Sunlight activated ZnO mediated photocatalytic degradation of acetophenone in water

Solar photocatalysis is investigated as a potential advanced oxidation process for the removal of small amounts of acetophenone (ACP), a recalcitrant chemical pollutant detected in the effluent water from many petrochemical and other industries. Semiconductor oxide ZnO is used as the catalyst. The influence of various reaction parameters such as initial concentration of ACP, ZnO dosage, pH of the medium, humic acid, H2O2, O2, anions/salts etc on the rate of degradation is evaluated. 1hydroxy acetophenone (HACP) is identified as the major intermediate in the degradation. H2O2 formed insitu in the process acts as a reservoir of various reactive oxygen species (ROS) which can enhance the degradation. However, H2O2 also acts as a scavenger for the ROS leading to its own concurrent decomposition. Consequently, the enhancing effect of externally added H2O2 is not quite significant. The degradation is slow in deaerated system thereby reconfirming the role of O2 in the photocatalytic process. The catalyst can be recycled at least four times repeatedly before there is reduction in activity. Anions/salts inhibit the degradation mostly, though there is no consistency in their behaviour which depends on the concentration as well as reaction time. The study clearly shows that sunlight induced zinc oxide mediated photocatalysis can be used as a powerful tool for the degradation/mineralization of traces of ACP in contaminated water. Solar photocatalysis thus offers the potential for achieving the twin objectives of sunlight harvesting and wastewater treatment.