Degradation of high concentration 2,4-dichlorophenol by simultaneous photocatalytic-enzymatic process using TiO ₂/UV and laccase

Removal of 2,4-dichlorophenol (2,4-DCP) by TiO ₂/UV photocatalytic, laccase, and simultaneous photocatalytic-enzymatic treatments were investigated. Coupling of native laccase with TiO ₂/UV showed a negative synergetic effect due to the rapid inactivation of laccase. Immobilizing laccase covalently to controlled porous glass (CPG) effectively enhanced the stability of laccase against TiO ₂/UV induced inactivation. By coupling CPG-laccase with the TiO ₂/UV the degradation efficiency of 2,4-DCP was significantly increased as compared with the results obtained when immobilized laccase or TiO ₂/UV were separately used. Moreover, the enhancement was more remarkable for the degradation of 2,4-DCP with high concentration, such that for the degradation of 5mM 2,4-DCP, 90% removal percentage was achieved within 2h with the coupled degradation process. While for the TiO ₂/UV and CPG-laccase process, the removal percentage of 2,4-DCP at 2h were only 26.5% and 78.1%, respectively. The degradation kinetics were analyzed using a intermediate model by taking into account of the intermediates formed during the degradation of 2,4-DCP. The high efficiency of the coupled degradation process therefore provided a novel strategy for degradation of concentrated 2,4-DCP. Furthermore, a thermometric biosensor using the immobilized laccase as biorecognition element was constructed for monitoring the degradation of 2,4-DCP, the result indicated that the biosensor was precise and sensitive.