Electrochemical anode-cathode combined system and application thereof, and wastewater treatment method

Abstract

The application belongs to the technical field of wastewater treatment, and provides an electrochemical anode-cathode combined system, wherein a diaphragm divides an electrolytic cell into an anode chamber and a cathode chamber, the anode chamber is provided with a counter electrode and filled with activated carbon, the cathode chamber is provided with a working electrode and a reference electrode, the working electrode comprises a conductive base and a modified electroactive biofilm arranged on the surface of the conductive base, and the modified electroactive biofilm comprises an electroactive biofilm and palladium nanoparticles loaded on the electroactive biofilm.In the application, H* generated on the surface of the palladium nanoparticles on the electroactive biofilm can attack the carbon-halogen bond in PFASs, meanwhile, the electroactive biofilm can reduce nitrate by using electrode electrons, and then the activated carbon particles passing through the anode can be adsorbed and further purified and filtered, so that the electrochemical anode-cathode combined system provided by the application can effectively remove perfluoro / polyfluoroalkyl compounds and nitrate in wastewater at the same time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to an electrochemical anode-cathode combined system and application thereof and a wastewater treatment method. BACKGROUND

[0002] Perfluoro / polyfluoroalkyl substances (PFASs) are a class of artificially synthesized chemicals in which the C-H bond is partially or completely replaced by C-F bond. Due to the unique physicochemical properties, PFASs have been widely used in metal plating, textiles and foam fire extinguishing agents and other fields. However, PFASs have strong environmental persistence, bioaccumulation and are accompanied by high developmental and immunotoxicity, and are widely detected in wild animals and plants, sediments and water and other environmental media, which poses a great threat to human health and ecosystems.

[0003] At present, the removal methods of PFASs mainly include physical, chemical and biological methods. Traditional physical and chemical remediation methods require high investment, energy consumption and are prone to secondary pollution; although microbial degradation technology has been studied in recent years, its treatment rate is slow and it is difficult to achieve industrial application. Compared with the above, the hydrogenolysis reaction catalyzed by noble metal provides a new choice, and has controllable selectivity and activity for pollutant degradation under mild operating conditions.

[0004] Among them, metal nano-Pd has strong H* activation capacity and exhibits more superior catalytic dehalogenation capacity than other metals. However, the uniform and stable synthesis of nano-Pd catalyst and the effective and continuous generation of H* still pose certain challenges to the application of the technology. In addition, when PFASs and nitrate are simultaneously contained in wastewater, it is necessary to avoid the mutual influence of the two and to construct a synergistic system to effectively remove the two. SUMMARY

[0005] The purpose of the present application is to provide an electrochemical anode-cathode combined system and application thereof and a wastewater treatment method. The electrochemical anode-cathode combined system provided by the present application can effectively remove perfluoro / polyfluoroalkyl compounds and nitrate in wastewater at the same time.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] The present application provides an electrochemical anode-cathode combined system, which comprises an electrolytic cell and a diaphragm arranged in the electrolytic cell. The diaphragm divides the electrolytic cell into an anode chamber and a cathode chamber. The anode chamber is provided with a counter electrode and is filled with activated carbon. The cathode chamber is provided with a working electrode and a reference electrode.

[0008] The working electrode comprises a conductive substrate and a modified electroactive biofilm loaded on the surface of the conductive substrate; the modified electroactive biofilm comprises an electroactive biofilm and palladium nanoparticles loaded on the electroactive biofilm.

[0009] Preferably, the thickness of the electroactive biofilm is 46-66 mu m.

[0010] Preferably, the loading mass percentage of the palladium nanoparticles on the modified electroactive biofilm is 5%-8%.

[0011] Preferably, the particle size of the palladium nanoparticles is 5-30 nm.

[0012] Preferably, the counter electrode is a platinum electrode; and the reference electrode is an Ag / AgCl electrode.

[0013] Preferably, the particle size of the activated carbon is 0.7-1.2 mm.

[0014] The application also provides an application of the electrochemical anode-cathode combined system in treating wastewater containing perfluoro / polyfluoroalkyl compounds and nitrate.

[0015] The application also provides a wastewater treatment method using the electrochemical anode-cathode combined system, comprising the following steps:

[0016] The wastewater is injected from the top end of the cathode chamber, a reduction reaction occurs in the cathode chamber, pretreated water obtained from the bottom end of the cathode chamber flows into the anode chamber, filtration and adsorption are performed in the anode chamber, and treated water obtained from the top end of the anode chamber flows out.

[0017] The wastewater is wastewater containing perfluoro / polyfluoroalkyl compounds and nitrate.

[0018] Preferably, the working voltage of the reduction reaction is-1.2 V (vs. Ag / AgCl); and the temperature is 20±1 DEG C.

[0019] Preferably, the temperature of the filtration and adsorption is 20±1 DEG C.

[0020] The application provides an electrochemical anode-cathode combined system, which comprises an electrolytic cell and a diaphragm arranged in the electrolytic cell, the diaphragm divides the electrolytic cell into an anode chamber and a cathode chamber, the anode chamber is provided with a counter electrode and is filled with activated carbon; the cathode chamber is provided with a working electrode and a reference electrode; the working electrode comprises a conductive substrate and a modified electroactive biofilm loaded on the surface of the conductive substrate; the modified electroactive biofilm comprises an electroactive biofilm and palladium nanoparticles loaded on the electroactive biofilm. In the application, the H* generated on the surface of the palladium nanoparticles on the electroactive biofilm can attack the carbon-halogen bond in PFASs; meanwhile, the electroactive biofilm can reduce nitrate by using electrode electrons; in addition, the activated carbon particles in the anode chamber can further purify and filter after adsorption. The electrochemical anode-cathode combined system can effectively remove perfluoro / polyfluoroalkyl compounds and nitrate in wastewater at the same time by coupling a cathode reduction system and an anode adsorption and filtration system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 SEM image of the conductive substrate loaded with the electroactive biofilm obtained in Example 1;

[0022] Figure 2 SEM image of the working electrode obtained in Example 1;

[0023] Figure 3 EDS image of the working electrode obtained in Example 1;

[0024] Figure 4 EDS image of the electrode loaded with palladium nanoparticles obtained by a traditional electrochemical synthesis method;

[0025] Figure 5 Degradation curve of the removal of 6:2 Cl-PFAES in Example 3;

[0026] Figure 6 Degradation curve of the removal of NO3 - in Example 3.

[0027] Figure 7 Test curve of the content of 6:2 H-PFAES before and after entering and leaving the anode in Example 3;

[0028] Figure 8 Structural schematic diagram of the electrochemical anode-cathode combined system provided by the application. DETAILED DESCRIPTION

[0029] The application provides an electrochemical anode-cathode combined system, which comprises an electrolytic cell and a diaphragm arranged in the electrolytic cell, the diaphragm divides the electrolytic cell into an anode chamber and a cathode chamber, the anode chamber is provided with a counter electrode and is filled with activated carbon, the cathode chamber is provided with a working electrode and a reference electrode;

[0030] The working electrode comprises a conductive substrate and a modified electroactive biofilm loaded on the surface of the conductive substrate; the modified electroactive biofilm comprises an electroactive biofilm and palladium nanoparticles loaded on the electroactive biofilm.

[0031] In the present application, the thickness of the electroactive biofilm is preferably 46-66 μm, further preferably 50-65 μm, and more preferably 58-62 μm. The present application does not have special limitations on the type of active bacteria in the electroactive biofilm, and the skilled person in the art can be used. In the specific embodiments of the present application, the active bacteria are preferably Geobacter.

[0032] In the present application, the particle size of the palladium nanoparticles is preferably 5-30 nm, further preferably 10-25 nm, and more preferably 15-18 nm. In the present application, the mass percentage loading of palladium nanoparticles on the modified electroactive biofilm is preferably 5%-8%, and further preferably 6%-7%.

[0033] In the present application, the conductive substrate is preferably carbon felt. In the present application, the specific surface area of the carbon felt is large, and the use of carbon felt as a conductive substrate is conducive to the attachment of electroactive microorganisms.

[0034] In the present application, the working electrode is preferably prepared; the preparation method preferably comprises the following steps:

[0035] A biological electrochemical system is constructed with the conductive substrate as the anode and the stainless steel mesh as the cathode, and a solution containing active bacteria and a culture solution are mixed to obtain an inoculum;

[0036] A voltage of 1.0 V is applied between the anode and the cathode to acclimate, and a conductive substrate loaded with an electroactive biofilm is obtained;

[0037] The conductive substrate loaded with the electroactive biofilm is immersed in a culture solution containing sodium acetate and sodium chloropalladate to reduce and synthesize nanoparticles by microorganisms, and the working electrode is obtained.

[0038] In the present application, the size of the conductive substrate and the stainless steel mesh is preferably 10 cm x 4 cm.

[0039] The present application does not have special limitations on the concentration of active bacteria in the solution containing active bacteria, and the skilled person in the art can be used. In the present application, the solution containing active bacteria is preferably the anode effluent of a microbial fuel cell that has been running stably for more than 5 years.

[0040] In the present application, the culture solution preferably comprises 50 mmol / L of phosphate buffer, 12.5 mL / L of mineral solution, 5 mL / L of vitamin solution and 1 g / L of sodium acetate.

[0041] In the present application, the components and formula of the phosphate buffer are shown in Table 1.

[0042] Table 1 Components and formula of phosphate buffer

[0043] Ingredient Concentration (g / L) Ingredient Concentration (g / L) Na2HPO4 4.576 NH4CI 0.31 NaH2PO4 2.132 KCI 0.13

[0044] The components and formula of the mineral solution are shown in Table 2.

[0045] Table 2 Components and formula of mineral solution

[0046] Ingredient Concentration (g / L) Ingredient Concentration (g / L) MgSO4 3.0 [N(CH2COOH)3] 2.0 MnSO4 0.5 H3BO3 0.01 Na2MoO4 0.025 NaCI 1.0 <![CDATA[FeSO4·7H2O]]> 0.1 ZnCl2 0.13 [CuSO4·5H2O] 0.01 CaCl2·2H2O 0.1 Na2WO4.2H2O 0.025 CoCl2-6H2O 0.1 AlK(SO4)2.12H2O 0.01 [NiCl2·6H2O] 0.024

[0047] The components and formula of the vitamin solution are shown in Table 3.

[0048] Table 3 Components and formula of vitamin solution

[0049]

[0050]

[0051] In the present application, the volume ratio of the solution containing active bacteria and the culture solution is preferably 1:3.

[0052] In the present application, the domestication is preferably carried out in a mixed atmosphere of nitrogen and carbon dioxide; the volume ratio of nitrogen and carbon dioxide is preferably 4:1.

[0053] In the present application, the process of domestication preferably comprises:

[0054] The culture solution is pre-inflated with mixed gas (N2:CO2 volume ratio of 4:1) for 30 min to remove oxygen, to ensure anaerobic environment; a voltage of 1.0 V is applied between the cathode and the anode to carry out the first cycle of domestication; when the recorded current is 0, the inoculum is replaced with the culture solution to carry out the second cycle of domestication; when the recorded current is 0, the inoculum is replaced with the culture solution to carry out the third cycle of domestication.

[0055] In the present application, the concentration of sodium chloropalladate in the culture solution containing sodium acetate and sodium chloropalladate is preferably 1 mmol / L, and the concentration of sodium acetate is preferably 1 g / L.

[0056] In the present application, the temperature of microbial reduction is preferably 30℃, and the time is preferably 12 h.

[0057] In the present application, the counter electrode is preferably a platinum electrode; the reference electrode is preferably an Ag / AgCl electrode. In the present application, the diaphragm is preferably a cation exchange membrane, and in particular embodiments, the cation exchange membrane is specifically CMI-7000S cation exchange membrane.

[0058] In the present application, the particle size of the activated carbon is preferably 0.7-1.2 mm, further preferably 0.8-1.1 mm, and more preferably 0.9-1.0 mm.

[0059] The present application provides an electrochemical cathode and anode combined system structure diagram as shown in Figure 8 .

[0060] The present application also provides the application of the electrochemical cathode and anode combined system in treating wastewater containing perfluoro / polyfluoroalkyl compounds and nitrate.

[0061] The present application also provides a wastewater treatment method using the electrochemical cathode and anode combined system described in the above technical solution, comprising the following steps:

[0062] The wastewater is injected from the top end of the cathode chamber, a reduction reaction occurs in the cathode chamber, and the pretreated water obtained flows out from the bottom end of the cathode chamber into the anode chamber, and the pretreated water is filtered and adsorbed in the anode chamber, and the treated water flows out from the top end of the anode chamber;

[0063] The wastewater includes perfluoro / polyfluoroalkyl compounds and nitrate.

[0064] In the present application, the perfluoro / polyfluoroalkyl compound is preferably chlorine-containing PFASs, and specifically 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFAES). The present application does not have special limitations on the type of nitrate, which can be used by those skilled in the art.

[0065] In the present application, the working voltage of the reduction reaction is preferably -1.2 V (vs. Ag / AgCl); the temperature is preferably 20±1℃.

[0066] In the present application, the pretreated water is preferably pumped into the anode chamber by a peristaltic pump; the pumping rate of the pretreated water is preferably 3 mL·min -1 .

[0067] In the present application, the temperature of the filtration and adsorption is preferably 20±1℃.

[0068] In order to further illustrate the present application, the electrochemical cathode and anode combined system and its application, and the wastewater treatment method provided by the present application are described in detail below in conjunction with the drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0069] Example 1

[0070] A bioelectrochemical system was constructed with a carbon felt with a size of 10 cm x 4 cm as an anode and a stainless steel mesh with a size of 10 cm x 4 cm as a cathode, 250 mL of anode effluent of a microbial fuel cell stably operated for more than 5 years (active bacteria therein were Geobacter) and 750 mL of a phosphate buffer solution were mixed, and then 12.5 mL / L of a mineral solution, 5 mL / L of a vitamin solution and 1 g / L of sodium acetate were added (specific components are shown in Tables 1 to 3), and the mixture was deoxygenated by exposure to a mixed gas (N2:CO2=4:1) for 30 min to ensure an anaerobic environment;

[0071] A voltage of 1.0 V was applied between the cathode and the anode to perform the first period of domestication; when the recorded current was 0, the inoculum was replaced with the culture solution to perform the second period of domestication; when the recorded current was 0, the inoculum was replaced with the culture solution to perform the third period of domestication, and thus a conductive substrate loaded with an electroactive biofilm was obtained, wherein the thickness of the electroactive biofilm was 60 μm;

[0072] The conductive substrate loaded with the electroactive biofilm was immersed in a solution of sodium chloropalladate with a concentration of 1 mmol / L and sodium acetate with a concentration of 1 g / L, and was left in a 30°C incubator for 12 h, and thus the working electrode was obtained, wherein the particle size of the palladium nanoparticles was 15 to 18 nm, and the loading mass percentage was 6.8%.

[0073] Figure 1 is a SEM image of the conductive substrate loaded with the electroactive biofilm, Figure 2 is a SEM image of the working electrode, and Figures 1-2 It can be seen that the biofilm is uniformly and densely attached to the surface of the carbon felt, and the reduced and synthesized palladium nanoparticles are uniformly distributed on the surface of the bacteria;

[0074] Figure 3 is an EDS image of the working electrode, Figure 4 is an EDS image of the electrode loaded with palladium nanoparticles obtained by a traditional electrochemical synthesis method, and Figures 3-4 It can be seen that the microbial synthesis is not only a green synthesis method, but also the synthesized palladium nanoparticles are more uniformly distributed compared to the traditional electrochemical synthesis.

[0075] Example 2

[0076] An electrochemical cathode-anode combined system was constructed with the working electrode obtained in Example 1;

[0077] The electrolytic cell is divided into an anode chamber and a cathode chamber by a CMI-7000S cation exchange membrane, a platinum electrode is arranged in the anode chamber as a counter electrode, and active carbon with a particle size of 0.9-1.0 mm is filled in the anode chamber; a working electrode and an Ag / AgCl electrode are arranged in the cathode chamber to obtain an electrochemical anode-cathode combined system.

[0078] Example 3

[0079] The electrochemical anode-cathode combined system obtained in Example 2 is used to treat wastewater;

[0080] Wastewater containing 6:2Cl-PFAES and NO3 - (with the concentration of 6:2Cl-PFAES being 60 μM and the concentration of NO3 - is injected from the top end of the cathode chamber, a working voltage of-1.2 V (vs. Ag / AgCl) is applied, a reduction reaction occurs in the cathode chamber at 20±1℃, the obtained pretreated water flows out from the bottom end of the cathode chamber, and is pumped into the anode chamber at a pumping rate of 3 mL·min -1 at 20±1℃, filtration and adsorption are performed in the anode chamber, and the obtained treated water flows out from the top end of the anode chamber.

[0081] Test 1

[0082] After the combined system is operated for 5 h, the concentrations of 6:2Cl-PFAES and NO3 - in the samples taken at regular time intervals are detected, and a conductive substrate loaded with electroactive biofilm is used as a control;

[0083] Figure 5 is a degradation curve of 6:2Cl-PFAES, and Figure 6 is a degradation curve of NO3 - It can be seen from Figures 5-6 that, compared with the control group, the experimental group with the working electrode loaded with palladium nanoparticles has good removal effect on 6:2Cl-PFAES and NO3 - , and the palladium nanoparticles can promote the reduction of nitrate by microorganisms.

[0084] Test 2

[0085] The wastewater at the inlet end and the outlet end of the anode chamber is sampled respectively, and the concentrations of 6:2Cl-PFAES dechlorination and hydrogenation products (referred to as 6:2H-PFAES) are detected and compared, and an electrochemical system without filling active carbon particles in the anode chamber is used as a control;

[0086] The obtained test curve is shown in Figure 7 , wherein the influent represents pretreated water (i.e. the inlet end), and the effluent represents the effluent after anode treatment (i.e. the outlet end), fromFigure 7 It can be seen that the active carbon particles filled in the anode chamber have good filtering and adsorbing performance on the product after the dechlorination and hydrogenation of PFASs, and can be used for the secondary complete treatment of the dehalogenation by-products.

[0087] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, and these embodiments all belong to the protection scope of the present application.

Claims

1. An electrochemical anode-cathode combined system, comprising an electrolytic cell and a diaphragm disposed in the electrolytic cell, the diaphragm dividing the electrolytic cell into an anode chamber and a cathode chamber, characterized in that, The anode chamber is provided with a counter electrode and filled with activated carbon, and the cathode chamber is provided with a working electrode and a reference electrode; The working electrode includes a conductive substrate and a modified electroactive biofilm loaded on the surface of the conductive substrate; The modified electroactive biomembrane comprises an electroactive biomembrane and palladium nanoparticles loaded on the electroactive biomembrane; Wastewater is injected from the top of the cathode chamber, treated in the cathode chamber, and then flows out from the bottom of the cathode chamber into the anode chamber. After being treated in the anode chamber, it flows out from the top of the anode chamber.

2. The electrochemical anode-cathode combined system according to claim 1, characterized in that, The thickness of the electroactive biomembrane is 46~66μm.

3. The electrochemical anode-cathode combined system according to claim 1 or 2, characterized in that, The palladium nanoparticles are loaded with a mass percentage of 5% to 8% on the modified electroactive biomembrane.

4. The electrochemical anode-cathode combined system according to claim 1, characterized in that, The palladium nanoparticles have a particle size of 5~30 nm.

5. The electrochemical anode-cathode combined system according to claim 1, characterized in that, The counter electrode is a platinum electrode; the reference electrode is an Ag / AgCl electrode.

6. The electrochemical anode-cathode combined system according to claim 1, characterized in that, The activated carbon has a particle size of 0.7~1.2 mm.

7. The application of the electrochemical anode-cathode combined system according to any one of claims 1 to 6 in the treatment of wastewater containing perfluorinated / polyfluorinated alkyl compounds and nitrates.

8. A wastewater treatment method, characterized in that, The electrochemical anode-cathode combined system according to any one of claims 1 to 6 includes the following steps: Wastewater is injected from the top of the cathode chamber, where a reduction reaction occurs. The resulting pretreated water flows out from the bottom of the cathode chamber and into the anode chamber, where it undergoes filtration and adsorption. The resulting treated water flows out from the top of the anode chamber. The wastewater contains perfluorinated / polyfluorinated alkyl compounds and nitrates.

9. The wastewater treatment method according to claim 8, characterized in that, The operating voltage for the reduction reaction is -1.2V (vs. Ag / AgCl); the temperature is 20±1℃.

10. The wastewater treatment method according to claim 8, characterized in that, The temperature for filtration and adsorption is 20±1℃.

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