Modified manganese-based material for sewage treatment as well as preparation method and application of modified manganese-based material

Abstract

The invention discloses a modified manganese-based material for sewage treatment and a preparation method and application thereof, and belongs to the technical field of transition metal catalytic materials. The preparation method comprises the following steps: (1) washing and drying a three-dimensional substrate material in an acid solution and deionized water in sequence to prepare a pretreated substrate material; (2) mixing a manganese source, a transition metal precursor and a surfactant in an aqueous solution, carrying out hydrothermal reaction, and drying to obtain a modified manganese-based powder catalyst; and (3) preparing modified manganese-based powder catalyst slurry, dropwise adding the modified manganese-based powder catalyst slurry on the pretreated substrate material, and drying. The prepared modified manganese-based material has H2O2 selectivity, has a good degradation effect on organic wastewater such as dyes, chemical nickel plating and morpholine derivatives, is high in stability and simple in production process, and effectively solves the problems of low H2O2 selectivity, poor organic wastewater degradation effect, low stability and the like in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of transition metal catalytic materials, and specifically relates to a modified manganese-based material for sewage treatment and a preparation method and application thereof. Background Art

[0002] With the rapid development of the economy, people's requirements for the living environment are getting higher and higher. Environmental pollution issues have received widespread attention, and water pollution is one of them. Organic wastewater has become a major problem in solving water pollution due to its complex components and poor biodegradability. As a type of advanced oxidation, electro-Fenton technology has the advantages of high pollutant degradation rate, less secondary pollution, small footprint, and easy operation and control. Many researchers at home and abroad have used this technology to treat various organic wastewaters and achieved good results. At the same time, people have conducted in-depth research and found that how to improve the catalytic activity and H2O2 selectivity of cathode materials is the key issue to enhance the degradation efficiency of the electro-Fenton system, which is closely related to the operating economy of the electro-Fenton technology. The modification of cathode materials is one of the means to solve the above problems at home and abroad.

[0003] Electro-Fenton cathode materials usually include precious metals, transition metals, carbon materials, etc. Due to the scarcity and high price of precious metals, transition metal oxides and their alloys and carbon-based materials have been widely studied. Among them, transition metal manganese-based materials produce hydrogen peroxide (H2O2) through oxygen reduction reaction (ORR) and are a promising low-cost electrocatalyst material with strong metal adjustability, adaptability and excellent catalytic activity. However, the catalytic activity and H2O2 selectivity of pure metal Mn are still somewhat different from those of precious metals. How to improve the catalytic activity and selectivity of metal Mn and prepare Mn-based electrode materials with high catalytic activity and selectivity has great research value. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a modified manganese-based material for sewage treatment and its preparation method and application, so as to solve the problems of low H2O2 selectivity, poor organic wastewater degradation effect and low stability of existing manganese-based materials.

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

[0006] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0007] (1) washing the three-dimensional substrate material in an acidic solution and deionized water in sequence, and drying, to obtain a pretreated substrate material;

[0008] (2) mixing a manganese source, a transition metal precursor and a surfactant in an aqueous solution, performing a hydrothermal reaction, and drying to obtain a modified manganese-based powder catalyst;

[0009] (3) Prepare a modified manganese-based powder catalyst slurry, drop it on the pretreated base material, and dry it to obtain the catalyst.

[0010] The beneficial effects of the present invention are as follows: the present invention improves manganese oxide by adding a surfactant to combine with metal ions Mn, promotes the cyclic transformation of various valence states of Mn by adding low-valent metal oxides as transition metals, utilizes surfactants to increase the specific surface area of ​​the material and thus increase the active sites, thereby improving the catalytic degradation performance, and effectively improving the selectivity of manganese-based electrode materials for hydrogen peroxide and the electro-Fenton degradation effect.

[0011] Furthermore, in step (1), the three-dimensional substrate material is graphite felt, carbon felt, porous carbon or activated carbon fiber; and the acidic solution is nitric acid solution with a concentration of 1-3 mol / L.

[0012] Furthermore, in step (1), the washing time in the acidic solution is 12-16 hours, and the washing in deionized water is neutral; the drying temperature is 60-90° C., and the drying time is 4-8 hours.

[0013] Furthermore, in step (2), the manganese source is one of manganese sulfate, potassium permanganate, manganese chloride and manganese nitrate; the transition metal precursor is at least one of iron, cobalt and nickel metal salts; and the surfactant is at least one of stearic acid, oleic acid, lauric acid, sodium dodecyl sulfate, hexadecyltrimethylammonium chloride, sodium dodecyl sulfonate, long-chain alkyl amino acid and Tween 80.

[0014] The beneficial effect of adopting the above further technical solution is: the present invention effectively improves the activity of the prepared electrode material by adding a surfactant, increases the specific surface area of ​​the material and increases the active sites by changing the physicochemical properties of the metal surface, thereby promoting the electro-Fenton degradation effect.

[0015] Furthermore, the transition metal precursor is at least one of ferric chloride, ferric sulfate, ferric nitrate, ferric acetate, cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, nickel chloride, nickel nitrate, nickel sulfate or nickel acetate.

[0016] Furthermore, in step (2), the concentration of surfactant in the aqueous solution after mixing is 2-10 g / L; the molar ratio of manganese to transition metal is 1:1-8:1, and the concentration of manganese in the aqueous solution is 0.1-0.5 mol / L.

[0017] Furthermore, in step (2), the temperature of the hydrothermal reaction is 80-180° C., and the time is 2-12 h.

[0018] Furthermore, the manganese-based powder catalyst slurry in step (3) is prepared by the following method: a modified manganese-based powder catalyst, polytetrafluoroethylene emulsion, water and ethanol are mixed and ultrasonically prepared.

[0019] Furthermore, the concentration of the modified manganese-based powder catalyst in the slurry is 0.08-0.12 mg / mL, and the volume ratio of the polytetrafluoroethylene emulsion, water and ethanol is 3-7:20-30:450-500.

[0020] A modified manganese-based material for sewage treatment is prepared by the above preparation method.

[0021] The modified manganese-based material for sewage treatment is used in the degradation of dyes, chemical nickel plating and morpholine derivative organic wastewater.

[0022] The present invention has the following beneficial effects:

[0023] (1) The modified manganese-based material prepared by the present invention has high H2O2 selectivity, good degradation effect on organic wastewater, high stability, and simple production process, which effectively solves the problems of low H2O2 selectivity, poor organic wastewater degradation effect and low stability in the prior art.

[0024] (2) In the modified manganese-based material obtained by the present invention, metal Mn and Fe are evenly distributed on the surface of the material, and the surfactant and Fe 3+ The addition of MnFeO increases the specific surface area and H2O2 selectivity of manganese oxide, improves the hydrophilicity, and thus enhances the electro-Fenton degradation performance of the electrode material. x -SDS can achieve a degradation rate of over 90% for dyes and morpholine derivatives, and a maximum removal rate of 99.2% for EDTA in EDTA-Ni wastewater, 89% for COD removal, and 89% for Ni 2+ The removal rate of the catalyst is 85%. 2+ The adsorption capacity reaches 287 mg / g, the H2O2 selectivity can reach more than 90%, and it has good stability and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The degradation effect test results in Experimental Example 1;

[0026] Figure 2 The degradation effect test results in Experimental Example 2;

[0027] Figure 3 The degradation effect test results in Experimental Example 3;

[0028] Figure 4 The degradation effect test results in Experimental Example 4;

[0029] Figure 5 The degradation effect test results in Experimental Example 5;

[0030] Figure 6The degradation effect test results in Experimental Example 6;

[0031] Figure 7 are SEM images of the modified manganese-based materials in Experimental Example 6, wherein (a)-(c) are SEM images of the modified manganese-based materials obtained in Comparative Example 3, Comparative Example 2 and Example 11, respectively, and (d)-(g) are EDS images of the modified manganese-based material obtained in Example 11;

[0032] Figure 8 is the XRD image of the modified manganese-based material in Experimental Example 6;

[0033] Fig. 9 The contact angle test images of the modified manganese-based material in Experimental Example 6, wherein (a)-(c) are contact angle test images of the modified manganese-based material obtained in Comparative Example 3, Comparative Example 2 and Example 11, respectively;

[0034] Fig.10 This is a graph showing the test results of H2O2 selectivity and electron transfer number of the modified manganese-based material in Experimental Example 6;

[0035] Fig.11 The degradation effect of the modified manganese-based material on different organic wastewaters in Experimental Example 6;

[0036] Fig.12 The stability test results of the modified manganese-based material in Experimental Example 6;

[0037] Fig.13 The quenching test results of the modified manganese-based material in Experimental Example 6;

[0038] Fig.14 The test results of ·OH radicals generated during the electro-Fenton degradation of Rh B by the modified manganese-based material in Experimental Example 6;

[0039] Fig.15 This is the degradation effect of the modified manganese-based material in Experimental Example 7 on NMMO wastewater of different concentrations. DETAILED DESCRIPTION

[0040] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0041] Embodiment 1:

[0042] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0043] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0044] (2) 80 mL of the impregnation solution containing the manganese source, transition metal precursor and surfactant was placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal autoclave and hydrothermalized at 140°C for 2 hours. After cooling, it was washed and dried to obtain a modified manganese-based powder catalyst. The impregnation solution was prepared by the following method: a surfactant was added to 80 mL of deionized water at a concentration of 2 g / L, and then a manganese source and a transition metal precursor were added and ultrasonically mixed to obtain a modified manganese-based powder catalyst. The surfactant was hexadecyltrimethylammonium bromide; the manganese source was manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5), and the manganese source concentration was 0.4 mol / L; the transition metal precursor was ferric nitrate, and the molar ratio of manganese to iron in the impregnation solution was 2:1.

[0045] (3) Add 5 mg of the modified manganese-based powder catalyst obtained in step (2), 0.005 mL of polytetrafluoroethylene emulsion, 0.025 mL of water and 0.47 mL of ethanol into a sample tube, and obtain a slurry by ultrasonication. Then, drop the slurry on the pretreated substrate material obtained in step (1), and dry it to obtain a modified manganese-based material.

[0046] Embodiment 2:

[0047] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0048] The preparation method is the same as that of Example 1, except that the transition metal precursor in step (2) is changed to cobalt nitrate to obtain a modified manganese-based material.

[0049] Embodiment 3:

[0050] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0051] The preparation method is the same as that of Example 1, except that the transition metal precursor in step (2) is changed to nickel nitrate to obtain a modified manganese-based material.

[0052] Embodiment 4:

[0053] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0054] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0055] (2) 80 mL of the impregnation solution containing the manganese source, transition metal precursor and surfactant was placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal autoclave for hydrothermal heating at 100°C for 2 hours. After cooling, it was washed and dried to obtain a modified manganese-based powder catalyst. The impregnation solution was prepared by the following method: a surfactant was added to 80 mL of deionized water at a concentration of 2 g / L, and then a manganese source and a transition metal precursor were added and ultrasonically mixed to obtain a modified manganese-based powder catalyst. The surfactant was hexadecyltrimethylammonium bromide (CTAB); the manganese source was manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5), and the manganese source concentration was 0.4 mol / L; the transition metal precursor was ferric nitrate, and the molar ratio of manganese to iron in the impregnation solution was 2:1.

[0056] (3) Add 5 mg of the modified manganese-based powder catalyst obtained in step (2), 0.005 mL of polytetrafluoroethylene emulsion, 0.025 mL of water and 0.47 mL of ethanol into a sample tube, and obtain a slurry by ultrasonication. Then, drop the slurry on the pretreated substrate material obtained in step (1), and dry it to obtain a modified manganese-based material.

[0057] Embodiment 5:

[0058] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0059] The preparation method is the same as that of Example 4, except that the transition metal precursor in step (2) is changed to ferric sulfate to obtain a modified manganese-based material.

[0060] Embodiment 6:

[0061] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0062] The preparation method is the same as that of Example 4, except that the transition metal precursor in step (2) is changed to ferric chloride to obtain a modified manganese-based material.

[0063] Embodiment 7:

[0064] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0065] The preparation method is the same as that of Example 4, except that the surfactant in step (2) is changed to sodium dodecyl sulfate (SDS) to obtain a modified manganese-based material.

[0066] Embodiment 8:

[0067] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0068] The preparation method is the same as that of Example 4, except that the surfactant in step (2) is changed to Tween 80 to obtain a modified manganese-based material.

[0069] Embodiment 9:

[0070] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0071] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0072] (2) 80 mL of the impregnation solution containing the manganese source, transition metal precursor and surfactant was placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal kettle and hydrothermaled at 120°C for 2 hours. After cooling, it was washed and dried to obtain a modified manganese-based powder catalyst. The impregnation solution was prepared by the following method: a surfactant was added to 80 mL of deionized water at a concentration of 2 g / L, and then a manganese source and a transition metal precursor were added and ultrasonically mixed to obtain a modified manganese-based powder catalyst. The surfactant was sodium dodecyl sulfate; the manganese source was manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5) at a concentration of 0.4 mol / L; the transition metal precursor was ferric nitrate, and the molar ratio of manganese to iron in the impregnation solution was 2:1.

[0073] (3) Add 5 mg of the modified manganese-based powder catalyst obtained in step (2), 0.005 mL of polytetrafluoroethylene emulsion, 0.025 mL of water and 0.47 mL of ethanol into a sample tube, and obtain a slurry by ultrasonication. Then, drop the slurry on the pretreated substrate material obtained in step (1), and dry it to obtain a modified manganese-based material.

[0074] Embodiment 10-13:

[0075] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0076] The preparation method is the same as that of Example 9, except that the molar ratio of manganese to iron in the impregnation solution in step (2) is modified to 1:1, 1:2, 1:4 and 4:1, respectively, to obtain a modified manganese-based material.

[0077] Embodiment 14-16:

[0078] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0079] The preparation method is the same as that of Example 9, except that the hydrothermal temperature in step (2) is modified to 100° C., 140° C. and 160° C. in sequence to obtain a modified manganese-based material.

[0080] Comparative Example 1:

[0081] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0082] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0083] (2) 80 mL of the impregnation solution containing the manganese source and the transition metal precursor is placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal autoclave and hydrothermaled at 120°C for 2 hours. After cooling, it is washed and dried to obtain a modified manganese-based powder catalyst. The impregnation solution is prepared by the following method: a manganese source and a transition metal precursor are added to 80 mL of deionized water and ultrasonically mixed to obtain a modified manganese-based powder catalyst. The manganese source is manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5), with a concentration of 0.4 mol / L; the transition metal precursor is ferric nitrate, and the molar ratio of manganese to iron in the impregnation solution is 2:1.

[0084] (3) Add 5 mg of the modified manganese-based powder catalyst obtained in step (2), 0.005 mL of polytetrafluoroethylene emulsion, 0.025 mL of water and 0.47 mL of ethanol into a sample tube, and obtain a slurry by ultrasonication. Then, drop the slurry on the pretreated substrate material obtained in step (1), and dry it to obtain a modified manganese-based material.

[0085] Comparative Example 2:

[0086] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0087] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0088] (2) 80 mL of the impregnation solution containing the manganese source and the surfactant was placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal kettle and hydrothermaled at 120°C for 2 hours. After cooling, it was washed and dried to obtain a modified manganese-based powder catalyst. The impregnation solution was prepared by the following method: a surfactant was added to 80 mL of deionized water at a concentration of 2 g / L, and then a manganese source was added and ultrasonically mixed to obtain a modified manganese-based powder catalyst. The surfactant was sodium dodecyl sulfate; the manganese source was manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5) at a concentration of 0.4 mol / L.

[0089] (3) Adding the modified manganese-based powder catalyst obtained in step (2), polytetrafluoroethylene emulsion, water and ethanol into the sample tube, ultrasonically obtaining a slurry, and then dropping the slurry onto the pretreated substrate material obtained in step (1), drying, and obtaining a modified manganese-based material.

[0090] Comparative Example 3:

[0091] A method for preparing a modified manganese-based material for sewage treatment comprises the following steps:

[0092] (1) The graphite felt was stirred and washed in a 3 mol / L nitric acid solution for 12 h, then washed with deionized water until neutral, and finally dried at a constant temperature of 80° C. for 6 h to obtain a pretreated substrate material.

[0093] (2) 80 mL of the impregnation solution containing the manganese source is placed in a polytetrafluoroethylene liner, and then placed in a hydrothermal kettle and hydrothermaled at 120°C for 2 hours, and washed and dried after cooling to obtain a modified manganese-based powder catalyst. The impregnation solution is prepared by the following method: a manganese source is added to 80 mL of deionized water and ultrasonically mixed to obtain a manganese source; the manganese source is manganese sulfate monohydrate and potassium permanganate (molar ratio of 1:1.5), and the concentration is 0.4 mol / L.

[0094] (3) Add 5 mg of the modified manganese-based powder catalyst obtained in step (2), 0.005 mL of polytetrafluoroethylene emulsion, 0.025 mL of water and 0.47 mL of ethanol into a sample tube, and obtain a slurry by ultrasonication. Then, drop the slurry on the pretreated substrate material obtained in step (1), and dry it to obtain a modified manganese-based material.

[0095] Experimental Example 1: Effects of different transition metal elements on the properties of modified manganese-based materials

[0096] The modified manganese-based materials prepared in Examples 1-3 were used for experiments. 60 mL of 200 mg / LRh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based electrode material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 1 shown.

[0097] Depend on Figure 1 It can be seen that the three modified manganese-based metal materials prepared in Examples 1-3 can degrade rhodamine B more efficiently, among which MnFeO xThe material has the best degradation performance, which can reach 100%. The main reason is that iron ions play a key role in water treatment. Iron ions act as catalysts in the electro-Fenton reaction and can effectively oxidize and decompose organic pollutants. Their catalytic performance depends on the reducing ability of iron ions and the generated hydroxyl radicals (·OH). In addition, other reasons include: (1) Oxidation ability. Ferric nitrate can release more hydroxyl radicals in the electro-Fenton process and has strong oxidation ability, which helps the degradation of organic matter. (2) Reduction ability: Iron ions are easier to reduce in the electro-Fenton process and can more effectively promote the reaction. (3) Stability: Ferric nitrate is relatively stable in solution and is not easily oxidized, thus ensuring the continuity of the catalytic process.

[0098] Experimental Example 2: Effects of different iron salts as transition metal precursors on the properties of modified manganese-based materials

[0099] The modified manganese-based materials prepared in Examples 4-6 were used for experiments. 60 mL of 200 mg / LRh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based electrode material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 2 shown.

[0100] Depend on Figure 2 It can be seen that the three modified manganese-based materials obtained in Examples 4-6 can all efficiently degrade Rhodamine B, among which the electrode material with ferric nitrate as the iron source has the best degradation performance, which can reach 97% in 2.5h. The main reason is that ferric nitrate has good solubility in water, which means that it can more easily contact with reactants during the catalytic process, thereby improving the catalytic efficiency. In addition, the molecular structure of ferric nitrate is relatively stable and is not prone to hydrolysis or other side reactions, which allows it to stably exist in a wider pH range, and can more effectively participate in the reaction during the catalytic process, thereby efficiently degrading organic pollutants.

[0101] Experimental Example 3: Effects of different surfactants on the properties of modified manganese-based materials

[0102] The modified manganese-based materials prepared in Example 4, Example 7-8 and Comparative Example 1 were used for experiments. 60 mL of 200 mg / L Rh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 3 shown.

[0103] Depend on Figure 3 It can be seen that the electrode material prepared by adding SDS has higher activity than the electrode material prepared by other surfactants, and the degradation rate of rhodamine B can reach 98% in 2.5h. x The degradation effect is 73% in 2.5h, which is lower than that of the electrode materials with the addition of three surfactants. Therefore, it can be determined that the improvement in the degradation effect is the result of adding surfactants. This is because surfactants can change the physicochemical properties of the metal surface, increase the specific surface area of ​​the material, increase the active sites, and thus promote the electro-Fenton degradation effect. In addition, SDS, CTAB, and Tween 80 are anionic, cationic, and nonionic surfactants, respectively, and anionic surfactants have the following advantages: (1) Anionic surfactants can improve the interfacial stability between the electrode material and the electrolyte, reduce the interfacial impedance, and facilitate the charge transfer reaction; (2) Anionic surfactant molecules can form aggregates on the metal surface, thereby increasing the number of active sites, which is conducive to the catalytic reaction; (3) Anionic surfactants can improve the charge transfer process between the electrode and the electrolyte, reduce the charge transfer resistance, and improve the electrocatalytic efficiency. (4) Some anionic surfactants can change the surface morphology of metal materials, such as forming a uniform nanostructure, which helps to improve the electrocatalytic performance. Therefore, SDS is the best surfactant of the present invention.

[0104] Experimental Example 4: Effects of different ratios of manganese and transition metals on the properties of modified manganese-based materials

[0105] The modified manganese-based materials prepared in Examples 9-13 were used for experiments. 60 mL of 200 mg / LRh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based electrode material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 4 shown.

[0106] Depend on Figure 4 It can be seen that Fe 3+ The modified manganese-based electrode materials obtained after addition can achieve a high electro-Fenton degradation effect on Rhodamine B, and can completely degrade 200 mg / L Rh B within 4 hours. When the molar ratio of Mn to Fe is 1:2, the degradation efficiency of Rh B is faster. The reason may be that Fe 3+ Addition can promote the cyclic transformation of various valence states of Mn. At the same time, the electron transfer between different valence states of Mn and Fe can also promote oxygen reduction to produce H2O2, thereby generating more active free radicals to efficiently degrade Rh B. With the increase of Fe content, the ability of the material to produce H2O2 and active free radicals is improved, and the electro-Fenton degradation efficiency is increased, but too much will lead to a weakened selectivity of H2O2, which cannot be effectively utilized and the catalytic degradation effect is weakened. Therefore, the optimal manganese-iron molar ratio is 1:2.

[0107] Experimental Example 5: Effect of different hydrothermal temperatures on the properties of modified manganese-based materials

[0108] The modified manganese-based materials prepared in Example 9 and Examples 14-16 were used for experiments. 60 mL of 200 mg / LRh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based electrode material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 5 shown.

[0109] Depend on Figure 5 It can be seen that when the hydrothermal temperature during preparation is increased to 120°C, the degradation rate of Rh B can reach 93% in 2h. When the hydrothermal temperature is further increased, the degradation efficiency of Rh B gradually weakens. This indicates that the collapse of the material structure above 140°C hinders the degradation of MnFeO x -The rate of H2O2 production and electron transfer of the SDS cathode in the electro-Fenton process; therefore, 120°C is selected as the optimal hydrothermal temperature for preparing the modified manganese-based material in the present invention.

[0110] Experimental Example 6: Characterization of Physical and Chemical Properties

[0111] The modified manganese-based materials prepared in Example 11 and Comparative Examples 1-3 were used for experiments. 60 mL of 200 mg / LRh B solution was placed in a 100 mL electrolytic cell, and a 0.5 mol / L H2SO4 solution was used to adjust the pH (3-5). An air pump (flow rate 1 L / min) was used to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. A two-electrode system with a Pt sheet as the anode and a modified manganese-based electrode material as the cathode, with a distance of 2 cm between the two electrodes, was used to degrade Rh B under constant voltage conditions using DC voltage regulation. The degradation effect is shown in FIG. Figure 6 shown.

[0112] Depend on Figure 6 It can be seen that the electro-Fenton degradation rates of Rh B by the modified manganese-based materials prepared in Comparative Example 3, Comparative Example 2, Comparative Example 1 and Example 11 are 65%, 72%, 81% and 100% respectively in 4 hours. The main reason is that the surfactant and Fe 3+ The addition of promotes the production of manganese oxides in various valence states, increases the specific surface area of ​​the material, improves the hydrophilicity of the material, increases the H2O2 selectivity, and promotes the electro-Fenton degradation performance.

[0113] In order to further verify the mechanism of improving the electro-Fenton degradation effect, the electrode materials prepared in Example 11 and Comparative Examples 2-3 were characterized and analyzed by SEM, XRD and contact angle tests. Figure 7-Figure 9 The three electrode materials were tested for H2O2 selectivity and electron transfer number using the RRDE three-electrode system. The experimental results are shown in Fig.10 As shown. According to the method in Experimental Example 1, a two-electrode system was constructed to degrade the same concentration of rhodamine B, methylene blue, methyl orange, malachite green, and nitrogen methyl oxide morpholine. The TOC degradation results are shown in Fig.11 As shown. And stability test and quenching experiment were carried out, the results are as follows Figure 12-13 The free radicals generated during the electro-Fenton degradation process of the material prepared in Example 11 were subjected to EPR testing, and the results are shown in Fig.14 shown.

[0114] Depend on Figure 7 From the SEM images, it can be seen that the surface morphology of the material prepared in Comparative Example 3 is blocky, and as the surfactant and Fe 3+ The addition of , the block becomes smaller, the specific surface area increases, comparative example 3, comparative example 2 and example 11 are 37.191, 54.386, 207.74m 2 / g. By Figure 8 The XRD results also show that the surfactant and Fe 3+ The addition of promoted the production of manganese oxides with various valence states, and the hydrophilicity was also significantly improved ( Fig. 9 ), promoting electron transfer in the oxygen reduction reaction.

[0115] Depend on Fig.10 It can be seen that within the voltage range of -0.15V to 0.3V, the H2O2 selectivity of the modified manganese-based electrode material prepared in Example 11 can reach more than 90% (the H2O2 selectivity of Comparative Example 3 is 40%), and the oxygen reduction reaction that occurs is closer to 2e - This result corresponds to the fact that the electro-Fenton degradation performance of Rh B can reach 100% (the degradation rate of Rh B of pure manganese oxide is up to 65%). In addition, the modified manganese-based electrode material prepared in Example 11 can degrade the same type of organic wastewater ( Fig.11 ), the electro-Fenton TOC degradation rate can reach more than 84%, and the stability is good ( Fig.12 ), the degradation rate can still reach 100% after 4 cycles. The results of the quenching experiment of reactive oxygen species (ROS) during the EF reaction ( Fig.13 ) shows that isopropanol has the greatest inhibitory effect on the degradation of Rh B (40.33%), indicating that the degradation of Rh B is mainly caused by the generated ·OH. The EPR test results for ·OH ( Fig.14 ) also has an obvious 1:2:2:1 quartet peak. And p-benzoquinone also has a certain inhibitory effect on the degradation rate of Rh B (88.5%), indicating that O2 - Another effective reactive oxygen species produced during the heterogeneous EF process also plays an important role in the degradation of Rh B.

[0116] Experimental Example 7: NMMO wastewater treatment experiment

[0117] The modified manganese-based material prepared in Example 11 was used in the treatment of organic wastewater containing nitrogenmethylmorpholine oxide (NMMO), one of the actual morpholine derivatives. The mass fractions of NMMO in the wastewater were 2.40%, 3.12%, 5.71%, 8.30% and 9.23%, respectively.

[0118] Take 60mL of NMMO solution with different mass fractions in a 100mL electrolytic cell, use 0.5mol / L H2SO4 solution to adjust the pH (3-5), and use an air pump (flow rate 1L / min) to ventilate the electrolyte to increase the dissolved oxygen concentration in the electrolyte. x -SDS was used as the cathode, and the two electrodes were in a two-electrode system with a distance of 2 cm between the two electrodes. DC voltage regulation was used to degrade NMMO under constant voltage conditions. The degradation effect is as follows Fig.15 shown.

[0119] Depend on Fig.15It can be seen that the modified manganese-based electrode material prepared in Example 11 has a good electro-Fenton degradation effect on NMMO wastewater with different mass fractions, up to 99%. The reason is that the modified manganese-based electrode material produces free hydroxyl radicals (·OH) during the wastewater treatment process, which is a very powerful oxidant that can destroy the macromolecular structure in NMMO and degrade it into simple inorganic substances. In addition, the surfactant added to the material can also enhance the generation rate of hydroxyl radicals and improve the electro-Fenton degradation performance. As the mass fraction of NMMO increases, the degradation rate decreases because the high mass fraction of NMMO wastewater makes the current distribution inside the reaction tank uneven, resulting in a decrease in the electrochemical oxidation efficiency of some reaction areas.

[0120] Experimental Example 8: EDTA-Ni wastewater treatment experiment

[0121] The modified manganese-based material prepared in Example 11 was used in actual EDTA-Ni wastewater treatment research.

[0122] Take 60mL EDTA-Ni wastewater (COD≈1000mg / L, Ni 2+ Content ≈ 0.66mg / L) in a 100mL electrolytic cell, use 0.5mol / L H2SO4 solution to adjust pH (3-5), use an air pump (flow rate 1L / min) to pass air into the electrolyte to increase the dissolved oxygen concentration in the electrolyte. x -SDS was used as the cathode and the two-electrode system with a distance of 2 cm between the two electrodes was used to degrade EDTA-Ni wastewater under constant pressure conditions using DC voltage regulation.

[0123] The modified manganese-based material prepared in Example 11 has a good electro-Fenton degradation effect on EDTA-Ni wastewater, with an EDTA removal rate of up to 99.2%, a COD removal rate of 89%, and a Ni 2+ The removal rate of the catalyst is 85%. 2+ The adsorption capacity reaches 287 mg / g.

[0124] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified manganese-based material for sewage treatment, characterized in that: The following steps are involved: (1) washing the three-dimensional substrate material in an acidic solution and deionized water in sequence, and drying, to obtain a pretreated substrate material; (2) mixing a manganese source, a transition metal precursor and a surfactant in an aqueous solution, performing a hydrothermal reaction, and drying to obtain a modified manganese-based powder catalyst; (3) Prepare a modified manganese-based powder catalyst slurry, drop it on the pretreated base material, and dry it to obtain the catalyst.

2. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: In the step (1), the three-dimensional substrate material is graphite felt, carbon felt, porous carbon or activated carbon fiber; the acidic solution is nitric acid solution with a concentration of 1-3 mol / L.

3. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: In the step (1), the washing time in the acidic solution is 12-16 hours, and the washing in deionized water is neutral; the drying temperature is 60-90° C. and the drying time is 4-8 hours.

4. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: In step (2), the manganese source is one of manganese sulfate, potassium permanganate, manganese chloride and manganese nitrate; the transition metal precursor is at least one of iron, cobalt and nickel metal salts; and the surfactant is at least one of stearic acid, oleic acid, lauric acid, sodium dodecyl sulfate, hexadecyltrimethylammonium chloride, sodium dodecyl sulfonate, long-chain alkyl amino acid and Tween 80.

5. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: In the step (2), the concentration of the surfactant in the aqueous solution after mixing is 2-10 g / L; the molar ratio of manganese to transition metal is 1:1-8:1, and the concentration of manganese in the aqueous solution is 0.1-0.5 mol / L.

6. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (2) is 80-180° C. and the time is 2-12 hours.

7. The method for preparing a modified manganese-based material for sewage treatment according to claim 1, characterized in that: The manganese-based powder catalyst slurry in step (3) is prepared by the following method: modified manganese-based powder catalyst, polytetrafluoroethylene emulsion, water and ethanol are mixed and ultrasonically prepared.

8. A modified manganese-based material for sewage treatment, characterized in that: The method is prepared by the preparation method according to any one of claims 1 to 7.

9. The modified manganese-based material for sewage treatment according to claim 8 is used in organic wastewater from degradation of dyes, chemical nickel plating and morpholine derivatives.

Images