Method for degrading dimethyl sulfoxide wastewater by ultrasonic wave and photocatalytic reaction

Abstract

The invention discloses a method for degrading dimethyl sulfoxide wastewater through ultrasonic wave and photocatalytic reaction. According to the method, urea and P25 are taken as raw materials, a P25 / g-C3N4 composite catalyst is synthesized by adopting a mixed calcination method, and then DMSO is degraded by using the P25 / g-C3N4 composite catalyst under ultrasonic synergism. Through the synergistic effect of ultrasonic waves, a large number of hydroxyl radicals can be generated, the catalyst is promoted to be evenly distributed, DMSO in the solution is further subjected to oxidative degradation, the pH of wastewater does not need to be adjusted, and the highest removal rate of dimethyl sulfoxide can reach 100%.

Description

Technical Field

[0001] The invention belongs to the field of advanced oxidation treatment of organic wastewater and relates to a method for degrading dimethyl sulfoxide wastewater by using ultrasound-assisted photocatalytic reaction. Background Art

[0002] Dimethyl sulfoxide (DMSO) is a polar molecule with high solubility for ionic and polar substances, earning it the nickname "universal solvent." DMSO has a high boiling point and excellent stability at high temperatures. It is miscible with water and is compatible with most organic solvents and polar gases. Therefore, it can be used as a reaction medium solvent for dyes, pharmaceuticals, and semiconductor electroplating, as well as a transdermal enhancer and analgesic in the pharmaceutical field. However, DMSO-containing wastewater from industrial production is difficult to fully recycle, and direct biological treatment can easily produce toxic substances such as hydrogen sulfide and sulfides. These intermediates can cause secondary pollution to the ecological environment.

[0003] Photocatalytic advanced oxidation (PAO) is an advanced oxidation technology that has evolved based on the basic principles of photochemical oxidation. This technology uses fixed-wavelength light to irradiate a photocatalyst, generating highly active free radicals that effectively degrade organic matter in water. A photocatalyst is a material that catalyzes degradation reactions under light excitation. Semiconductor catalysts have been the focus of much research, with currently garnering significant attention among the catalytic materials: titanium dioxide (P25), bismuth photocatalysts (BiOBr, BiOI, BiOCl), graphitic carbon nitride (g-C3N4), and bismuth tungstate (Bi2WO6). While PAO offers advantages such as mild reaction conditions, high catalytic efficiency, and the ability to harmlessly treat organic matter, its development has been hampered by issues such as incomplete reactions when the solution has low light transmittance and the susceptibility of electron-hole recombination in the catalyst. Summary of the Invention

[0004] The present invention aims to provide a method for degrading dimethyl sulfoxide (DMSO) wastewater using an ultrasound-assisted photocatalytic reaction. This method uses urea and P25 as raw materials, calcining to synthesize a P25 / g-C3N4 composite catalyst. The P25 / g-C3N4 composite catalyst is then used to degrade DMSO solution under ultrasound. The method exhibits advantages such as high DMSO removal efficiency and the absence of pH adjustment.

[0005] The technical solutions for achieving the purpose of the present invention are as follows:

[0006] The method for degrading dimethyl sulfoxide wastewater by ultrasound-assisted photocatalytic reaction comprises the following steps:

[0007] (1) Urea and P25 were mixed in a mass ratio of 2 to 10:1 and calcined in a muffle furnace at 350 to 650°C for 1 to 3 hours. After cooling to room temperature, the sample was washed with water, dried, and ground to obtain a P25 / g-C3N4 composite catalyst;

[0008] (2) P25 / g-C3N4 composite catalyst was added to the DMSO solution, and ultrasonication was performed in the dark until the catalyst was evenly dispersed. Then, light was applied and ultrasonication was continued to catalytically degrade DMSO.

[0009] Preferably, in step (1), the heating rate is 3-5°C / min and the calcination temperature is 500°C.

[0010] Preferably, in step (2), the ultrasonic power is 40-80 W, the ultrasonic frequency is 25-75 KHz, and the ultrasonic temperature is 40-80° C.

[0011] Preferably, in step (2), the light source is a 35W xenon lamp.

[0012] Preferably, in step (2), ultrasound is performed in the dark for more than 1 hour, and then the ultrasound is continued under light for more than 3 hours.

[0013] Preferably, in step (2), the mass ratio of the P25 / g-C3N4 composite catalyst to DMSO is 4 to 8:1.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The present invention combines g-C3N4 with P25 to form a P25 / g-C3N4 composite catalyst. This increases the separation efficiency of electron-hole pairs and improves the photocatalytic performance of the material. Furthermore, the band gap of the material is narrowed, expanding the spectral absorption range of the material. Furthermore, under the action of ultrasound, a negative pressure zone is generated within the solution, leading to the formation of cavitation bubbles (cavities). When these bubbles burst, instantaneous high temperature and high pressure are generated. Consequently, a large amount of hydroxyl radicals can be generated in the reaction system, further oxidizing and degrading DMSO in the solution. When the method of the present invention is used, there is no need to adjust the pH value of the wastewater, and the dimethyl sulfoxide removal rate is high, reaching up to 100%. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to specific embodiments.

[0017] Example 1

[0018] (1) 10 g of urea and 5 g of P25 were placed in a muffle furnace and heated to 500 °C at a heating rate of 3 °C / min and calcined for 3 h. After the temperature in the muffle furnace cooled to room temperature, the prepared sample was taken out and washed with deionized water to remove impurities adsorbed on the sample. Finally, the sample was dried and ground to obtain a P25 / g-C3N4 composite catalyst.

[0019] (2) Prepare a glass reactor, fill it with 100 mL of a 100 mg / L DMSO solution, add 40 mg of a P25 / g-C3N4 composite catalyst, and place it in an ultrasonic cleaner with a power of 40 W, a frequency of 25 kHz, and a temperature of 40°C for catalytic reaction. The liquid level in the glass reactor should be lower than the liquid level in the ultrasonic cleaner. First, conduct an adsorption test in darkness for one hour, then illuminate it for three hours under a 35 W xenon lamp. During the illumination period, sample the culture dish every half hour, centrifuge, and collect the supernatant. The absorbance of the DMSO solution after photocatalysis is measured using a UV-2300 UV-visible spectrophotometer. The removal rate of dimethyl sulfoxide was measured to be 91%.

[0020] Example 2

[0021] This embodiment is substantially the same as embodiment 1, except that 80 mg of P25 / g-C3N4 catalyst is added in step (2). The final removal rate of dimethyl sulfoxide is measured to be 97%.

[0022] Example 3

[0023] This embodiment is basically the same as embodiment 2, except that the ultrasonic frequency in step (4) is 75 KHz, and the removal rate of dimethyl sulfoxide is measured to be 100%.

[0024] Comparative Example 1

[0025] This comparative example is substantially the same as Example 1, except that 40 mg of P25 is used as the catalyst. The removal rate of dimethyl sulfoxide is measured to be 32%.

[0026] Comparative Example 2

[0027] (1) 10 g of urea was placed in a muffle furnace and heated to 500 °C at a heating rate of 3 °C / min and calcined for 3 h. After the temperature in the muffle furnace cooled to room temperature, the prepared sample was taken out and washed with deionized water to remove impurities adsorbed on the sample. Finally, it was dried and ground to obtain the g-C3N4 catalyst.

[0028] (2) The method is substantially the same as Example 1, except that 40 mg of g-C3N4 is added, and the removal rate of dimethyl sulfoxide is measured to be 58%.

[0029] Comparative Example 3

[0030] This comparative example is substantially the same as Example 3, except that ultrasound was not used in step (2). The removal rate of dimethyl sulfoxide was measured to be 87%.

Claims

1. A method for degrading dimethyl sulfoxide wastewater by ultrasonic-assisted photocatalytic reaction, characterized in that: The following steps are involved: (1) Urea and P25 were mixed in a mass ratio of 2-10:1 and calcined in a muffle furnace at 350-650°C for 1-3 h. After cooling to room temperature, the sample was washed with water, dried, and ground to obtain a P25 / g-C3N4 composite catalyst. (2) P25 / g-C3N4 composite catalyst was added to the DMSO solution, and ultrasonication was performed in the dark until the catalyst was evenly dispersed. Then, light was applied and ultrasonication was continued to catalytically degrade DMSO.

2. The method according to claim 1, characterized in that In step (1), the heating rate is 3-5°C / min and the calcination temperature is 500°C.

3. The method according to claim 1, characterized in that In step (2), the ultrasonic power is 40-80 W, the ultrasonic frequency is 25-75 kHz, and the ultrasonic temperature is 40-80° C.

4. The method according to claim 1, wherein In step (2), the light source is a 35W xenon lamp.

5. The method according to claim 1, wherein In step (2), ultrasonication is performed for more than 1 hour in dark conditions, and then the cells are exposed to light and ultrasonication is continued for more than 3 hours.

6. The method according to claim 1, characterized in that In step (2), the mass ratio of the P25 / g-C3N4 composite catalyst to DMSO is 4~8:1.