Assessment of degradation behavior for acetylsalicylic acid using a plasma in liquid process

Acetylsalicylic acid (ASA) is a pharmacologically active compound. In this study, ASA was decomposed effectively using a plasma in liquid phase process with hydrogen peroxide and TiO₂ photocatalyst. Increasing the electrical power conditions (frequency, applied voltage, and pulse width) promoted plasma generation, which increased the rate of ASA decomposition. The added hydrogen peroxide increased the rate of ASA degradation, but injecting an excess decreased the degradation rate due to a scavenger effect. Although there was an initial increase in the decomposition efficiency by the addition of TiO₂ powder, the addition of an excessive amount inhibited the generation of plasma and decreased the degradation rate. The simultaneous addition of H₂O₂ and TiO₂ powder resulted in the highest degradation efficiency. We suggest that ASA is converted to salicylic acid through demethylation by hydroxyl radicals and is finally mineralized to carbon dioxide and water via 2,4-dihydroxy benzoic acid and low molecular acids.