Preparation of a photoelectrocatalytic membrane and method for applying the same to degradation of antibiotic wastewater

Abstract

The application discloses a preparation method of a photoelectrocatalytic membrane and application of the photoelectrocatalytic membrane to antibiotic wastewater degradation, and comprises the following steps: (1) preparing ultrathin g-C3N4 nanosheets by using dicyandiamide and melamine; (2) preparing a g-C3N4 / BiVO4 heterojunction by using a hydrothermal method; (3) preparing a photoelectrocatalytic membrane by using a non-solvent induced phase separation method; (4) taking a CB / C / PVDF membrane (2*3 cm 2 ) as an anode, a platinum sheet electrode as a cathode, and 0.05M Na2SO4 as an electrolyte solution to form a PEC system; and (5) applying a 1.0V voltage, adjusting pH=3, and degrading tetracycline hydrochloride at a degradation rate of 93.6% within 3h, wherein the catalytic membrane can be recycled and can be efficiently operated at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of membrane material technology, specifically relating to the preparation of a photoelectrocatalytic membrane and its application in the degradation of antibiotic wastewater. Background Technology

[0002] With the continuous development of industrialization and urbanization, antibiotics that are difficult to degrade in water bodies have led to increasingly serious water pollution problems, posing a serious threat to the balance of ecosystems and human health. Therefore, the efficient removal of antibiotics from wastewater has attracted widespread attention.

[0003] Photocatalytic membrane technology, by immobilizing photocatalysts on the membrane surface or embedding them into the pore structure of the substrate membrane, can efficiently degrade pollutants in water and on the membrane surface under visible light irradiation, effectively preventing membrane fouling and gradually becoming an attractive technology in wastewater treatment. On one hand, pollutants in the water are degraded by the catalyst, while pollutants on the membrane surface can also be oxidized, thus achieving a self-cleaning process for the membrane. On the other hand, the catalyst integrated with the membrane can be easily recovered and reused, effectively solving the energy consumption problem in the photocatalyst recovery process.

[0004] Photocatalytic membranes still face problems that need to be solved, such as catalyst deactivation on the membrane, reduced membrane permeability, and more seriously, insufficient reaction kinetics, which reduces reaction efficiency.

[0005] Photoelectrocatalysis can effectively compensate for the shortcomings of photocatalytic membranes. Its main advantages are: (1) The photogenerated electron-hole pairs generated by the photoelectrode can move to another electrode through an external circuit, which can realize the rapid transmission of electrons; (2) The pore structure of the membrane provides more catalytic active sites, ensuring a high photoelectric conversion efficiency; (3) The system does not produce secondary pollution and can be reused; (4) By applying a positive bias voltage to the photoanode or a negative bias voltage to the photocathode, the separation of photogenerated charges can be further promoted, thereby improving the catalytic reaction performance of the photoelectrochemical system.

[0006] Therefore, based on the above research and analysis, this paper proposes to use photoelectrocatalytic membranes to degrade antibiotic wastewater while mitigating membrane fouling. Summary of the Invention

[0007] The purpose of this invention is to construct a photoelectrocatalytic system using an electro-assisted photocatalytic membrane, thereby enhancing the reaction kinetics of the photocatalytic membrane and efficiently degrading antibiotics in water. The technical solution of this invention is summarized below:

[0008] (1) Preparation of ultrathin g-C3N4 nanosheets. 3g of dicyandiamide and 15g of ammonium chloride were added to 10mL of deionized water and then dried at 80℃. Subsequently, the final solid precipitate was heated to 550℃ at a heating rate of 2℃ / min and calcined for 4 hours. After cooling to room temperature, the product was washed and dried at 60℃ for 24h, and then ground into powder.

[0009] (2) Preparation of g-C3N4 / BiVO4 heterojunctions: Bi(NO3)3·5H2O was dissolved in HNO3 solution, denoted as solution A. Simultaneously, NH4VO3 was dissolved in NaOH solution (2M), denoted as solution B. Solution B was then added to solution A, and the resulting suspension was sonicated at room temperature. g-C3N4 was then added, and the mixture was stirred continuously for 1 h. The suspension was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and heated at 180 °C for 12 h. After natural cooling, the mixture was repeatedly washed with distilled water and alcohol. Finally, it was dried at 80 °C to obtain BiVO4 / g-C3N4 nanoparticles.

[0010] (3) Pretreatment of PVDF membrane. In order to improve the hydrophilicity of carbon cloth, the hydrophilic carbon cloth was boiled with hydrochloric acid (0.1%) for at least 30 minutes, then washed with deionized water 5 times, and dried at 50°C for 2 hours to remove impurities and improve conductivity.

[0011] (4) Preparation of photoelectrocatalytic membrane (CB / C / PVDF membrane). A solvent-inducible phase separation method was used to prepare the CB / C / PVDF membrane. A certain amount of catalyst and N-methylpyrrolidone (NMP) were ultrasonicated for 30 min. Subsequently, PVDF and superconducting carbon black were added to the dispersion, stirred at room temperature for 6 h, and allowed to stand to remove bubbles, resulting in a membrane casting solution containing PVDF. Next, the prepared membrane casting solution was coated onto one side of a carbon cloth using a coating applicator. After evaporation in air for 15 s, the membrane was immediately immersed in deionized water for 24 h to leach out residual solvent, and then stored in deionized water until use. The mass fractions of catalyst added were 1%, 3%, and 5% of the total mass, respectively. The preparation process of the catalyst-free C / PVDF membrane was the same as above, except that no catalyst was added.

[0012] (5) Photoelectrocatalytic degradation of tetracycline hydrochloride. The photoelectrocatalytic degradation process was carried out in a quartz electrochemical reactor. 100 mL of a 10 mg / L tetracycline hydrochloride solution was added to the reactor, and a CB / C / PVDF membrane (2 × 3 cm⁻¹) was used. 2 The PEC system consisted of a platinum sheet electrode as the anode, a platinum sheet electrode as the cathode, and 0.05M Na₂SO₄ as the electrolyte solution. The experiment used a DC regulated power supply with a forward bias of 0-1.3V and a 300W xenon lamp with a cutoff filter (λ > 420nm) as the light source. Stirring was employed during the experiment, and 0.1 mol / L... -1The initial pH of the reaction system was adjusted to 3 using H2SO4 solution. The reactor was placed 15 cm away from the light source, and 1 mL samples were taken at fixed time intervals. The absorbance at 357 nm was analyzed using a UV-Vis spectrophotometer to determine the change in tetracycline hydrochloride concentration.

[0013] Advantages of this invention:

[0014] 1. The membrane prepared by this invention has good electrical conductivity, chemical stability, and no secondary pollution;

[0015] 2. The membrane prepared by this invention has a high degradation rate and can be recycled. Attached Figure Description

[0016] Figure 1 This is a graph showing the degradation efficiency of tetracycline hydrochloride in different systems;

[0017] Figure 2 This is a graph showing the degradation efficiency of tetracycline hydrochloride under different bias voltages. Detailed Implementation

[0018] The present invention will be further described below through specific embodiments.

[0019] The following examples are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way.

[0020] The present invention will be described in detail below with reference to specific embodiments.

[0021] The following examples are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way.

[0022] The specific steps for preparing the photoelectrocatalytic membrane in Example 1 are as follows:

[0023] (1) Add 3g of dicyandiamide and 15g of ammonium chloride to 10mL of deionized water and dry at 80℃. The resulting solid precipitate is heated to 550℃ at a heating rate of 2℃ / min and calcined for 4h. After cooling to room temperature, the product is washed and dried at 60℃ for 24h, and then ground into powder.

[0024] (2) Dissolve 2.425g Bi(NO3)3·5H2O in 20mL HNO3 solution (2M), denoted as solution A. Simultaneously, dissolve 0.585g NH4VO3 in 10mL NaOH solution (2M), denoted as solution B. Then, add solution B to solution A and sonicate the resulting suspension at room temperature for 30min. Next, add 0.1g UCN to the above yellow suspension (pH=7) and stir continuously for 1h.

[0025] (3) The above suspension was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and heated at 180 °C for 12 h. After natural cooling, the obtained yellow powder sample was repeatedly washed with distilled water and alcohol. Finally, after drying at 80 °C, BiVO4 / g-C3N4 nanoparticles were obtained.

[0026] (4) In order to improve the hydrophilicity of the carbon cloth, the hydrophilic carbon cloth was boiled with hydrochloric acid (0.1%) for at least 30 minutes, then washed with deionized water 5 times, and dried at 50°C for 2 hours to remove impurities and improve conductivity.

[0027] (5) A CB / C / PVDF membrane was prepared by a solvent-inducible phase separation method. 0.16 g of BiVO4 / g-C3N4 and 7.36 g of NMP were sonicated for 30 min. Subsequently, 0.64 g of PVDF and 0.19 g of superconducting carbon black (30% of the weight of the PVDF membrane) were added to the dispersion, stirred at room temperature for 6 h, and allowed to stand to remove bubbles, thus obtaining a membrane casting solution containing PVDF.

[0028] (6) The prepared membrane casting solution was coated onto one side of the carbon cloth using a coating applicator. The thickness of the PVDF membrane was 400 μm. After evaporating in the air for 15 s, the membrane was immediately immersed in deionized water for 24 h to leach out the residual solvent. Then it was stored in deionized water until use.

[0029] Example 2: Experiment on the degradation of tetracycline hydrochloride by photo-Fenton membrane

[0030] With a surface area of ​​2×3cm 2 A CB / C / PVDF membrane was used as the anode and a platinum sheet electrode as the cathode, with 0.05M Na₂SO₄ as the electrolyte solution to form the PEC system. The experiment was conducted using a DC regulated power supply to provide bias and a 300W xenon lamp with a cutoff filter (λ > 420nm) as the light source. Stirring was employed during the experiment, and 0.1 mol L⁻¹ of [electrolyte name missing] was used. -1 The initial pH of the reaction system was adjusted to 3 using H2SO4 solution. The reactor was placed 15 cm away from the light source, and 1 mL samples were taken at fixed time intervals. The absorbance at 357 hm was analyzed using a UV-Vis spectrophotometer to determine the change in tetracycline hydrochloride concentration.

Claims

1. A method for degrading antibiotic wastewater using a photoelectrocatalytic membrane, characterized in that... Antibiotic wastewater was degraded using a CB / C / PVDF photoelectrocatalytic membrane in a quartz electrochemical reactor. The antibiotic to be degraded was tetracycline hydrochloride at a concentration of 10 mg / L. A PEC system was constructed using the CB / C / PVDF photoelectrocatalytic membrane as the anode, a platinum electrode as the cathode, and Na2SO4 as the electrolyte solution. A DC regulated power supply provided the bias voltage, and a 300W xenon lamp with a cutoff filter (λ > 420 nm) provided the light source. The experiment was conducted under stirring conditions. The initial pH of the reaction system was adjusted to 3, and 1 mL samples were taken at fixed time intervals. The absorbance at 357 nm was analyzed using a UV-Vis spectrophotometer, and the change in tetracycline hydrochloride concentration was measured. The preparation method of the CB / C / PVDF photoelectrocatalytic membrane included the following steps: Step S1, preparing ultrathin g-C3N4 nanosheets: dicyandiamide and ammonium chloride were added to 10 mL of deionized water and dried at 80 °C. The resulting solid precipitate was calcined in a muffle furnace and cooled. After reaching room temperature, wash, dry, and grind into powder; Step S2, prepare g-C3N4 / BiVO4 heterojunction: dissolve Bi(NO3)3·5H2O in 20mL nitric acid solution to obtain solution A, dissolve NH4VO3 in 10mL 2mol / L sodium hydroxide solution to obtain solution B, mix solution A and solution B and sonicate, add g-C3N4 and stir continuously, so that the resulting suspension is used to prepare g-C3N4 / BiVO4 heterojunction by hydrothermal method; Step S3. To prepare a CB / C / PVDF photocatalytic membrane, hydrophilic carbon cloth was boiled, washed, and dried with 0.1% hydrochloric acid. A non-solvent-induced phase separation method was used to ultrasonically disperse g-C3N4 / BiVO4 heterojunction and 92wt% N-methylpyrrolidone. PVDF and superconducting carbon black were then added to the dispersion. The mixture was stirred at room temperature and allowed to stand to remove bubbles. The resulting membrane casting solution was coated onto one side of the carbon cloth using a coating applicator. The membrane was then immersed in deionized water for 24 hours to obtain the CB / C / PVDF photocatalytic membrane.

2. The method according to claim 1, wherein, In step S1, the mass ratio of dicyandiamide to ammonium chloride is 1:

5.

3. The method according to claim 1, wherein, In step S2, the mass fraction of g-C3N4 in the g-C3N4 / BiVO4 heterojunction is 10%.

4. The method according to claim 1, wherein, In step S2, the reaction conditions for the mixed solution in the reactor are heating at 180°C for 12 hours.

5. The method according to claim 1, wherein, In step S3, the loading amount of the g-C3N4 / BiVO4 heterojunction is 1%-5% based on the total mass of the film casting solution, and the amount of superconducting carbon black added is 30% based on the mass of PVDF.

6. The method according to claim 1, wherein, The bias voltage range is 0-1.3V.

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