Effect of thermal and mechano-chemical activation on the photocatalytic efficiency of ZnO for drugs degradation

Over the past few years, pharmaceutical drugs have been considered as emerging pollutants due to their continuous input and persistence in the aquatic ecosystem even at low concentrations. They have been detected worldwide in environmental matrices, indicating their ineffective removal from water and wastewaters using conventional methods. In this study we present photocatalytic purification of water from Acetaminophen and Chloramphenicol by ZnO upon UV-light illumination. Commercial ZnO powders are activated thermally (annealed at different temperatures-100, 200, 300, 400 and 500 °C for 1 h) and mechanically (treated for 5, 15, 20, 30, 40 and 60 min). The mechonoactivation is performed varying the atmosphere in air, or in suspension of ethanol and methanol. The changes in the studied material (phase composition, structure and particle size of the samples) and morphology have been investigated by means of X-ray diffraction and Scanning electron microscopy. The ZnO powders annealed at 100 °C show highest photocatalytic efficiency and rate constant of dye degradation, which is due to the smaller size of nanocrystallites and their better developed surface. The degradation rate of Acetaminophen and Chloramphenicol increases with time of mechanical activation up to 30 min and then decreases. The optimal temperature and time of mechanoactivation are experimentally established.