Study On Tcb Removal From Water Using Microwaved MWNTs/TiO₂Composite

This study investigated the photodegradation of1,2,3-trichlorobenzene usingmicrowave-induced MWNTs/TiO₂and the composite photocatalysts prepared bymicrowave modified MWNTs. The effects of photocatalytic activity with differentmodification had been studied, the respective modification conditions of compositephotocatalysts with the highest photocatalytic activity were selected, then had beenused in the photodegradation of trichlorobenzene.Composite photocatalyst, MWNTs/TiO₂, was prepared using sol-gel method anddried through microwave irradiation. Characterization of the composite showed that,with increase of microwave power until400W, the average diameter of TiO₂crystalcoated MWNTs reduced gradually, and better dispersion of the composites was alsoacquired at this microwave power400W. However, further increase of the powerresulted in the average diameter of the MWNTs enlarged, and more aggregativecomposites were obtained. Furthermore, photodegradation of1,2,3-trichlorobenzene（1,2,3-TCB） with the microwave-induced composite photocatalysts of MWNTs/TiO₂,was studied. It is founded that the photodegradation of1,2,3-trichlorobenzenefollowed first-order kinetics. The microwaving conditions for producing thecomposite photocatalysts with highest photocatalytic activity were further determinedas5min irradiation at400W. Under such conditions, the photodegradation rateconstant of1,2,3-trichlorobenzene was0.0237min-1which was elevated by52%comparing to those obtained using non-microwaved composites.Using microwave irradiation to modify MWNTs under N2atmosphere or not,then prepared composite photocatalysts MWNTs/TiO₂, and investigated the effect ofphotocatalytic degradation of1,2,3-trichlorobenzene to determine the effectivemodification method in this paper. The results showed that the photocatalytic activityof composite photocatalysts would be better with the MWNTs modified in N2atmosphere, and microwaved MWNTs without N2was damaged severely, thusMWNTs microwave-induced under N2atmosphere was selected for further study.Using1,2,3-trichlorobenzene as the pollutant and according to the difference ofphotocatalytic activities among the composite photocatalysts under differentmodifying conditions the best modifying condition method was selected, which wasmicrowave power of400W for8min, and nitrogen flow of0.4L/min. Qualitative analysis by FTIR, it showed that the functional groups of the MWNTs before andafter modification mainly existed on the surface were hydroxyl （-OH）, double bonds（-C=C）, carboxyl （-COOH）, etc, and the surface of modified MWNTs arouse alkalinegroups amine （N-H）. The results of Boehm showed that after microwave treatment,the acidic groups and carboxyl of MWNTs decreased and the alkaline functionalgroups increased.Using composite photocatalysts prepared under optimal conditions of the twomodification methods respectively to degradation three typical chlorobenzenes. It wasfound that, the degradation efficiency and rate of composite photocatalysts aftermodification were increased, and the order of photocatalytic degradation rateconstants were:1,2,3-trichlorobenzene>1,2,4-trichlorobenzene>1,3,5-trichloroben-zene. The degradation rate of microwave-induced MWNTs/TiO₂and the compositephotocatalysts prepared by microwave modified MWNTs increased by52⁶5%and78⁸4%respectively.In summary, the photocatalytic activities of microwave-induced MWNTs/TiO₂and the composite photocatalysts prepared by microwave modified MWNTs weregreatly improved compared to the traditional composite photocatalysts, and wouldhave potential applications in water treatment of chlorobenzene organic pollutants.