Preparation Of TiO₂/CA Materials And Study On Photocatalytic Degradation Of PAHs In Soil Washing Eluents

PAHs are easy to be distributed from water into living organisms,in sedimentary layers,stable in soil and difficult to decompose and accumulate in the environment.Surfactant has obvious solubilization effect on PAHs in soil,which is the most promising leaching solution for PAHs contaminated soil.The PAHs solubilization wastewater produced by the contaminated soil after leaching with surfactant has chemical carcinogenicity,phototoxicity and mutagenicity,which is an urgent problem to be solved.In this paper,PAHs(naphthalene,phenanthrene)solubilization wastewater was studied,and three kinds of composite photocatalysts were prepared by physical method,chemical method and ZnC12 activation method.Density,XRD,polarized light electron microscopy,SEM,N2 adsorption-desorption curve,FT-IR and DRS were used to analyze the density,crystal shape,surface morphology,specific surface area,pore structure,functional group structure and optical properties of the composite photocatalyst.The solubilization properties of TX-100 pairs of naphthalene and phenanthrene were studied by solubilization experiment.The adsorption process of PAHs wastewater by composite photocatalyst was studied.Through photocatalytic degradation experiment,the photocatalytic degradation process and mechanism of TX-100 solubilized PAHs were studied by composite photocatalyst.The specific research contents are as follows:(1)TiO2-CA composite photocatalyst was prepared by physical method.It was composed of phenolic gel particles stacked in a uniform three-dimensional network structure.Its density was in the range of 200-500mg/cm3.It belongs to mesoporous materials.XRD shows that TiO2-CA is mainly based on anatase type TiO2.The specific surface area is controllable in the range of 500-600 m2·g-1,showing high adsorption performatce.The adsorption process of the TiO2-CA to PAHs solution solubilized by TX-100 of is accords with the Langmuir model and quasi-second-order rate equation,belonging to ?G<0,?H>0,?S>0 spontaneous adsorption behavior;The photocatalytic degradation process conforms to the pseudo-first-order kinetic equation.Under 25?,photocatalytic degradation process of 3g/L of TiO2(0.5)-CA(45)and TiO2(0.2)-CA(45)to 500 mg/L of naphthalene and 100 mg/L of phenanthrene solubilized by 5 g/L of TX-100 show the best effect.Dgradation rate of naphthalene and phenanthrene was 92.3%and 97.8%,respectively.Composite photocatalyst has selective adsorption and degradation effect on PAHs in solubilized wastewater.The photocatalytic degradation efficiency of TiO2(0.2)/CA(45)to PAHs is lower than that of TiO2(0.2)-CA(45).(2)The CA-TiO2-Zn series composite photocatalyst was prepared by ZnC12 activation method,with the minimum density controlled within 80mg/cm3.XRD shows that the CA-TiO2-Zn composite is a compound of ZnTiO3 and rutile TiO2(mainly ZnTiO3).The parameters such as the specific surface area of CA1-TiO2(0.1)-Zn(1215.92m2·g-1)and the total pore volume(0.692cm3·g-1)are the largest in the series of materials,showing the best adsorption performance.The adsorption process of the CA1-TiO2(0.1)-Zn to PAHs solution solubilized by TX-100 of is accords with the Langmuir model and quasi-second-order rate equation,belonging to ?G<0,?H>0,AS>0 spontaneous adsorption behavior;The photocatalytic degradation process conforms to the pseudo-first-order kinetic equation.