Preparation And Study Of The Photo-catalysis Performance Of The C-TiO₂/EGC Composite

Phenolic wastewater is a kind of most common and representative pollutants in our country.Adsorption based on expanded graphite-based composite is shown to be effective due to its large adsorption capacity and specific porous structure.This material not only enhances the flow of liquid,but also improves the efficiency of adsorption.However,the adsorption method of the composite has poor economic property.Moreover,discarding of the recycled material would cause environmental pollution and waste of resource.Thus,it is appealing to increase the adsorption capacity of the composite by introducing the photo-catalytic technique.In this work,expanded graphite-based composite(EGC) was prepared by impregnation of expanded graphite(EG) in H₃PO₄/sucrose solution followed by carbonization and activation.By then,TiO₂ was loaded on the exterior surface of EGC.The results indicated that the TiO₂/EGC had a high phenol removal rate because of its abundant mesoporous and microporous structure.With the parameters of 1.2 impregnation ratio,350℃activation temperature and 120min reaction time,the obtained TiO₂/EGC had the highest phenol removal rate.And also it showed that TiO₂ had the highest photo-catalytic activity as the mass ratio of anatase phase to rutile phase was 83/17.The results showed that the phenol removal efficiency reach 92.7%by EGC loaded by carbon coated TiO₂(C-TiO₂/EGC) at the TiO₂ loading amount of 11.57%, sucrose concentration of 0.5%and the heat treatment temperature of 750℃.As a binder,carbon film was used to support the TiO₂ on the surface of EGC substrate. Carbon film was beneficial to suppress the phase transformation,so TiO₂ could remains high photocatalytic activity property even calcinated at high temperature. Meanwhile,the carbon coated TiO₂ with suitable carbon doping has visible light response capacity.Factors affecting the photo-catalytic oxidation of phenol,such as initial viscosity, oxide amounts etc.were studied.When the phenol concentration was 50mg/L,the luminance was 7.75mw/cm²,pH was 7 and hydrogen peroxide concentration was 15 mL/L,the C-TiO₂/EGC has the highest phenol removal efficiency.The synergy effect between TiO₂ and EGC using C-TiO₂/EGC could be summarized as follows:(1) Phenol was adsorbed on the EGC and carbon layer coated with TiO₂.(2) Through the surface diffusing,phenol was migrated to the exterior loaded TiO₂ and the interior pores.(3) The phenol was oxidized by powerful oxidizing agents which were produced from carrying on photo-catalytic degradation.