Kinetic Studies on Black Light Photocatalytic Ozonation of Diclofenac and Sulfamethoxazole in Water

Black light photocatalytic ozonation of two pharmaceutical compounds, sulfamethoxazole (SMX) and diclofenac (DCF), and the resulting total organic carbon (TOC) are studied. DCF and SMX removals from some mg.L-1 to 100 mu g.L-1 are achieved in approximately 7 and 15 min ozonation, respectively, regardless of the ozone process, while the resulting TOC is eliminated via hydroxyl radical reactions. For initial concentrations lower than 50 mu g.L-1, competition between direct ozonation and hydroxyl radical oxidation to eliminate SMX and DCF takes place. The initial reaction period for cases of high and low concentration is simulated through fast-moderate and slow gas-liquid second order reaction kinetics, respectively. For high starting concentrations the calculated results suggest the presence of ozone fast reacting intermediates. For low starting concentration, calculated results indicate the importance of hydroxyl radical oxidation and the synergic effect of ozone and photocatalytic oxidation. Kinetic data of TOC ozonation, photocatalytic oxidation, and photocatalytic ozonation are also presented.