Aqueous tetracycline degradation by H2O2 alone: Removal and transformation pathway

The objective of this study was to investigate the degradation removal and pathway of tetracycline (TC) antibiotic from aqueous solution using H2O2 alone. Meanwhile, the effects of some operational parameters including initial concentration of H2O2 (29-580 mM), pH (3.3-10), and contact time (10-180 min) on the removal efficiency of TC were measured. The results showed that the removal of TC increased with increasing initial H2O2 dosage, pH and treatment time, and about 97% of TC was removed by H2O2 with the concentration of 174 mM in alkaline aqueous solution. Experiments with different scavengers indicated that TC degradation occurred via a direct molecular reaction instead of active radicals. Nine transformation products were identified, but only three ones were the final products. These products resulted from hydroxylation, loss of some functional groups and cleavage of benzene rings of TC. These results demonstrated a new oxidative transformation pathway of TC induced by H2O2 without combination, further supporting the important role of oxidant species in the environmental fate of TCs. (C) 2016 Elsevier B.V. All rights reserved.