A method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system

Abstract

This invention discloses a method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system, belonging to the field of electrochemical technology. The invention uses activated carbon as a carrier, loading nickel-manganese bimetallic hydroxide (NiMn-LDH) onto the activated carbon surface, guiding and controlling its formation of a layered morphological structure. This overcomes the defect that NiMn-LDH cannot be directly used as a three-dimensional electrode for electrolysis due to its weak conductivity, thus producing a NiMn-LDH@C composite material with good specific surface area and electrochemical performance. This NiMn-LDH@C composite material is then used as a particle electrode filling the spaces between electrodes in a three-dimensional electrochemical reactor, forming a three-dimensional electrode system. This three-dimensional electrode system can improve the reaction rate of the electrocatalytic process, promote the generation of hydroxyl radicals, enhance the overall performance of the filler between electrodes, and demonstrates good performance in improving the degradation efficiency of halogenated disinfection byproducts in water.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system. Background Technology

[0002] Water disinfection is a crucial part of water treatment. Currently, chlorination is widely used in water treatment. During the disinfection process, disinfectants (i.e., chlorination and chlorination) react with naturally occurring organic matter (NOM) in the water to generate disinfection byproducts (DBPs), which have a significant impact on human health. Nitrogen-containing DBPs (N-DBPs), especially the emerging haloacetamides (HAcAms), exhibit higher cytotoxicity and genotoxicity than other N-DBPs. In mammalian cell assays, they were found to have 142× cytotoxicity and 12× genotoxicity higher than currently regulated haloacetic acids (HAAs). Dichloroacetamide (DCAcAm) is the most abundant type of HAcAms formed in chlorinated and ammonia-containing water, with the highest concentration reaching 5.6 μg / L. -1 Therefore, research on controlling the content of halogenated disinfection byproducts in water is crucial.

[0003] Electrochemical advanced oxidation (EAOP), as a type of advanced oxidation, plays a crucial role in wastewater treatment. EAOPs offer advantages such as thorough degradation, environmental friendliness, mild reaction conditions, controllable conditions, simple operation, adjustable parameters, resource recyclability, and sustainable application. Furthermore, the electrode and catalytic materials in the two-dimensional electrode can generate superoxide radicals (·O₂). 2- Electrochemicals utilize reactive groups such as hydroxyl radicals (·OH) to degrade pollutants in water. However, traditional two-dimensional electrodes suffer from drawbacks such as large mass transfer distances and high energy consumption, resulting in low reaction efficiency. Three-dimensional electrochemical (3D-E) processes can be achieved by filling the spaces between two-dimensional (2D) electrodes in conventional electrochemical systems with catalyst materials. Compared to traditional two-dimensional electrochemical systems, three-dimensional electrodes shorten the distance between reactants and electrodes, enhancing the system's conductivity and mass transfer performance. The catalyst material in the three-dimensional electrode is a crucial factor affecting its conductivity and catalytic performance.

[0004] Layered metal double hydroxides (LDHs) have become a viable option due to their excellent electrocatalytic performance, environmental friendliness, and low cost. LDH is a layered mixed hydroxide in which the positively charged primary layer undergoes anion exchange chemistry, with interlayer hydrated anions positioned above / below the charge centers of divalent and trivalent cations to balance the positive primary charge. Among various hydrotalcites, NiMn-LDH stands out due to its high Mn content. 3+ with Ni 2+The heterogeneous combination of these elements gives them a unique position in electrocatalysis. Furthermore, they possess advantages such as fast electron transport, large active surface area, high catalytic activity, and good morphology. However, NiMn-LDH has weak conductivity and cannot be directly used as a three-dimensional electrode in electrolysis. Activated carbon, on the other hand, is a material with good conductivity and excellent electrochemical performance.

[0005] Therefore, constructing a three-dimensional electrode system with excellent performance by combining NiMn-LDH with activated carbon, and innovating a method for efficiently removing halogenated disinfection byproducts from water through electrocatalysis, has significant implications and effects in the field of electrochemical catalysis technology.

[0006] Utility model with publication number CN208378503U discloses an electrochemical system for purifying drinking water. In this utility model, the anode and cathode are completely separated by a diaphragm and different materials are used, which optimizes the electrolyte environment and greatly improves the electrolysis efficiency. However, the chloride ions in the anolyte filled in the anode chamber of this utility model solve the technical problem of the easy deactivation of active metal materials in the traditional drinking water purification process. Utility model with publication number CN209259762U discloses a bioelectrochemical coupling system for purifying drinking water. The purified water from the first-stage bioelectrochemical system enters the second-stage bioelectrochemical system. After purification by the second-stage bioelectrochemical system, the purified water is directly used through an ultrafiltration membrane column or stored in a pressure storage tank for later use. The two-stage system uses a circulation pump and a return pipeline to return the purified effluent from the second-stage bioelectrochemical system to the first-stage bioelectrochemical system. After purification, the effluent then enters the second-stage bioelectrochemical system. The anode of the first-stage bioelectrochemical system is a three-dimensional electrode constructed from graphite sheets, graphite felt, amorphous carbon fibers, or activated carbon particles. Therefore, the scheme of layered bimetallic hydroxide catalyzing hydrogen peroxide to generate superoxide radicals and hydroxyl radicals was not disclosed. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention combines NiMn-LDH with activated carbon to construct a three-dimensional electrode system of NiMn-LDH@C particle electrode material with excellent performance. This three-dimensional electrode system is used to achieve electrocatalytic degradation of halogenated disinfection byproducts.

[0008] The technical solution of the present invention is as follows:

[0009] One objective of this invention is to provide a method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system. The method involves placing a nickel-manganese bimetallic hydroxide / activated carbon composite material (NiMn-LDH@C) in a three-dimensional electrochemical reactor as a particle electrode to form a three-dimensional electrode system. Under conditions of electro-aeration, the three-dimensional electrode system is used to perform electrochemical catalytic oxidation on water containing halogenated disinfection byproducts.

[0010] Furthermore, the nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn LDH@C is synthesized by the following steps:

[0011] S1. Take nickel nitrate hexahydrate and manganese nitrate tetrahydrate and dissolve them completely in deionized water, then take activated carbon and put it into the mixed solution and stir evenly.

[0012] S2. Ammonia water is added dropwise to a mixed solution containing activated carbon, and the reaction is completed. The deposited solid is then ground to obtain the nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn. LDH@C.

[0013] Furthermore, the molar ratio of nickel nitrate hexahydrate to manganese nitrate tetrahydrate in S1 is 2:1.

[0014] Furthermore, the Ni in the S1 mixed solution 2+ The molar concentration of Mn is 0.008-0.012 mol / L. 2+ The molar concentration is 0.004-0.006 mol / L.

[0015] Furthermore, the molar concentration of activated carbon added in S1 is 0.015-0.018 mol / L.

[0016] Furthermore, the molar concentration of ammonia in S2 is 0.8-1.2 mol / L.

[0017] Furthermore, the working electrode in the three-dimensional electrode system is made of graphite carbon plate.

[0018] Furthermore, the electrolyte in the three-dimensional electrode system is anhydrous sodium sulfate.

[0019] Furthermore, the electrolyte concentration is 24-26 g / L.

[0020] Furthermore, the energizing current density is 6.35-7.15 mA / cm². 2 .

[0021] Furthermore, the aeration rate is 0.5-1.5 L / min.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention is the first to propose using nickel-manganese bimetallic hydroxide / activated carbon material as a particle electrode material for the electrocatalytic degradation of halogenated disinfection byproducts. Using activated carbon as a carrier, nickel-manganese bimetallic hydroxide (NiMn-LDH) is loaded onto the activated carbon surface, guiding and controlling its layered morphological structure. This overcomes the defect that NiMn-LDH cannot be directly used as a three-dimensional electrode in electrolysis due to its weak conductivity, thus producing a nickel-manganese bimetallic hydroxide / activated carbon composite material (NiMn-LDH@C) with good specific surface area and electrochemical performance. Electrochemical experiments showed that the particle electrode material of this invention, at a mass of 4.4 g and a current density of 6.75 mA / cm², achieved good electrochemical performance. 2 When the electrolyte concentration was 25 g / L and the initial pollutant concentration was 10.5 mg / L, the removal rate of dichloroacetamide by the three-dimensional electrode system remained stable at 68.5% after 90 min of electrolysis, demonstrating the excellent electrocatalytic performance of the electrode material prepared in this invention.

[0024] 2. Compared with traditional two-dimensional electrodes, the three-dimensional electrode system disclosed in this invention has a larger contact area, higher efficiency, and low energy consumption. The device only requires setting the voltage, using electrical energy as the excitation energy (pulse power supply), and inorganic matter as the initiator. It utilizes O2 in the air to generate H2O2 through a chemical reaction. Further decomposition of H2O2 generates ·OH, and through addition, substitution, electron transfer, and bond breaking reactions between free radicals and organic compounds, the large, recalcitrant organic molecules of halogenated disinfection byproducts in the water are oxidized and degraded into low-toxicity or non-toxic small molecules, or even directly degraded into CO2 and H2O, approaching complete mineralization, thus ensuring water quality safety. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the NiMn-LDH@C nickel-manganese bimetallic hydroxide / activated carbon composite material described in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope image of the nickel-manganese bimetallic hydroxide NiMn-LDH synthesized in Example 1 of this invention;

[0027] Figure 3 The image shows the XRD pattern of the nickel-manganese bimetallic hydroxide NiMn-LDH@C described in Example 1 of this invention.

[0028] Figure 4 This is a transmission electron microscope (TEM) image of the NiMn-LDH@C nickel-manganese bimetallic hydroxide / activated carbon composite material described in Example 1 of this invention.

[0029] Figure 5This is a graph showing the electrocatalytic degradation of dichloroacetamide by the nickel-manganese bimetallic hydroxide NiMn-LDH@C described in Example 1 of this invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0031] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0032] In the quantitative experiments in the following examples, three replicate experiments were set up, and the average value of the results was taken.

[0033] Unless otherwise specified, the experimental methods in the following examples are conventional methods;

[0034] Example 1

[0035] This embodiment provides a method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system. The operation steps are as follows:

[0036] S1. Dissolve 0.02 mol / L nickel nitrate hexahydrate and 0.01 mol / L manganese nitrate tetrahydrate completely in deionized water. Then, add 0.017 mol / L activated carbon to the mixed solution and stir for 1 hour until homogeneous. The Ni content in the mixed solution... 2+ The molar concentration of Mn is 0.01 mol / L. 2+ The molar concentration is 0.005 mol / L;

[0037] S2. 1 mol / L ammonia solution was added dropwise to a mixed solution containing activated carbon. After the reaction was complete, the deposited solid was ground to obtain the nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn. LDH@C, its scanning electron microscope image is as follows Figure 1 As shown, the transmission electron microscope image is as follows: Figure 4 As shown.

[0038] S3. The current density in the three-dimensional electrode system is adjusted to 6.75 mA / cm². 2 The electrolyte is anhydrous sodium sulfate with a concentration of 25 g / L. 4.4 g of nickel-manganese bimetallic hydroxide / activated carbon electrode material is added between the graphite carbon working electrode plates in the three-dimensional aerated continuous flow electrolytic cell. The aeration rate is controlled at 1 L / min. The electrocatalytic degradation of water with a dichloroacetamide concentration of 10.5 mg / L is achieved.

[0039] Removal effect as Figure 5As shown, the removal rate of dichloroacetamide reached 65.21% at 60 minutes as time increased, and then the removal rate tended to stabilize. When the time increased from 60 min to 90 min, the removal rate only increased from 65.21% to 68.5%, which indicates that the removal capacity of dichloroacetamide basically reached its upper limit of about 68.5%.

[0040] Under the same conditions, this three-dimensional electrode system also exhibits excellent degradation performance for monochloroacetamide and trichloroacetamide, proving that the material prepared by this invention can be used as an electrode to achieve efficient degradation of halogenated disinfection byproducts.

[0041] The method for removing halogenated disinfection byproducts in water using a three-dimensional electrode system described in this invention can also be adjusted according to actual operational needs. 2+ The concentration of Mn is 0.008-0.012 mol / L. 2+ The concentration of activated carbon added is controlled at 0.015-0.018 mol / L, the electrolyte concentration is 24-26 g / L, and the current density is 6.35-7.15 mA / cm². 2 The aeration rate is 0.5-1.5 L / min.

[0042] Performance testing

[0043] 1. NiMn LDH Surface Morphology Testing

[0044] The nickel-manganese bimetallic hydroxide NiMn described in Example 1 of this invention was obtained by scanning electron microscopy. LDH surface morphology, scanning electron microscope image as follows: Figure 2 As shown.

[0045] from Figure 2 The material can be seen to be a layered crystal with a polygonal structure, exhibiting a good crystal structure. The high crystallinity indicates that the prepared LDH has good catalytic properties.

[0046] 2. NiMn LDH Synthesis Test

[0047] The nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn synthesized by the method in Example 1 above. The LDH@C sample was sent to a scientific compass for XRD characterization, and the results were plotted using Origin. The XRD characterization conditions were: scan speed 10° / min; scan angle range 10-90°.

[0048] Figure 3 NiMn bimetallic hydroxide / activated carbon composite material The XRD pattern of the LDH@C three-dimensional particle electrode material shows the presence of characteristic peaks 003, 006, 012, 015, 018, 110, and 113, which are consistent with the characteristic peaks of the standard card JCPDS#38-0715 (NiMn-LDH), further proving that the present invention has successfully synthesized NiMn-LDH.

[0049] 2. Free radical quenching experiment

[0050] The nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn synthesized according to the method in Example 1 above. LDH@C was used as a particle electrode for the electrocatalytic degradation of dichloroacetamide. A three-dimensional electrode system was assembled using graphite carbon plates as the working positive and negative electrodes. Tert-butanol was used as a quencher for hydroxyl radicals, and benzoquinone was used as a quencher for superoxide radicals. Free radical quenching experiments were conducted at a current density of 6.75 mA / cm². 2 When the electrolyte concentration is 25 g / L, the dichloroacetamide concentration is 10.5 mg / L, and the quencher concentration is 20 mg / L, 4.4 g of nickel-manganese bimetallic hydroxide / activated carbon electrode material is added to a three-dimensional aerated continuous flow electrolytic cell.

[0051] The degradation rate was tested after 120 minutes of energization, and the results showed a significant decrease in removal rate compared to the sample without quenching agent. This demonstrates that the NiMn nickel-manganese bimetallic hydroxide / activated carbon composite material prepared in this invention... LDH@C, as a particle electrode, relies primarily on the action of hydroxyl radicals and superoxide radicals for the efficient degradation of halogenated disinfection byproducts.

[0052] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system, characterized in that, The method includes the following steps: NiMn-LDH@C, a nickel-manganese bimetallic hydroxide / activated carbon composite material, is placed in a three-dimensional electrochemical reactor as a particle electrode to form a three-dimensional electrode system. Under the condition of electric aeration, the three-dimensional electrode system is used to perform electrochemical catalytic oxidation on water containing halogenated disinfection byproducts. The nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn-LDH@C is synthesized by the following steps: S1. Take nickel nitrate hexahydrate and manganese nitrate tetrahydrate and dissolve them completely in deionized water, then take activated carbon and put it into the mixed solution and stir evenly for 1 hour. S2. Ammonia water is added dropwise to a mixed solution containing activated carbon and the reaction is complete. The deposited solid is then ground to obtain the nickel-manganese bimetallic hydroxide / activated carbon composite material NiMn-LDH@C. The molar ratio of nickel nitrate hexahydrate to manganese nitrate tetrahydrate in S1 is 2:1; Ni in S1 mixed solution 2+ The molar concentration of Mn is 0.008-0.012 mol / L. 2+ The molar concentration is 0.004-0.006 mol / L; The concentration of activated carbon added in S1 is 0.015-0.018 mol / L.

2. The method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system as described in claim 1, characterized in that, The molar concentration of ammonia water is 0.8-1.2 mol / L.

3. The method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system as described in claim 1, characterized in that, The electrolyte in the three-dimensional electrode system is anhydrous sodium sulfate, and the working electrode material in the three-dimensional electrode system is a graphite carbon plate.

4. The method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system as described in claim 3, characterized in that, The electrolyte concentration is 24-26 g / L.

5. A method for removing halogenated disinfection byproducts from water using a three-dimensional electrode system as described in claim 1, characterized in that, The aeration rate is 0.5-1.5 L / min.

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