The Study On The Combined Treatment Of Coking Wastewater By The Modificated Char And Metal-doped TiO₂

In this paper,The different varieties of doping modified nanometer TiO₂ photocatalyst were prepared by sol-gel hydrothermal synthesis.At the same time,TiO₂ and biomass-modified char was prepared.The photocatalytic activity of different photocatalyst and the adsorption behavior were tested with simulated phenol wastewater as the treatment of target.Preparation conditions of photocatalyst,experiment conditions,reaction conditions,reaction kinetics and reaction mechanisms were studied and the biodegradability of treated wastewater was also discussed.The experimental results show that Ce（NO3）3（1%）and hexamethylenetetramine（14%）as the metal and nitrogen source,the photocatalytic degredation efficiency of Ce,N-TiO₂ catalysts（T（hydrothermal）=160 ℃,T（calcination）=200 ℃,t（hydrothermal）=24h,t（calcination）=3h,pH=2）can reach up to 69%.O3 was chosen as the auxiliary oxidant,O3/Ce,N-TiO₂ increased the the photocatalytic efficiency up to 80%.The results of modified char research showed that the best coal resource was Shanxi bituminous coal,modified method was biomass（Hainan coconut shell,30%）and TiO₂（1%）modification.The optimum concentration was 600 mg / L,dosage of char is 4g / L,and the concentration of phenol can be removed to 150 mg/L or less.Compared with the separated,the results of combination of modified char adsorption and photocatalysis greatly improved the biodegradability and efficiency of the phenol wastewater.The photocatalysts and char were characterized and analysed through the method of XRD,NH3-TPD,BET and UV-vis DRS.We found that the specific surface area of coal chars modified by biomass increased.Ce and N doping reduced the crystallinity of the Ce,N-TiO₂,the band gap of the particles is reduced,and the red-shift of the catalyst is extended to broaden the range of visible light response and the visible-light catalytic performance improved.In addition,the surface acidity of the catalyst were improved,which further enhanced the adsorption performance,and was also one of the reasons for the improvement of the photocatalytic performance of the modified TiO₂ catalyst.The results were consistent with the experimental data.The results of photocatalytic degradation products showed that phenol is decomposed into small molecules in the first step,and then the small molecules are completely oxidized in the next step.The kinetic study shows that the adsorption of modified coal charcoal and the photocatalytic reaction of TiO₂ conformed first-order kinetics.