Preparation Of Phosphotungstate Photocatalytic Materials And Performance Degradation Of Chlorothalonil

Polyoxometalates, as a kind of inorganic cluster compounds, have been widelyapplied in many fileds because of their unique structure and various properties, suchas industrial catalysis, materials science, pharmacy and so on. However, thetraditional heteropolyacid photocatalyst have some disadvantages such as strongsolubility in water, easily dissolution in water and oxygen-containing organic solvents,low efficiency of reuse, smaller specific surface area, difficult to be recycled, whichlimit the scope of heteropolyacid. However, if heteropolyacid were combined with thelarger radius of cation K+, NH4+to prepare heteropolyacid of non-water-soluble,heteropolyacid of non-water-soluble which prepared by heteropolyacid and the largerradius of cation K+, NH4+, not only can increase its corresponding specific surfacearea, make the product easy to separate, but also improve the repeatability andrecyclability in the application. Then heteropolyacid salt were loaded on mesoporoussilica, the photocatalytic activity of phosphotungstate salt can be improved due to itslarge specific surface area and smaller aperture of mesoporous silica. In this paper,We have done the following researches:1.The methods of determination chlorothalonil content in environmental waterhas been established by SPE-GC, the samples were enriched and purified by Florisilcolumn, eluted of3mL ethyl acetate, and analysed and deteced by GC-ECD. Theresults showed that the linear relationship of chlorothalonil pesticides residues waswell in0.01mg/L~10mg/L ranges, and it correlation coefficients was0.9993. Thedetection limit of quantitative method of external standard was in0.0035mg/L, andthe recoveries ranged from93.47%to100.14%, the relative standard deviations (n=6)were in the range of3.97%to10.83%. The method is simple, rapid, accurate and highsensitivity, and it satisfied the analysis requirements of pesticide residues inenvironmental water samples.2. With phosphotungstic acid, potassium chloride and ammonium chloride asraw materials，non-water soluble phosphotungstate photocatalysts of KPW1, KPW2,NH4PW1and NH4PW2were prepared by the dipping method and the refluxingmethod. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electronmicroscope(SEM), infrared radiation (IR), thermogravimetric analysis (TG)and ultraviolet-xisible spectroscopy (UV-Vis). Chlorothalonil was regard as a targetreactant, the degradation activity of four photocatalysts were investigated, and thedegradation mechanism was studied. The experimental results showed that KPW1have best degradation performance on chlorothalonil in the four kinds ofphotocatalysts, its degradation efficiency was more than80%on the condition of0.10g of KPW1,240min of light degradation time,5mg/L of chlorothalonil concentrationand pH value equal to5. The degradation rate of KPW2reached70%onchlorothalonil on the best conditions. While the degradation rate of NH4PW1andNH4PW2were less than70%on best conditions. It also suggested that the three kindsof photocatalysts of KPW2, NH4PW1and NH4PW2could be improved degradationefficiency on chlorothalonil. The characterization results showed that four kinds ofcatalyst particles were spherical shape, the particles are dispersed in an independentlyand dispersion was good, the introduction of K+and NH4+did not destroy the Kegginstructure of phosphotungstate, four kinds of catalyst has good light stability, whichcan be reused more than four times. The result of kinetics research showed that thefour photocatalyst degradation dynamics correspond with first order kineticsmodel,the study of GC-MS and IC showed that the degradation mechanism ofcatalysts on chlorothalonil was consistent.3.The mesoporous materials of KPW/SiO2and NH4PW/SiO2had been preparedby sol-gel method using TEOS, CTAB mixed with KPW2and NH4PW1under thealcohol-water system and alkaline conditions. KPW/SiO2and NH4PW/SiO2werecharacterizated by XRD, BET, IR and TG. The degradation properties of SiO2loadedon KPW2and NH4PW1were investigated, degradation process was studied at thesame time. The results showed that photocatalytic degradation of chlorothalonil hasbeen greatly improved. KPW/SiO2have better degradation performance onchlorothalonil, and the degradation rate increase to86.04%on the condition of0.01gof catalysts,120min of light degradation time,5mg/L of chlorothalonilconcentration and pH value equal to5.While the degradation rate of NH4PW/SiO2onchlorothalonilincreased to83.23%on the condition of0.02g of catalysts,180min oflight degradation time,5mg/L of chlorothalonil concentration and pH value equal to 5. The photocatalytic activity of phosphotungstate salt was improved by using silicatemplate to make of mesoporous materials.The dynamic behavior and degradationmechanism of KPW2and NH4PW1which loaded on mesoporous materials were samewith its before loaded on mesoporous materials.