Iron-based cathode material for wastewater treatment as well as preparation method and application of iron-based cathode material

Abstract

The invention discloses an iron-based cathode material for wastewater treatment as well as a preparation method and application of the iron-based cathode material. Aiming at the problem that activation of persulfate at a cathode is inhibited due to electrostatic repulsion between the cathode surface and persulfate in a cathode activated persulfate reaction system, a strategy of regulating and controlling the cathode surface / persulfate by a cation layer is provided, a metal cation layer is deposited on the cathode surface, an interface with positive Zeta potential appears, and activation of the persulfate at the cathode is inhibited. The interface electrostatic repulsion is effectively weakened, the interface aggregation effect of persulfate on the cathode is remarkably enhanced, and the activation of persulfate is improved. The iron-based cathode material disclosed by the invention can be used for degrading organic matters in water by electrochemically activating persulfate, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and particularly relates to an iron-based cathode material for wastewater treatment and a preparation method and application thereof. BACKGROUND

[0002] With the acceleration of industrialization and rapid population growth, wastewater containing toxic and harmful organic matter has become a major challenge to environmental protection, restricting the sustainable development of human society, and has become a research hotspot of current countries. The above-mentioned organic matter such as drugs, dyes, pesticides and microplastics, not only widely exists in surface water and groundwater, but also has strong biological toxicity, environmental persistence and biological accumulation, which poses a potential threat to the ecological environment and human health, so wastewater resource utilization plays an important role in improving water resource shortage.

[0003] In the prior art, flocculation sedimentation method, membrane filtration method and the like are common methods for removing organic matter in water, but these methods only realize the separation of organic matter, and further degradation of organic matter existing in the solid phase is still needed. Biological degradation method and advanced oxidation method are often used for degradation of organic matter, but the biological degradation method has the disadvantages of long treatment time and low degradation efficiency, and the degradation effect of the advanced oxidation method is relatively good, and among them, the electrochemical activation persulfate method has good practicability.

[0004] HSO5 - / S2O8 2- ions are reduced to generate active oxygen species (ROS) such as sulfate radicals (SO4· - ) and hydroxyl radicals (·OH) at the cathode, and then ROS reacts with organic matter to oxidize it into smaller molecules or completely mineralize it into CO2 and H2O. There is a difficulty problem of slow interfacial mass transfer in the process of degrading organic pollutants by electrochemical activation persulfate (PS) method. In the cathode region, the cathode surface has a negative charge, and PS exists in the form of negative ions HSO5 - / S2O8 2- Under the interaction of the same charge, electrostatic repulsion occurs between them, and the ions are difficult to effectively adsorb to the cathode surface, thereby affecting the activation of PS and further affecting the degradation rate of organic matter. Therefore, there is an urgent need for an electrode material that can strengthen the aggregation effect of PS at the cathode interface. SUMMARY

[0005] To solve at least part of the technical problems in the prior art, the present application provides an iron-based cathode material for wastewater treatment and a preparation method and application thereof. Specifically, the present application includes the following contents.

[0006] A first aspect of the present invention provides a method for preparing an iron-based cathode material for wastewater treatment, comprising the following steps: (1) using a strong oxidizing solution to functionalize the surface of the carbon cloth to obtain a pretreated carbon cloth; (2) using a first deposition solution to electro-deposit iron oxide on the pretreated carbon cloth to obtain a FeOOH electrode; (3) using a second deposition solution to electro-deposit metal cations on the FeOOH electrode to obtain an M-FeOOH electrode, wherein M is a metal cation, and the first deposition solution and the second deposition solution are different.

[0007] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, in step (1), the strong oxidizing solution includes at least one of concentrated nitric acid, concentrated sulfuric acid, sodium hypochlorite solution and potassium permanganate solution.

[0008] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, in step (2), the first deposition liquid comprises at least one of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate and ferrous nitrate.

[0009] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, in step (3), the metal cations include high-valence metal cations.

[0010] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, the metal cations include Zr 4+ 、Nd 3+ 、La 3+ 、Ce 3+ Mg 2+ 、Cu 2+ 、Zn 2+ 、Mn 2+ 、Na + and K + At least one of .

[0011] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, in step (3), the second deposition solution includes a compound containing the metal cation.

[0012] In certain embodiments, according to the method for preparing an iron-based cathode material for wastewater treatment of the present invention, the current density of the electrodeposition is 5-15 mA / cm 2 The electrodeposition time is 10-30 min.

[0013] The second aspect of the present invention provides an iron-based cathode material obtained by the preparation method described in the first aspect of the present invention.

[0014] The third aspect of the present invention provides the use of the iron-based cathode material according to the second aspect of the present invention in electrochemically activating persulfate to degrade organic matter in water.

[0015] In certain embodiments, according to the use of the present invention, the organic matter comprises at least one of phenol, p-chlorophenol, sulfadiazine, sulfamethoxazole and sulfamethoxazole.

[0016] The present invention addresses the problem of electrostatic repulsion between the cathode surface and PS in a cathode-activated persulfate reaction system, which inhibits PS activation at the cathode. A strategy for regulating the cathode surface / PS solution using a cationic layer is proposed. By depositing a metal cation layer on the cathode surface, an interface with a positive zeta potential is formed, effectively weakening the interfacial electrostatic repulsion and significantly enhancing the PS interfacial aggregation effect at the cathode, promoting persulfate activation to produce reactive oxygen species, and thereby promoting the effective degradation of organic matter in water. Furthermore, the iron-based cathode material of the present invention has the advantages of a simple preparation process, high activity, large specific surface area, and low toxicity, has broad application prospects, and can promote research and experimental development in environmental protection technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The stability of the iron-based cathode material of the present invention to the degradation of phenol is shown.

[0018] Figure 2 The zero charge potential of multiple degradation experiments of the iron-based cathode material of the present invention is shown.

[0019] Figure 3 The zero charge potentials of different metal cation layer electrode materials are shown.

[0020] Figure 4 The stability of the electrode material prepared by the self-assembly method towards the degradation of phenol is shown.

[0021] Figure 5 The zero charge potential of electrode materials obtained by different methods is shown.

[0022] Figure 6 The degradation performance of electrode materials obtained by different deposition methods on various pollutants is shown. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values, the endpoints are included within the range. Unless otherwise stated, the use of "or" includes "and" or "and / or" unless otherwise stated. Unless otherwise stated, the use of "a" or "an" includes "one or more" or "at least one", but not one and only one, and the use of "an" or "a" shall not limit the meaning of "one", unless otherwise stated. In addition, grammatical articles, such as "a", "an" and "the" are intended to imclude both "a" and "an", as well as "an" and "the", respectively, unless otherwise stated.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application. All patents and publications mentioned herein are incorporated by reference whether or not specifically

[0026] [Preparation method] In one aspect of the present application, a preparation method of an iron-based cathode material is provided, which comprises steps (1)-(3) and will be described in detail as follows.

[0027] In step (1) of the present application, a pre-treated carbon cloth is obtained by surface functionalization of carbon cloth using a strong oxidizing solution. The source of the carbon cloth is not particularly limited and a commercially available product can be used; the strong oxidizing solution is not particularly limited and examples thereof include, but are not limited to, concentrated nitric acid, concentrated sulfuric acid, sodium hypochlorite solution, potassium permanganate solution, and the like. In a preferred embodiment, the strong oxidizing solution is 65% concentrated nitric acid. It can be understood that the carbon cloth can be washed or dried before or after surface functionalization of the carbon cloth, and the washing liquid is not particularly limited and examples thereof include, but are not limited to, acetone, ethanol, deionized water, and the like.

[0028] In step (2) of the present application, a FeOOH electrode is obtained by electrodeposition of iron oxide on the pre-treated carbon cloth using a first deposition solution, wherein the first deposition solution comprises an iron-containing compound, and the iron-containing compound is not particularly limited and examples thereof include, but are not limited to, ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate, ferrous nitrate, and the like.

[0029] In step (3) of the present application, a M-FeOOH electrode is obtained by electrodeposition of metal cations on the FeOOH electrode using a second deposition solution, wherein M is a metal cation, and the metal cation comprises a high-valence metal cation, and the high-valence metal cation is not particularly limited and examples thereof include, but are not limited to, Zr 4+ , Nd 3+ , La3+ Ce 3+ etc.; the second deposition solution comprises a compound of the metal cation, examples of which include but are not limited to ZrOCl2, NdCl3, LaCl3, La(NO3)3, CeCl3, etc. In a preferred embodiment, the metal cation is Zr 4+ , and the second deposition solution is a solution comprising ZrOCl2.

[0030] To better strengthen the effect of peroxysulfate on the interface accumulation of the cathode material, the current density and time of the electro-deposition of the present application can be controlled within a suitable range. In the present application, the current density of the electro-deposition is 5-15 mA / cm 2 , preferably 6-14 mA / cm 2 , more preferably 7-13 mA / cm 2 , even more preferably 8-12 mA / cm 2 , for example 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12 mA / cm 2 , and the time of the electro-deposition is 5-30 min, preferably 5-25 min, more preferably 5-20 min, even more preferably 5-15 min, for example 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 min. In a preferred embodiment, the current density of the electro-deposition is 10 mA / cm 2 , and the time of the electro-deposition is 10 min.

[0031] In a preferred embodiment, the working electrode, the counter electrode and the reference electrode of the electro-deposition are the pretreated carbon cloth, the platinum sheet and the Ag / AgCl electrode, respectively.

[0032] [iron-based cathode material] In one aspect of the present application, an iron-based cathode material is provided, which is obtained by the preparation method described in the present application.

[0033] In a preferred embodiment, the iron-based cathode material of the present application has a surface charge of not less than +0.13 V, a degradation rate of not less than 94.93% for sulfamethizole (SMT), a degradation rate of not less than 95.67% for sulfamethoxazole (SMX), a degradation rate of not less than 99.01% for sulfadiazine (SDZ), a degradation rate of not less than 98.64% for 4-chlorophenol (4-CP), a degradation rate of 100% for phenol, and a degradation performance of more than 95% for phenol after three organic matter degradation.

[0034] [application] In one aspect of the present application, the application of the iron-based cathode material described in the present application in electrochemical activation of persulfate for degradation of organic matter in water is provided. The organic matter is not particularly limited, and examples thereof include, but are not limited to, phenol, p-chlorophenol, sulfadiazine, sulfamethoxazole, sulfisomidine, and the like.

[0035] In a preferred embodiment, the cathode of the organic matter degradation system is the iron-based cathode material described in the present application, the anode is a PbO2 electrode, the current density is 2-10 mA / cm 2 , and the persulfate concentration is 0-2.5 mmol / L.

[0036] Examples This example shows the process of preparing a Zr 4+ -FeOOH electrode by a two-step electrodeposition method.

[0037] 1. Preparation method (1) The carbon cloth was ultrasonically cleaned in acetone and anhydrous ethanol for 10-30 min, respectively, to remove surface impurities, and then washed with deionized water. The carbon cloth was placed in concentrated HNO3(65%) for refluxing at 100°C for 5 h for surface functionalization treatment, and finally, the carbon cloth was washed with deionized water and dried at 80-120°C to obtain a pretreated carbon cloth.

[0038] (2) A Zr 4+ -FeOOH was electrodeposited on the pretreated carbon cloth by a two-step electrodeposition method. Specifically, the carbon cloth, platinum sheet, and Ag / AgCl were used as the working electrode, counter electrode, and reference electrode, respectively, the electrolyte was Na2SO4, and the deposition solution was an aqueous solution of FeCl2·4H2O. The deposition was carried out at a current density of 10 mA / cm 2 for 10 min. The electrode was washed with deionized water and dried at 105°C to obtain a FeOOH electrode; the FeOOH electrode was placed in an aqueous solution of ZrOCl2·8H2O, and the deposition was carried out at a current density of 10 mA / cm 2 for 10 min. The electrode was washed with deionized water and dried at 105°C to obtain a Zr 4+ -FeOOH electrode.

[0039] 2. Electrode stability determination 2.1 Determination method The Zr 4+ -FeOOH electrode (two-step electrodeposition) was subjected to a stability test for degrading pollutants. The pollutant was phenol, the pollutant concentration was 20 mg / L, the PS concentration was 2 mmol / L, and the current density was 10 mA / cm 2After the reaction, the electrode was rinsed with deionized water and dried at 105°C. Multiple pollutant degradation experiments were performed, and the surface charge of the electrode after the reaction was completed was tested.

[0040] 2.2 Measurement results The results are as follows Figure 1 and Figure 2 As shown, Zr 4+ -FeOOH electrode (two-step electrodeposition) was used to conduct three organic matter degradation experiments. The degradation performance of phenol was above 95% and the surface charge of the electrode was above +0.10 V. It can be seen that Zr 4+ -FeOOH (two-step electrodeposition) has better stability.

[0041] Comparative Example 1 The following shows the preparation of X by electrodeposition and self-assembly + -FeOOH electrode process.

[0042] 1. Preparation (1) The carbon cloth was ultrasonically cleaned in acetone and anhydrous ethanol for 10-30 min each to remove surface impurities, and then thoroughly washed with deionized water. The carbon cloth was refluxed in concentrated HNO3 (65%) at 100°C for 5 h for surface functionalization treatment. Finally, the carbon cloth was rinsed with deionized water and dried at 80-120°C to obtain the pretreated carbon cloth.

[0043] (2) Electrodepositing FeOOH electrodes on the pretreated carbon cloth (the method is the same as in the embodiment), immersing the FeOOH electrodes in various metal cation solutions to adsorb metal cation layers using a self-assembly method, and preparing X + -FeOOH electrode (X + Zr 4+ 、Nd 3+ 、La 3+ 、Ce 3+ Mg 2+ 、Cu 2+ 、Zn 2+ 、Mn 2+ 、Na + and K + ).

[0044] 2. Performance Testing 2.1 Surface electrode potential Determine different X + -FeOOH electrode material surface electrode potential, the results are as follows Figure 3 As shown, the surface electrode potential from large to small is: Zr 4+ >Nd 3+ >La 3+>Ce 3+ >Mg 2+ >Cu 2+ >Zn 2+ >Mn 2+ >Na + >K + .

[0045] 2.2 Electrode stability Determination of Zr prepared in this comparative example 4+ -Stability of FeOOH electrode, the results are as follows Figure 4 As shown in the figure, the phenol degradation effect was only 50% after repeated use for the second time. The results showed that the Zr 4+ The stability of the FeOOH electrode needs to be further improved.

[0046] Comparative Example 2 The following shows the one-step electrodeposition method for preparing Zr 4+ -FeOOH electrode process.

[0047] 1. Preparation (1) The carbon cloth was ultrasonically cleaned in acetone and anhydrous ethanol for 10-30 min each to remove surface impurities, and then thoroughly washed with deionized water. The carbon cloth was refluxed in concentrated HNO3 (65%) at 100°C for 5 h for surface functionalization treatment. Finally, the carbon cloth was rinsed with deionized water and dried at 80-120°C to obtain the pretreated carbon cloth.

[0048] (2) One-step electrodeposition method was used to prepare Zr on pretreated carbon cloth 4+ -FeOOH electrode, specifically, carbon cloth, platinum sheet, and Ag / AgCl were used as working electrode, counter electrode, and reference electrode, respectively. The electrolyte was Na2SO4, and the deposition solution was a mixed solution of FeCl2·H2O and ZrOCl2·6H2O. The deposition current density was 10 mA / cm 2 The deposition time was 20 min, the electrode was washed with deionized water, dried at 105 °C and used for preparation of Zr 4+ -FeOOH electrode.

[0049] 2. Performance Testing 2.1 Surface charge measurement The surface charge of the electrodes of the embodiment and the comparative example was measured by zero charge potential method. Figure 5 As shown in the figure, the surface charge of the FeOOH electrode is -0.14 V, and the Zr 4+ -FeOOH electrode (one-step electrodeposition) has a surface charge of +0.07 V, Zr 4+-FeOOH electrode (two-step electrodeposition) has a surface charge of +0.13 V. It can be seen that the order of surface charge is: Zr 4+ -FeOOH electrode (two-step electrodeposition) > Zr 4+ -FeOOH electrode (one-step electrodeposition) > FeOOH electrode.

[0050] 2.2 Pollutant degradation performance test The pollutant degradation performance tests were performed on the electrodes of the embodiment and the comparative example, respectively. The pollutants were phenol, para-chlorophenol (4-CP), sulfadiazine (SDZ), sulfamethoxazole (SMX), and sulfamethoxazole (SMT). The pollutant concentration was 20 mg / L, the PS concentration was 2 mmol / L, and the current density was 10 mA / cm 2 The reaction time was 30 min. Figure 6 As shown, Zr 4+ -FeOOH electrode (two-step electrodeposition) has significantly better pollutant degradation performance than Zr 4+ -FeOOH electrode (one-step electrodeposition).

[0051] In summary, there is the same charge between the cathode and PS, so there is an electrostatic repulsion. The electrode prepared by the two-step electrodeposition method has a more positive surface charge than the electrode prepared by the one-step electrodeposition method. The electrode surface has a better electrostatic attraction to PS, which can better activate PS to produce ROS, thereby more effectively degrading pollutants. 4+ -FeOOH electrode (two-step electrodeposition) has better pollutant degradation performance.

[0052] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified or some of the technical features thereof may be replaced with equivalents. Such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an iron-based cathode material for wastewater treatment, characterized in that: The following steps are involved: (1) using a strong oxidizing solution to functionalize the surface of the carbon cloth to obtain a pretreated carbon cloth; (2) using a first deposition solution to electro-deposit iron oxide on the pretreated carbon cloth to obtain a FeOOH electrode; (3) Electrodepositing metal cations on the FeOOH electrode using a second deposition solution to obtain an M-FeOOH electrode, wherein M is a metal cation, and the first deposition solution and the second deposition solution are different.

2. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: In step (1), the strong oxidizing solution includes at least one of concentrated nitric acid, concentrated sulfuric acid, sodium hypochlorite solution and potassium permanganate solution.

3. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: In step (2), the first deposition liquid includes at least one of ferric chloride, ferrous chloride, ferric sulfate, ferrous sulfate, ferric nitrate and ferrous nitrate.

4. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: In step (3), the metal cations include high-valence metal cations.

5. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: The metal cations include Zr 4+ 、Nd 3+ 、La 3+ 、Ce 3+ Mg 2+ 、Cu 2+ 、Zn 2+ 、Mn 2+ 、Na + and K + At least one of .

6. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: In step (3), the second deposition liquid includes a compound containing the metal cation.

7. The method for preparing an iron-based cathode material for wastewater treatment according to claim 1, wherein: The current density of the electrodeposition is 5-15 mA / cm 2 The electrodeposition time is 10-30 min.

8. An iron-based cathode material, characterized in that The compound is obtained by the preparation method according to any one of claims 1 to 7.

9. The use of the iron-based cathode material in wastewater treatment according to claim 8, characterized in that: The iron-based cathode material is used for electrochemically catalyzing persulfate, thereby degrading organic matter in water.

10. The use according to claim 9, characterized in that The organic matter includes at least one of phenol, p-chlorophenol, sulfadiazine, sulfamethoxazole and sulfamethoxazole.

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