CN108033522B - An Electrocatalytic Coupled Advanced Oxidation System - Google Patents

Abstract

The invention provides an electrocatalytic coupling advanced oxidation system which can degrade organic pollutants into carbon dioxide and synchronously electrocatalytic reduce the carbon dioxide into hydrocarbons. In the catalytic system, three-dimensional hexagonally-star-shaped Co₃O₄And nanosheet stacked flower-shaped CuO are respectively used as anode and cathode materials, and the two electrode materials are prepared by a solvothermal method. In a three-electrode system electrocatalytic process, Co₃O₄The electric anode can completely mineralize the p-nitrophenol into CO₂And H₂O, CuO cathodes can simultaneously reduce the carbon dioxide produced to useful hydrocarbons. When the external bias is-0.8V vs Ag/AgCl, the catalytic effect of the material is the best. The removal rate of the p-nitrophenol can reach more than 98 percent, and the yield of the methanol and the yield of the ethanol respectively reach 49.145 and 20.475 micromoles/liter/hour.

Description

An Electrocatalytic Coupled Advanced Oxidation System

technical field

The invention relates to an electrocatalytic coupled advanced oxidation system, which belongs to the field of sewage treatment.

Background technique

The rapid development of industrialization and urbanization has brought highly developed material civilization to human beings, but also brought serious problems such as environmental pollution and resource shortage that cannot be ignored. The ever-increasing pollution will not only cause serious problems like global warming, but will also threaten our lives. Among them, the large amount of industrial wastewater discharge and the large amount of CO ₂ produced by the combustion of fossil energy are of particular concern. At present, water environment pollutants are not only simple inorganic pollutants, but more and more complex components, and the problem of organic pollution with higher and higher concentrations is becoming more and more serious. How to deal with these highly concentrated, refractory and easily accumulated organic pollutants harmful to human beings and how to reduce the emission of greenhouse gas CO ₂ has become the focus of the society. The common treatment methods of organic pollutants include photocatalysis, electrocatalysis, advanced oxidation technology and traditional physical and chemical methods. However, these methods can mineralize organic pollutants into CO ₂ , but there are still low quantum efficiency, The problems of low energy utilization rate and difficult recovery of catalysts. On the other hand, reports of the catalytic reduction of _CO2 to other hydrocarbons have been extensively studied, and common approaches for the catalytic reduction of _CO2 include photocatalysis, electrocatalysis, and photoelectrocatalytic methods, etc., with low Faradaic efficiency and selectivity of reduction products. Such issues are still urgently needed to be addressed, although there are numerous reports on the removal of organic pollutants as well as the reduction of _CO2 . However, at the same time, all the current treatment methods have not considered the catalytic reduction of _CO2 with the efficient removal of organic pollutants. This not only solves the problem of environmental pollution, but also realizes the resource utilization of organic pollutants, and overcomes the negative effects of greenhouse gases while solving organic pollutants in water bodies.

In recent years, advanced oxidation technologies (AOPs) based on sulfate radicals (SO ₄ ·-) and hydroxyl radicals (·OH) have developed rapidly and become emerging technologies for efficient treatment of organic pollutants. There have been a lot of reports on the activation of peroxymonosulfate (PMS) or peroxodisulfate (PDS) to generate SO ₄ ·- and ·OH to remove organic pollutants. It mainly includes the following categories: (1) Ultrasonic, heating, UV light; (2) Variable valence metal ions in the homogeneous catalysis process: Co ²⁺ , Mn ²⁺ , Fe ²⁺ , etc.; (3) Contains variable valence metals Heterogeneous catalysts: Co ₃ O ₄ , MnO ₂ , Fe ₂ O ₃ , etc. Shiying Yang et al. systematically discussed the degradation of acid orange-7 by UV light and PMS activation under heating conditions to generate sulfate radicals and hydroxyl radicals. Jing Deng obtained ordered mesoporous Co ₃ O ₄ by template method, which has higher stability than Co ₃ O ₄ nanoparticles, and explored the mechanism of its activation of PMS to degrade chloramphenicol. At the same time, electrocatalytic removal of organic pollutants has attracted extensive attention of researchers, from the early simple anodic oxidation removal of organic pollutants to the application of electro-Fenton to organic wastewater. Comninellis, C. Electrocatalytic oxidation of phenol by doped _SnO2 as anode, TOC removal can reach 90%, and the process of oxidation of phenol to _CO2 was confirmed by analyzing the intermediate products of the reaction as well as the balance of carbon. Although there are many reports on electrocatalytic oxidation and SO ₄ ·-based advanced oxidation to remove organic pollutants, there are also many reports on electrocatalytic reduction of CO ₂ into organic compounds. However, there is no report on the system of electrocatalytic coupled advanced oxidation degradation of organic pollutants to carbon dioxide and simultaneous electrocatalytic reduction to hydrocarbons. Therefore, it is urgent to fabricate a novel electrocatalytic system to experiment with these two goals. This is not only conducive to environmental governance, but also to alleviate the energy crisis, and at the same time provides new ideas for environmental governance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an electrocatalytic coupled advanced oxidation system, in particular to a novel coupled electrocatalytic method and a new electrode material preparation scheme, which provides new ideas and new materials for solving today's pollution and energy problems.

One aspect of the present invention provides an electrocatalytic coupled advanced oxidation system in which _three -dimensional hexagonal star-like Co3O4 and nanosheet _- stacked flower-like CuO are used as anode and cathode materials, respectively.

According to the present invention, the advanced oxidation technology is coupled with electrocatalysis at the anode, and the Co ₃ O ₄ anode can not only activate persulfate to generate sulfate radicals and hydroxyl radicals, but also generate hydroxyl radicals through electrocatalysis, so as to efficiently Organic pollutants are thoroughly mineralized to _CO2 and _H2O .

According to the present invention, the _CO2 produced by the thorough mineralization of organic pollutants at the anode is introduced into the cathode through the exhaust pipe, and then reduced to hydrocarbons on the CuO cathode.

According to the present invention, both electrode materials are prepared by solvothermal method.

Another aspect of the present invention provides a method for synthesizing three-dimensional hexagonal star-shaped Co ₃ O ₄ and nano-sheet stacked flower-shaped CuO electrode materials.

Another aspect of the present invention provides an application method of the electrocatalytic coupled advanced oxidation system and its application in the field of sewage treatment.

The advantages of the present invention are: 1. The catalyst of the present invention can also reduce carbon dioxide into green chemical energy-hydrocarbon fuel while degrading organic pollutants; 2. The present invention removes the organic pollution that is harmful to the environment through electrocatalysis coupled with advanced oxidation technology 3. In the present invention, the target catalyst is grown on the conductive glass substrate in situ by a one-step solvothermal method, and the new urea is regulated and synthesized by adding different urea. appearance. 4. The catalyst of the present invention is stable, easy to recover, and has good catalytic effect; 5. The material of the present invention is cheap and easy to obtain, the synthesis method is simple, the synthesis yield and purity are high, the experiment repeatability is good, and it is suitable for the requirements of scaled production

Description of drawings

Fig. 1 is the Co0.5 catalyst before and after the reaction of the present invention and pure Co ₃ O ₄ and with Co0.2, Co1.0 and Co1.5 X-ray powder diffraction comparison diagram;

Fig. 2 is the CuO catalyst of the present invention and pure CuOX ray powder diffraction contrast figure;

Fig. 3 is the scanning electron microscope picture of Co ₃ O ₄ catalyst of the present invention;

Fig. 4 is the scanning electron microscope picture of CuO catalyst of the present invention;

Fig. 5 Co ₃ O ₄ of the present invention degrades the rate of p-nitrophenol in the advanced oxidation process and the rate of Co0.5 electrocatalytic oxidation to degrade p-nitrophenol;

Fig. 6 Co0.5 of the present invention degrades the rate of p-nitrophenol in the process of electrocatalytic oxidation coupled with advanced oxidation;

Fig. 7 Co0.5 electric anode and CuO electric cathode of the present invention degrade p-nitrophenol and reduce carbon dioxide to methanol ethanol under different voltages;

Fig. 8 is a UV-Vis full-band image of the Co0.5 catalyst of the present invention in the electrocatalytic coupled advanced oxidation degradation of p-nitrophenol for 1 hour.

Detailed ways

One aspect of the present invention provides an electrocatalytic coupled advanced oxidation system in which _three -dimensional hexagonal star-like Co3O4 and nanosheet _- stacked flower-like CuO are used as anode and cathode materials, respectively.

Preferably, the advanced oxidation technology is coupled with electrocatalysis at the anode, and the Co ₃ O ₄ anode can not only activate persulfate to generate sulfate radicals and hydroxyl radicals, but also generate hydroxyl radicals through electrocatalysis, so as to efficiently convert organic The pollutants are thoroughly mineralized to _CO2 and _H2O .

Preferably, the _CO2 produced by the thorough mineralization of organic pollutants at the anode is introduced into the cathode through the exhaust pipe, and then reduced to hydrocarbons at the CuO cathode.

Another aspect of the present invention provides a method for synthesizing three-dimensional hexagonal star-shaped Co ₃ O ₄ and nano-sheet stacked flower-shaped CuO electrode materials.

Preferably, both electrode materials are prepared by solvothermal method.

Preferably, the synthesis method of the three-dimensional hexagonal star-shaped Co ₃ O ₄ material is as follows: dissolve 0.5-1 g of cobalt nitrate in 40 ml of a mixed solution of ethylene glycol and water and stir, and after complete dissolution, add 0.5-1.5 g of urea and stir evenly, Then add 30-50 mg of cetyltrimethylammonium bromide and 1-2 g of ammonium fluoride, stir at room temperature for 30-45 minutes to form a uniform, transparent colorless solution, transfer the solution to 100 ml of polytetrafluoroethylene In the lining of the vinyl fluoride reactor. Then, place a piece of cleaned conductive glass (1.5 cm × 4.0 cm) in the reactor tilted, with the conductive surface of the conductive glass facing up, and finally transfer the reactor to a drying oven for reaction at 100-120 °C, and conduct the reaction for 10-12 hours. A purple precursor is obtained on the glass. The conductive glass is put into a muffle furnace, calcined at 350 DEG C to 550 DEG C for 2 to 4 hours, and then cooled to room temperature to obtain three-dimensional hexagonal star-shaped Co ₃ O ₄ .

Preferably, the characteristics of the synthesis method of nanosheet stacked flower-like CuO material are: take 5-6 grams of sodium hydroxide, 1-1.2 grams of ammonium persulfate and 0.2-0.4 of sodium tungstate and dissolve them in 30-40 ml of deionized water in turn , and stir for 30 to 45 minutes at room temperature to form a uniform and transparent colorless solution. Then 0.4-0.6 g of sodium dodecyl sulfate was added to the above solution to form a homogeneous white solution. After the sodium dodecyl sulfate was completely dissolved, it was transferred into a polytetrafluoroethylene-lined stainless steel autoclave, and the cleaned copper mesh (1.5 cm×4.0 cm) was immersed in the above solution. Under the closed condition of the autoclave, the reaction was carried out at 100-150° C. for 24 hours, then cooled to room temperature, and the copper mesh was taken out and washed with deionized water to obtain black nano-sheet stacked flower-like CuO.

The invention also provides an application method of an electrocatalytic coupled advanced oxidation system. In a conventional H-type electrolytic cell reaction system, three-dimensional hexagonal star-shaped Co ₃ O ₄ and nano-sheet stacked flower-shaped CuO are used as anode and cathode materials respectively, Add 0.1 mol/L sodium sulfate solution to the anode compartment, add 0.1 mol/L potassium bicarbonate solution to the cathode compartment, then add 0.5 g/L persulfate and 10 mg/L p-nitrophenol solution to the anolyte, Electrolysis and advanced oxidation coupled reactions are carried out by electrification.

Preferably, the volumes of the 0.1 mol/L sodium sulfate solution added to the anode compartment and the 0.1 mol/L potassium bicarbonate solution added to the cathode compartment are both 60 ml.

The present invention also provides an application of an electrocatalytic coupled advanced oxidation system in the field of sewage treatment, for removing organic pollutants in the wastewater, the organic pollutants are mineralized at the anode to generate CO ₂ and introduced into the cathode through an exhaust pipe , which are then reduced to hydrocarbons at the cathode.

The following examples further illustrate the present invention, but do not limit the present invention accordingly.

Example 1

Synthesis of 3D Hexagonal Star _- shaped _Co3O4 Electroanode Materials:

Dissolve 0.582 g of cobalt nitrate (2 mmol) in 10 ml of ethylene glycol and 30 ml of water and stir. After it is completely dissolved, add 0.5 g of urea and stir evenly. Then add 0.05 g of cetyltrimethylammonium bromide and 1.455 g of fluoride. ammonium, stirred at 25°C for 30 minutes to form a uniform, transparent, colorless solution, which was transferred to a 100-ml polytetrafluoroethylene reactor liner. Afterwards, place a piece of cleaned conductive glass (1.5 cm × 4.0 cm) inclined in the reactor, with the conductive surface of the conductive glass facing up, and finally transfer the reactor to a drying oven at 120 °C for reaction, and the conductive glass will get purple after 12 hours of reaction. precursor. The conductive glass was put into a muffle furnace, pre-calcined at 350° C. for 2 hours, then calcined at 550° C. for 2 hours, and then cooled to room temperature to obtain Co ₃ O ₄ . Here, the Co ₃ O ₄ obtained by adding urea in amounts of 0.2 g, 0.5 g, 1.0 g and 1.5 g are named as Co0.2, Co0.5, Co1.0 and Co1.5 electrodes.

Example 2

Synthesis of nanosheet stacked flower-like CuO electric cathode: Dissolve 6.4 g of sodium hydroxide, 1.0954 g of ammonium persulfate and 0.211 g of sodium tungstate in turn in 32 ml of deionized water, and stir at 25 °C for 30 minutes to form a uniform, transparent colorless solution. Then 0.4614 g of sodium dodecyl sulfate was added to the above solution to form a homogeneous white solution. After the sodium dodecyl sulfate was completely dissolved, it was transferred into a polytetrafluoroethylene-lined stainless steel autoclave, and the cleaned copper mesh (1.5 cm×4.0 cm) was immersed in the above solution. Under the closed condition of the autoclave, the reaction was carried out at 130 °C for 24 hours, then cooled to room temperature, and the copper mesh was taken out and washed with deionized water to obtain a black sample CuO.

As shown in Figure 1-Figure 8, the X-ray powder diffraction test results show that:

The diffraction patterns of a series of Co0.2, Co0.5, Co, 1.0 and Co1.5 catalysts of the present invention are completely consistent with those of the standard card Co ₃ O ₄ , indicating that the addition of different amounts of urea does not affect the crystallinity of Co ₃ O ₄ , and the crystal form did not change after the reaction. Raman analysis, XPS and EDS analysis show that the invented Co0.5 catalyst material is composed _{of Co3O4} composite. From the scanning electron microscope, it can be seen that the addition of different amounts of urea has a great influence on the morphology of the catalyst Co0.5. When the urea is less than 0.5, the catalyst morphology has a flower-like structure composed of nanoparticles. When the urea is greater than 0.5, the surface becomes smooth, and the morphology is further transformed into a hexagonal star flower-like structure.

The CuO of the present invention can be seen from the scanning electron microscope, and the morphology of the CuO is a flower-like structure stacked by nano-sheets. From the linear cyclic voltammetry curve, it can be found that the CuO catalyst of the present invention has high activity for carbon dioxide reduction.

Example 3

In a conventional H-type electrolytic cell reaction system, three-dimensional hexagonal star-like Co ₃ O ₄ and nano-sheet stacked flower-like CuO were used as anode and cathode materials, respectively, and 0.1 mol/L sodium sulfate solution (with a volume of 60 mol/L) was added to the anode chamber. mL), add 0.1 mol/L potassium bicarbonate solution (volume 60 mL) in the cathode compartment, then add 0.5 g/L persulfate and 10 mg/L p-nitrophenol solution to the anolyte, and electrify for electrolysis coupled with advanced oxidation reactions.

When the applied bias voltage is -0.8V vs Ag/AgCl, the removal rate of p-nitrophenol by the Co ₃ O ₄ electric anode can reach more than 98%, and the CuO electric cathode can simultaneously reduce carbon dioxide to methanol and ethanol with a yield of 49.145%, respectively. and 20.475 μmol/L/hr. It can be confirmed that the Co _0.5 catalyst of the present invention can mineralize p-nitrophenol into CO ₂ and H ₂ O through the full-band degradation data.

The catalysts of the invention are all prepared by a solvothermal method, the materials are cheap and easy to obtain, the synthesis method is simple, the synthesis yield is high, the purity is also high, and the repeatability is good, and is suitable for the requirements of enlarged production. The catalyst of the present invention is coupled with electrocatalytic oxidation technology and electrocatalytic reduction technology, and at the same time, coupled with electrocatalytic oxidation technology and advanced oxidation, effectively mineralizes organic pollutants in water bodies and simultaneously converts carbon dioxide into simple and useful chemical products (such as methane, methanol, ethanol, etc.) as the target. The electrocatalyst of the invention can efficiently remove organic pollutants and convert carbon dioxide into green energy, which is not only conducive to environmental governance, but also helps to alleviate energy crisis, and provides a new idea for environmental governance.

The above contents are only preferred embodiments of the present invention. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (4)

1. an electrocatalytic coupling advanced oxidation system is characterized in that: in this system, three-dimensional hexagonal star-shaped Co ₃ O ₄ and nano-sheet stacking flower-shaped CuO are respectively used as anode and cathode material; Catalytic coupling, the Co ₃ O ₄ electroanode can not only activate persulfate to generate sulfate radicals and hydroxyl radicals, but also generate hydroxyl radicals through electrocatalysis, so as to efficiently and thoroughly mineralize organic pollutants into CO ₂ and H ₂ O; where: _CO2 produced by the thorough mineralization of organic pollutants at the anode is introduced into the cathode through the exhaust pipe, and then reduced to hydrocarbons on the CuO cathode; Both electrode materials were prepared by solvothermal method; The method for synthesizing the three-dimensional hexagonal star-shaped Co ₃ O ₄ material is as follows: dissolving 0.5-1 g of cobalt nitrate in 40 ml of a mixed solution of ethylene glycol and water, and stirring, after completely dissolving, adding 0.5-1.5 g of urea and stirring evenly; Add 30-50 mg of cetyltrimethylammonium bromide and 1-2 g of ammonium fluoride, stir at room temperature for 30-45 minutes to form a uniform, transparent colorless solution, transfer the solution to 100 ml of polytetrafluoroethylene The ethylene reactor is lined; then a piece of cleaned conductive glass is placed in the reactor obliquely, with the conductive surface of the conductive glass facing up, and finally the reactor is transferred to a drying oven for reaction at 100-120 °C, and the reaction is conducted for 10-12 hours. A purple precursor is obtained on the glass; the conductive glass is put into a muffle furnace, calcined at 350°C to 550°C for 2 to 4 hours, and then cooled to room temperature to obtain a three-dimensional hexagonal star-shaped Co ₃ O ₄ ; The method for synthesizing the nanosheet stacked flower-like CuO material is as follows: take 5-6 grams of sodium hydroxide, 1-1.2 grams of ammonium persulfate and 0.2-0.4 of sodium tungstate and dissolve them in 30-40 milliliters of deionized water in turn, and at room temperature Stir for 30 to 45 minutes to form a uniform and transparent colorless solution; then add 0.4 to 0.6 g of sodium dodecyl sulfate to the above solution to form a uniform white solution. In a vinyl-lined stainless steel autoclave, immerse the cleaned copper mesh in the above solution; under the condition of the autoclave closed, react at 100-150 °C for 24 hours, then cool to room temperature, take out the copper mesh, and wash with deionized water to obtain black nanosheets Stacked flower-like CuO. 2. an application method of electrocatalytic coupling advanced oxidation system as claimed in claim 1, it is characterized in that: in conventional H-type electrolytic cell reaction system, with three-dimensional hexagonal star-shaped Co ₃ O ₄ and nano-sheet stacking flower-shaped CuO was used as anode and cathode materials, respectively, adding 0.1 mol/L sodium sulfate solution to the anode compartment, adding 0.1 mol/L potassium bicarbonate solution to the cathode compartment, and then adding 0.5 g/L persulfate and 10 mg to the anolyte /L p-nitrophenol solution, electrified for electrolysis and advanced oxidation coupling reaction. 3. application method as claimed in claim 2 is characterized in that: the volume of the 0.1 mol/liter sodium sulfate solution that adds in anode compartment and the 0.1 mol/liter potassium bicarbonate solution that adds in cathode compartment is 60 milliliters. 4. the application of the electrocatalytic coupling advanced oxidation system as claimed in claim 1 in the field of sewage treatment, it is characterized in that: for removing organic pollutants in waste water, and described organic pollutants produce _CO at anode mineralization , introduced into the cathode through the exhaust pipe, and then reduced to hydrocarbons on the cathode.

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