Removal Efficiency And Kinetics Of Two Typical Antibiotics By UV Photolysis And Chemical Preoxidation In Water

Pharmaceuticals and personal care products(PPCPs) were often detected in water environments because of their wide use in some count ries around the world and their accumulation due to high biological activity and refractory nature. They could cause serious and chronic damages to ecological systems, aquatic organisms and human healt h. This study focused on two drugs, ranitidine and erythromycin, which were frequently detected in the water environments. Effects of ultraviolet photo-oxidation and potassium permanganate, sodium hypochlorite pre-oxidation, which were the commonly used in water treatment, have been investigated for the removal of the target pollutants, providing useful information on the removal of PPCPs in water treatment.(1) Ultraviolet oxidation could effectively remove ranitidine in water and ranitidine photocatalytic oxidation followed first order reaction. As ranitidine initial concentration increased, the removal efficiencies of ultraviolet oxidation were decreased. Solution pH also affected the removal efficiencies of ranitidine. At pH value of 5.5, ultraviolet photocatalytic oxidation of ranitidine removal efficiencies were higher than those on the neutral and alkaline conditions. In the presence of hydrogen peroxide, photocatalytic oxidation rate was significantly increased, however, it showed little effect on the final removal efficiencies. Based on the LC-MS/MS analysis, the degradation products were examined. The reactive functionalities of the ranitidine were mainly the terminal methyl, dimethyl amino groups and sulfide groups. The m/z ratio of the three corresponding types of major oxidation byproducts were 270,301 and 361, respectively. In the photocatalytic oxidation reaction process, disinfection by-products generated by ranitidine first increased and then decrease during chlorination. UV photolysis may break up the chains of ranitidine; as the continuation of UV irradiation, the loss of branched chain were mineralized, decreasing the disinfection by-products formation.(2) This study also investigated potassium permanganate and sodium hypochlorite oxidation removal of erythromycin, which is a widespread antibiotic in water environments. The experimental results show that sodium hypochlorite and potassium permanganate oxidation of erythromycin followed first order reaction. Between the two kinds of pre-oxidants, potassium permanganate had a better oxidation removing effect than sodium hypochlorite. Under different water treatment conditions, a high removal(> 70%) could be achieved after 30 min reaction time. The effects of initial concentrations of erythromycin, solution pH, water temperature and the dosage of two pre-oxidants on the removal efficiency were examined. The results show that as erythromycin initial concentration increased, the removal rates were decreased. The solution pH also affected the removal efficiencies of erythromycin. In the p H range of 5.5-8.0, the removal efficiencies of erythromycin decreased as the p H increased. Also, as the reaction temperature increased, the removal efficiencies of erythromycin were increased. Finally, as the the dosage of pre-oxidants increased, the removal efficiencies of erythromycin were also increased.