Mechanistic investigations in sonochemical degradation of trihalomethanes in presence of non–porous and mesoporous silica nanospheres

This study reports mechanistic investigations in sonochemical degradation of four Trihalomethanes (THMs), viz. CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃, in presence of non–porous and mesoporous silica nanospheres. Degradation reactions of THMs were carried out under identical conditions with addition of silica nanospheres. Concurrently, simulations of cavitation bubble dynamics were carried out. Mesoporous silica nanospheres with the largest surface area and the highest mean pore diameter yielded the highest enhancement in degradation of the THMs. These results were also corroborated by H₂O₂ dosimetry. The concentration profiles of the THMs were fitted to pseudo 1st order kinetic model. Although mean pore sizes of mesoporous silica nanospheres were smaller than minimum threshold radius for transient cavitation, these nanospheres provided surface-induced and pore-induced nucleation to augment cavitation bubble population in medium. The highest nanosphere–induced enhancement in degradation was obtained for CHBr₃, while the highest total degradation was obtained for CHCl₃. With concurrent analysis of experimental and simulations results, an attempt is made to deduce the predominant physical mechanism of degradation of the THMs.