Continuous Treatment Of Phenolic Effluent By Heterogeneous Catalyts In A Fixed-bed Reactor

Fe2O3/?-Al2O3 catalysts were prepared by wet impregnation method and were characterized by X-ray Diffraction(XRD),Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),nitrogen adsorption(BET)and temperature programmed desorption of ammonia(NH3-TPD).Effects of several factors,such as the space time,the reaction temperature,the concentration of H2O2 and the initial pH,have been studied in order to optimize the operation conditions.The results shown that it was efficient to degrade the phenol of 1000 mg/L under the space time was 41.7 gcat·h/gPnOH,the reaction temperature was 80?,the concentration of H2O2 is 5.1 g/L(1.0 Qth),the particle size was 0.9-1.5 mm and the initial pH=4.5(not adjusted).The phenol removal is almost complete and COD removal is about 92%at steady-state(in 10 min)conditions under the best operation conditions.Meanwhile,the intermediate products were determined by HPLC.The results showed that there were four kinds of intermediate products,catechol,hydroquinone,resorcinol and p-benzoquinone,respectly.The intermediate products were oxidized to quinones firstly,then further degraded into tartaric acid,oxalic acid,acetic acid and formic acid,and finally were degraded into CO2 and H2O.In the modified Fe2O3/?-Al2O3 catalysts using a small amount of rare elements by the characterizations and activity evaluation,CuO-Fe2O3/?-Al2O3 catalyst was better than others with completely phenol removal and 97%COD removal under the best operation conditions.In addition,the stability of the Fe2O3/?-Al2O3 and CuO-Fe2O3/?-Al2O3 were studied,The catalysts were used in continuous operation up to 64 h and the activitis decrease of the two catalysts are not obvious,Fe2O3/?-Al2O3 on phenol removal rate from 100%to 91%,COD removal rate can reach 72%,CuO-Fe2O3/?-Al2O3 catalyst removal of phenol from 100%to 95%,COD removal rate can be reached about 75%.The stability of the CuO-Fe2O3/?-Al2O3 is better than Fe2O3/?-Al2O3.And the partial deactivation of the catalyst is mainly due to complexation of active sites with acid organic compounds and adsorption of intermediate products.The deposition of organic carbon and the leaching of iron have a little role to the partial deactivation of the catalyst.The leaching Fe ions from the catalyst has part contribution to phenol degradation at short-term run,then this contribution could be neglected after long-term operation due to the amount of leaching Fe ions decreased to be negligible.The partial deactivated catalysts can be regenerated through simple treatment method.