Thermodynamics of removing crotamiton and its transformation byproducts from water by a rotating advanced oxidation contactor with zeolite/TiO2 composite sheets

Abstract

A rotating advanced oxidation contactor (RAOC) equipped with zeolite/TiO2 composite sheets was used to evaluate the thermodynamics of removing crotamiton (CTM) and its transformation byproducts from water. The effect of solution temperature (283–313 K) on CTM adsorption rate by the zeolite, CTM degradation rate by the TiO2, and CTM degradation rate by the zeolite/TiO2 composite was evaluated separately, and enhancement of the synergetic effect on CTM degradation by temperature increase was discussed. The maximum adsorption capacity for CTM was stable at a given temperature, whereas the Langmuir constant increased with the increase in temperature. The increase in temperature enhanced the rate for both adsorption and degradation of CTM, and CTM degradation was more affected by temperature than CTM adsorption. Removing CTM through both adsorption and degradation proceeded more rapidly than through degradation alone because the increase in temperature enhanced the synergetic effect on CTM degradation. The activation energies were estimated to be 30.4 kJ/mol for CTM adsorption, 48.7 kJ/mol for CTM degradation, and 44.9 kJ/mol for removing CTM through both adsorption and degradation. The transformation byproduct P219, produced via hydroxylation of the aromatic ring of CTM, was detected during photocatalysis of CTM, and its behavior was explored. As with CTM, the production and removal of P219 proceeded rapidly with an increase in the solution temperature. These results show that solution temperature is an important factor that affects the performance of the RAOC treatment.