Preparation Of MoS₂ Composites And Application In Treatment Of Organic Pollutant In Wastewater

Phenols and dye are the main pollutants in wastewater.Most phenols compounds have the characteristics of high content and high toxicity,indicating that light has a great impact on degradation.According to the characteristics of phenolic and dyeing wastewater,it is difficult to remove organic pollutants from wastewater completely.In this work,the combination of photocatalysis and Fenton oxidation can improve the degradation efficiency of organic pollutants in wastewater.The method for removal of organic pollutants is safe,simple and efficient,and also has no secondary pollution to the environment.The MoS₂ and MoS₂ composites were parepared and used to remove several types of pollutants including phenol?catechol?methylene blue?methyl orange and rhodamine B in waster water.The main results are as follows:Different morphology of MoS₂ have been successfully synthesized through a facile one-pot solvothermal method.The effects of reaction temperature?material ratio and different stabilizers on the structural and properties of MoS₂ were optimized.MoS₂ catalysts were characterized by means of XRD?SEM and XPS,etc.The results show that the morphology of the lamellar structure of the MoS₂,which is composed of many nanosheets stacked and intertwined and uniform particle size distribution.The photocatalytic degradation of phenol,phenol over visible light MoS₂ and H₂O₂ was investigated in aqueous solution.The effects of various experimental parameters such as pH?catalyst concentrationphenol concentration and reaction temperature on the catalytic degradation of phenol were studied.Optimum conditions such as pH = 8.0,[catalyst]= 1.5 g·L-1 and T = 40?,respectively,were obtained.The degradation rate of 98.7%and COD Removal rate of 65%were observed under the optimum conditions,which indicated that MoS₂ had good catalytic activity.The degradation kinetics of catechol follows pseudo first-order kinetics.Under visible light and in the presence of H₂O₂,The degradation rate of the catalyst was 0.0612 min-1 under the presence of UV and H₂O₂,which is about 3.26 times higher than that of using pure H₂O₂ as the Fenton catalyst.At the same time,MoS₂ catalyst showed good stability in the degradation process.Fe₃O₄@MOS2 core-shell composites were prepared by in situ growth of MoS₂ nanosheets on the surfaces of Fe₃O₄ nanoparticles under different temperature.The Fe₃O₄@MOS2 samples were characterized by SEM?TEM?XRD?BET and VSM.The results show that the MoS₂ nanosheets are loaded on the surface of Fe₃O₄ particles at a reaction temperature of 180? and the specific surface area is 75.2 m²/g.The saturation magnetic strength value is smaller than that of Fe₃O₄.Using catechol as the target,the results show that the degradation rate and COD removal rate can reach 99.0%and 90.0%,respectively in the following initial conditions:[H₂O₂]= 10 mmol.L-1,[catalyst]=1.0 g·L-1,,[catechol]= 50 mg/L,pH = 7.2.The degradation kinetics of catechol follows pseudo first-order kinetics.In the presence of both light and H₂O₂,the degradation rate is much faster than that of H₂O₂ alone and light,The catalytic reaction rate is 2 times of its photocatalytic and Fenton oxidation rate,which indicates that Fe₃O₄ and MoS₂ have synergistic effect in the process of degradation.For the simulated catechol wastewater,the catalyst cycling has little effect on the catalytic activity,after four cycling,the catalytic activity was reduced by only 5%,The results show that Fe₃O₄@MoS₂ core-shell composites have better stability in the process of degradation.Adsorption of MB is a spontaneous degree of spontaneous increase in the endothermic process.MoS₂@C core-shell composites were prepared by high temperature in-situ carbonation.The MoS₂@C samples were characterized by scanning electron microscopy,X-ray diffraction,specific surface area and Raman analysis.The results show that the carbon nanosheets are uniformly coated on the surface of the MoS₂ nanosheetand the specific surface area is 586 m²/g.Adsorption of MB by MoS₂@C absorbent was investigated in a batch system.MoS₂@C core-shell composites have higher removal rate that of MoS₂ alone,The results showed that the removal rate of methylene blue was 99.7%when the adsorption temperature was 45?,the pH value was near neutral and the adsorbent concentration was 1.75 g/L.The correlation coefficient R2>0.999 of the second-order kinetic model is better than that of the first-order kinetic model.The kinetic experiment data of MoS₂@C composites are well described.Dubinin-Radushkevch,Temkin and Langmuir model fitted the data well.The adsorption capacity of Langmuir monolayer reached 276.4 mg/L.According to the Dubinin-Radushkevch model,the mean free energy of adsorption of methylene blue was 3.53 kJ/mol.The adsorption of MB onto MoS₂@C was mainly attributed to the physical adsorption.Thermodynamic parameters for the adsorption system were determinated at different initial concentrations and different temperatures,?G ?-12.77-1.77 kJ/mol,?H= 1.24-6.81 kJ/mol,?S=9.55-46.71 kJ/?mol.K?.Adsorption of MB is a spontaneous degree of spontaneous increase in the endothermic process.The adsorption of MB mechanism may be attributed to the the hydrogen bond force and dipole gravitational interaction between adsorbent surface,water molecules and MB molecules.