industrial processes such as petrochemicals, fine chemicals, pharmaceuticals, and flue gas desulfurization. This type of wastewater is typically characterized by high salt concentration, poor biodegradability, and difficulty in treatment. While evaporation and crystallization can remove salt in existing treatment methods, they generally suffer from high energy consumption, high operating costs, and difficulties in subsequent salt disposal. Conventional biological treatments are easily inhibited by high-salinity environments, leading to decreased microbial activity, reduced treatment efficiency, and in severe cases, even instability of the biological system. Furthermore, residual recalcitrant organic matter in the wastewater further weakens the effectiveness of biological treatment. Therefore, developing a highly efficient treatment device capable of simultaneously achieving desalination, organic pollutant degradation, and resource recovery is of great significance.

[0003] Bipolar membrane electrodialysis technology can generate H+ through the water dissociation reaction at the bipolar membrane interface under the action of an applied DC electric field. + and OH - This process drives the migration of anions and cations in the wastewater to their respective compartments, thereby achieving the directional conversion of salts into acids and alkalis. It shows promising application prospects in the resource recovery treatment of high-salinity wastewater. Currently, the common practice for treating high-salinity organic wastewater using bipolar membrane electrodialysis involves a series of pretreatments to remove organic matter before the wastewater enters the bipolar membrane device for desalination. For example, patent publication number CN115650524A proposes a desulfurization wastewater resource recovery system that combines advanced oxidation pretreatment, nanofiltration, and bipolar membrane electrodialysis in series. The degradation of organic pollutants mainly relies on the front-end pretreatment. In bipolar membrane electrodialysis devices, the electrodes only provide an electric field, failing to fully utilize their potential for electrolytic degradation of organic pollutants. Therefore, it is necessary to develop a bipolar membrane electrodialysis treatment device with a simpler structure that can simultaneously achieve desalination, organic pollutant degradation, and acid / alkali recovery. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of the prior art mentioned above, and to provide a non-polar bipolar membrane electrodialysis treatment device for high-salt organic wastewater, which can simultaneously achieve desalination of high-salt organic wastewater, degradation of organic pollutants and resource recovery of acid and alkali, and reduce the operating cost of the device.

[0005] The technical solution adopted in this invention is: a non-polar bipolar membrane electrodialysis treatment device for high-salt organic wastewater, comprising a power supply, a membrane stack, and a circulation pipeline; The membrane stack is composed of an anode plate, an anode reaction chamber, a bipolar membrane I, an acid solution chamber, an anion exchange membrane, a feed desalination chamber, a cation exchange membrane, an alkali solution chamber, a bipolar membrane II, a cathode reaction chamber, and a cathode plate assembled sequentially. The membrane stack has only one anode plate and one cathode plate on each side. The bipolar membrane, acid solution compartment, anion exchange membrane, feed desalination compartment, cation exchange membrane and alkali solution compartment are arranged in sequence to form one or more repeating units. No electrodes are set in the repeating units. The power supply is a DC power supply, with its positive terminal connected to the anode plate and its negative terminal connected to the cathode plate; The circulation pipeline includes three independent circulation loops: a liquid circulation pipeline, an alkali circulation pipeline, and an acid circulation pipeline; the liquid circulation pipeline includes a liquid tank, a liquid circulation pump, and a liquid pipeline; the alkali circulation pipeline includes an alkali tank, an alkali circulation pump, and an alkali pipeline; the acid circulation pipeline includes an acid tank, an acid circulation pump, and an acid pipeline. The feed liquid circulation pipeline is connected to the anode reaction chamber, the feed liquid desalination chamber and the cathode reaction chamber respectively, so that the high-salt organic wastewater to be treated can be used as both electrode working liquid and desalination treatment liquid, thereby eliminating the need for an independent electrode liquid circulation system. The acid circulation pipeline is connected to the acid compartment, and the alkali circulation pipeline is connected to the alkali compartment.

[0006] Furthermore, the anode plate is a titanium-based metal oxide coated electrode, and the cathode plate is one of a stainless steel electrode, a titanium electrode, or a nickel-based electrode.

[0007] Furthermore, the anion exchange membrane and the cation exchange membrane are homogeneous or heterogeneous ion exchange membranes.

[0008] Furthermore, the bipolar membrane one and bipolar membrane two are capable of water dissociation and generating H under the action of a DC electric field. + and OH - The bipolar membrane; the anion exchange membrane is an anion-selective permeable membrane, and the cation exchange membrane is a cation-selective permeable membrane.

[0009] Furthermore, the power supply is a constant current source or a constant voltage source, with an operating current density range of 0 mA / cm². 2 ~120 mA / cm 2 .

[0010] The device described in this invention is used to treat high-salt organic wastewater, which refers to industrial high-salt organic wastewater such as flue gas desulfurization wastewater, printing and dyeing wastewater, petrochemical wastewater, fine chemical wastewater, and pharmaceutical wastewater, preferably medium-low COD high-salt organic wastewater.

[0011] In this invention, the feed liquid only enters the feed liquid circulation pipeline and flows through the anode reaction chamber, the feed liquid desalination chamber, and the cathode reaction chamber respectively, so that the high-salt organic wastewater to be treated can also serve as the electrode working solution and the desalination treatment solution; the alkali solution only enters the alkali solution circulation pipeline and flows through the alkali solution chamber; the acid solution only enters the acid solution circulation pipeline and flows through the acid solution chamber.

[0012] The reaction principle of the electrodeless bipolar membrane electrodialysis device: Under the influence of an applied DC electric field, the feed solution in the anolyte chamber undergoes an electrochemical oxidation reaction on the anode surface, generating reactive species such as hydroxyl radicals (•OH) and promoting the oxidative degradation of organic pollutants; an electrochemical reduction reaction occurs in the cathode chamber. Simultaneously, the bipolar membrane undergoes a water dissociation reaction under the influence of the electric field, producing H₂. + and OH - Anions in the feed solution desalination chamber migrate through the anion exchange membrane to the acid solution compartment and react with H+. + The cations in the feed solution desalination chamber migrate through the cation exchange membrane to the alkali solution compartment and react with OH- to form the corresponding acid; - The corresponding bases are formed by combining; the main reaction can be represented as follows: Anode reaction compartment: H2O-e - →•OH+H + ;RH+•OH→R•+ H2O; Cathode reaction compartment: 2H₂O + 2e⁻ - →2OH - +H2; Desalination chamber: MX→M n+ +X m- Acid compartment: H + +X m- →H m X; Alkali compartment: M n+ +OH - →M(OH) n .

[0013] The beneficial effects of this invention are: (1) This invention achieves the directional conversion of salt in the feed solution into acid and alkali products through the synergistic effect of bipolar membrane, anion exchange membrane and cation exchange membrane, thereby realizing the desalination of high-salt organic wastewater and the recovery of salt resources.

[0014] (2) In this invention, the feed liquid flows through the anode reaction chamber, the feed liquid desalination chamber and the cathode reaction chamber at the same time, which can promote the degradation of organic pollutants, improve the biodegradability of wastewater and reduce the impact of organic matter migration on the purity of acid and alkali products.

[0015] (3) Under the premise of eliminating the independent electrode liquid circulation system, the present invention only sets one positive electrode plate and one negative electrode plate on each side, which simplifies the structure, reduces the operating cost, and can simultaneously achieve desalination, degradation of organic pollutants and recycling of acid and alkali resources. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the electrodeless bipolar membrane electrodialysis device of the present invention; Figure 2 This is a schematic diagram of the membrane stack structure and water inlet method of the present invention; In the diagram: 1-Power supply, 2-Membrane stack, 3-Circulation pipeline, 4-Feed tank, 5-Feed circulation pump, 6-Feed pipeline, 7-Alkali tank, 8-Alkali circulation pump, 9-Alkali pipeline, 10-Acid tank, 11-Acid circulation pump, 12-Acid pipeline, 13-Anode plate, 14-Anode reaction compartment, 15-Bipolar membrane one, 16-Acid compartment, 17-Anion exchange membrane, 18-Feed desalination compartment, 19-Cation exchange membrane, 20-Alkali compartment, 21-Bipolar membrane two, 22-Cathode reaction compartment, 23-Cathode plate. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1-2 As shown, the power supply 1 is a constant current source or a constant voltage source, with an operating current density range of 0 mA / cm². 2 ~120mA / cm 2 Its positive electrode is connected to the anode plate 13, and its negative electrode is connected to the cathode plate 23; the left side of the membrane stack 2 is the anode plate 13, and the right side is the cathode plate 23; between the anode plate 13 and the cathode plate 23, from left to right, are the anode reaction chamber 14, bipolar membrane 15, acid solution chamber 16, anion exchange membrane 17, feed desalination chamber 18, cation exchange membrane 19, alkali solution chamber 20, bipolar membrane 21, and cathode reaction chamber 22, wherein the bipolar membrane 15, acid solution chamber 16, and anion exchange membrane 17 are... The feed desalination chamber 18, cation exchange membrane 19, alkali compartment 20, and bipolar membrane 21 can be equipped with repeating units as needed; the circulation pipeline 3 includes three independent circulation loops: feed circulation pipeline, alkali circulation pipeline, and acid circulation pipeline; the feed circulation pipeline includes feed tank 4, feed circulation pump 5, and feed pipeline 6; the alkali circulation pipeline includes alkali tank 7, alkali circulation pump 8, and alkali pipeline 9; the acid circulation pipeline includes acid tank 10, acid circulation pump 11, and acid pipeline 12.

[0019] The anode plate 13 is a titanium-based metal oxide coated electrode, and the cathode plate 23 is one of a stainless steel electrode, a titanium electrode, or a nickel-based electrode. The feed liquid only enters the feed liquid circulation pipeline and flows through the anode reaction chamber 14, the feed liquid desalination chamber 18, and the cathode reaction chamber 22, respectively, so that the high-salt organic wastewater to be treated serves as both the electrode working liquid and the desalination treatment liquid. The alkali solution only enters the alkali solution circulation pipeline and flows through the alkali solution chamber 20. The acid solution only enters the acid solution circulation pipeline and flows through the acid solution chamber 16.

[0020] Specifically, the high-salt organic wastewater stored in the feed tank 4 enters the anode reaction chamber 14, feed desalination chamber 18, and cathode reaction chamber 22 of the membrane stack 2 via the feed circulation pump 5 and feed pipeline 6; the alkali solution stored in the alkali tank 7 enters the alkali solution chamber 20 of the membrane stack 2 via the alkali solution circulation pump 8 and alkali solution pipeline 9; the acid solution stored in the acid tank 10 enters the acid solution chamber 16 of the membrane stack 2 via the acid solution circulation pump 11 and acid solution pipeline 12. The positive terminal of the power supply 1 is connected to the anode plate 13, and the negative terminal is connected to the cathode plate 23. Under the action of the applied electric field, the anions in the feed desalination chamber 18 migrate to the acid solution chamber 16 through the anion exchange membrane 17 and react with the H+ generated by the hydrolysis of the bipolar membrane 15. + The cations in the feed solution desalination chamber 18 migrate through the cation exchange membrane 19 to the alkali solution compartment 20, and react with the OH- produced by the hydrolysis of the bipolar membrane 21. - The reaction forms a corresponding alkali. Simultaneously, an electrochemical oxidation reaction occurs in the anode reaction chamber 14, promoting the degradation of organic pollutants in the feed solution, while an electrochemical reduction reaction occurs in the cathode reaction chamber 22. After treatment by the membrane stack 2, the effluent from the anode reaction chamber 14, the feed solution desalination chamber 18, and the cathode reaction chamber 22 is returned to the feed solution tank 4 via the feed solution pipeline 6, completing the feed solution treatment cycle; the alkali solution generated in the alkali solution chamber 20 is returned to the alkali solution tank 7 via the alkali solution pipeline 9, completing the alkali solution concentration cycle; the acid solution generated in the acid solution chamber 16 is returned to the acid solution tank 10 via the acid solution pipeline 12, completing the acid solution concentration cycle; this cycle repeats continuously to achieve desalination of high-salt organic wastewater, degradation of organic pollutants, and resource recovery of acids and alkalis.

[0021] Using Example 1, the above-mentioned bipolar membrane electrodialysis device with a non-polar chamber was employed: the feed tank 4 contained 1000 mL of flue gas desulfurization wastewater with a COD content of 68.42 mg / L and a Na2SO4 content of 28.36 g / L, which was circulated separately. The alkali solution in the alkali compartment contained 1000 mL of pure water, which was circulated separately. The acid solution in the acid compartment contained 1000 mL of pure water, which was circulated separately. The setup was characterized by 2 repeat units, pH 7, and a current density of 30 mA / cm². 2Under these conditions, after 140 min of treatment, the desalination rate was 97.51%, the COD degradation rate was 42.85%, the NaOH concentration recovered in the alkali compartment was 0.38 mol / L, and the H2SO4 concentration recovered in the acid compartment was 0.19 mol / L.

[0022] Using Example 2, the above-mentioned electrodeless bipolar membrane electrodialysis device was employed: the feed tank 4 contained 1000 mL of flue gas desulfurization wastewater with a COD content of 82.10 mg / L and a Na2SO4 content of 25.77 g / L, which was circulated separately. The alkali solution in the compartment contained 1000 mL of pure water, which was circulated separately. The acid solution in the compartment contained 1000 mL of pure water, which was circulated separately. The setup was as follows: 2 repeat units, pH 7, and current density 50 mA / cm². 2 Under these conditions, after 90 minutes of treatment, the desalination rate was 96.94%, the COD degradation rate was 49.76%, the NaOH concentration recovered in the alkali compartment was 0.36 mol / L, and the H2SO4 concentration recovered in the acid compartment was 0.17 mol / L.

[0023] Using Example 3, the above-mentioned bipolar membrane electrodialysis device with a non-polar chamber was employed: the feed tank 4 contained 1000 mL of flue gas desulfurization wastewater with a COD content of 61.53 mg / L and a Na2SO4 content of 22.84 g / L, which was circulated separately. The alkali solution in the compartment contained 1000 mL of pure water, which was circulated separately. The acid solution in the compartment contained 1000 mL of pure water, which was circulated separately. The setup was characterized by 2 repeat units, pH 7, and a current density of 70 mA / cm². 2 Under these conditions, after 65 minutes of treatment, the desalination rate was 96.67%, the COD degradation rate was 49.36%, the concentration of NaOH recovered in the alkali compartment was 0.31 mol / L, and the concentration of H2SO4 recovered in the acid compartment was 0.15 mol / L.

[0024] Using Example 4, the above-mentioned bipolar membrane electrodialysis device with a non-polar chamber was employed: the feed tank 4 contained 1000 mL of flue gas desulfurization wastewater with a COD content of 86.47 mg / L and a Na2SO4 content of 27.18 g / L, which was circulated separately. The alkali solution in the compartment contained 1000 mL of pure water, which was circulated separately. The acid solution in the compartment contained 1000 mL of pure water, which was circulated separately. The setup was as follows: 2 repeat units, pH 5, and current density 50 mA / cm². 2Under these conditions, after 90 minutes of treatment, the desalination rate was 97.66%, the COD degradation rate was 50.23%, the NaOH concentration recovered in the alkali compartment was 0.37 mol / L, and the H2SO4 concentration recovered in the acid compartment was 0.18 mol / L.

[0025] Using Example 5, the above-mentioned bipolar membrane electrodialysis device with a non-polar chamber was employed: the feed tank 4 contained 1000 mL of flue gas desulfurization wastewater with a COD content of 57.26 mg / L and a Na2SO4 content of 21.96 g / L, which was circulated separately. The alkali solution in the alkali compartment contained 1000 mL of pure water, which was circulated separately. The acid solution in the acid compartment contained 1000 mL of pure water, which was circulated separately. The setup was characterized by 2 repeat units, pH 10, and a current density of 50 mA / cm². 2 Under these conditions, after 80 minutes of treatment, the desalination rate was 97.72%, the COD degradation rate was 43.29%, the NaOH concentration recovered in the alkali compartment was 0.30 mol / L, and the H2SO4 concentration recovered in the acid compartment was 0.15 mol / L.

[0026] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the guidance of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A non-polarized bipolar membrane electrodialysis treatment device for high-salt organic wastewater, characterized in that: It includes a power source (1), a membrane stack (2), and a circulation pipeline (3); The membrane stack (2) is composed of an anode plate (13), an anode reaction chamber (14), a bipolar membrane one (15), an acid solution chamber (16), an anion exchange membrane (17), a feed desalination chamber (18), a cation exchange membrane (19), an alkali solution chamber (20), a bipolar membrane two (21), a cathode reaction chamber (22), and a cathode plate (23) assembled sequentially. The membrane stack (2) has only one anode plate (13) and one cathode plate (23) on each side. The bipolar membrane (15), acid solution compartment (16), anion exchange membrane (17), feed desalination compartment (18), cation exchange membrane (19) and alkali solution compartment (20) are arranged in sequence to form one or more repeating units. No electrodes are set in the repeating units. The power supply (1) is a DC power supply, with its positive terminal connected to the anode plate (13) and its negative terminal connected to the cathode plate (23). The circulation pipeline (3) includes three independent circulation loops: a liquid circulation pipeline, an alkali circulation pipeline, and an acid circulation pipeline; the liquid circulation pipeline includes a liquid tank (4), a liquid circulation pump (5), and a liquid pipeline (6); the alkali circulation pipeline includes an alkali tank (7), an alkali circulation pump (8), and an alkali pipeline (9); the acid circulation pipeline includes an acid tank (10), an acid circulation pump (11), and an acid pipeline (12). The feed liquid circulation pipeline is connected to the anode reaction chamber (14), the feed liquid desalination chamber (18), and the cathode reaction chamber (22), respectively; The acid circulation pipeline is connected to the acid compartment (16), and the alkali circulation pipeline is connected to the alkali compartment (20).

2. The electrodeless bipolar membrane electrodialysis treatment device for high-salt organic wastewater according to claim 1, characterized in that: The anode plate (13) is a titanium-based metal oxide coated electrode, and the cathode plate (23) is one of a stainless steel electrode, a titanium electrode, or a nickel-based electrode.

3. The electrodeless bipolar membrane electrodialysis treatment device for high-salt organic wastewater according to claim 2, characterized in that: The anion exchange membrane (17) and the cation exchange membrane (19) are homogeneous or heterogeneous ion exchange membranes.

4. The electrodeless bipolar membrane electrodialysis treatment device for high-salt organic wastewater according to claim 3, characterized in that: The bipolar membrane one (15) and bipolar membrane two (21) are designed to achieve water dissociation and generate H under the action of a DC electric field. + and OH - The bipolar membrane; the anion exchange membrane (17) is an anion-selective permeable membrane, and the cation exchange membrane (19) is a cation-selective permeable membrane.

5. The electrodeless bipolar membrane electrodialysis treatment device for high-salt organic wastewater according to claim 4, characterized in that: The power supply (1) is a constant current source or a constant voltage source, with an operating current density range of 0 mA / cm². 2 ~120 mA / cm 2 .

Images