Enhanced photo-degradation of paracetamol on n-platinum-loaded TiO2: The effect of ultrasound and OH/hole scavengers

Elimination/mineralization of paracetamol (PCT) was investigated by catalytic oxidation under ultrasound, UV and both. The catalyst was synthesized by immobilization of nPt on TiO2 to benefit from the ability of Pt to facilitate charge transfer processes and to separate e−/h+ pairs. It was found that increasing the Pt-loading enhanced the rate of sonochemical reactions, but retarded that of photolytic reactions, due to reduced UV absorption on the surface. Simultaneous application of sonolysis and photolysis was synergistic due to disaggregation of the particles and homogenization of the active species over the catalyst surface. The decay of PCT was highly dependent on the availability of OH, as the reactions were nearly terminated in the presence of a strong OH scavenger-2-propanol. However, a remarkable rate enhancement was observed in the presence of a suitable dose of I−, which scavenges both OH and hvb+. The result was explained by the production of excess radicals upon sonolysis of iodide solutions, and the reactivity of PCT with them. Finally, carbon mineralization was significantly hindered in the presence of both scavengers due to increased competition for OH and inefficient formation of hydroquinone arising from reduced availability of hvb+.