RESUMO
Under the sunlight irradiation, the four common trace pollutants such as metronidazole, diclofenac, sulfamethoxazole and ibuprofen were degradated and mineralized by the hydroxyl radical (*OH) generated from decomposition of H2O2 catalyzed by ferrioxalate (FeOx), and the toxicity of the water solution containing degradated products and intermediates were evaluated. The factors affecting the removal of the TOC, such as the initial concentration of H2O2, FeOx, and the pH, were investigated through an indicator of total organic carbon. The disappearing rate of pollutants in aqueous solution was explained according to the chemical structure of the pharmaceuticals; the biotoxicity of the pharmaceuticals and the intermediates were evaluated by EC50 value of pharmaceutical solution to the Chlorella. The appropriate operating conditions were achieved at pH 3 with initial concentrations of 300 mg x L(-1) H2O2 and 75 mg x L(-1) FeOx at the conditions such as the initial concentration of four drugs were 20 mg x L(-1), respectively. The order of the degradation rate for the pharmaceuticals is metronidazole > ibuprofen > sulfamethoxazole > diclofenac. During the reaction, the biological toxicity increases with time and then decreases rapidly, along with appearance and disappearance of intermediates. Finally, a model on reaction mechanism was proposed, where Solar/FeOx/H2O2 system was used for the degradation of the pharmaceuticals with low concentration in aqueous solution.
