Enhanced removal of emerging contaminants using persulfate activated by UV and pre-magnetized Fe0

Emerging contaminants (ECs) have been frequently detected in the aquatic environment and have adverse effect on the environment. In our present study, four ECs (800 mu gL(-1) oxytetracycline (OTC) and tetracycline (TC); 400 mu gL(-1) sulfadiazine (SD) and sulfamethazine (SMT)) spiked into the secondary wastewater effluent (SWE) were treated by novel UV/pre-magnetized Fe-0/PS process (UV/pre-Fe-0/PS). TC, OTC and SMT could be completely removed within 30 min and 98.4% SD could be removed within 60 min, while less than 10%, 20% and 60% ECs could be removed by Fe-0/PS, pre-Fe-0/PS and UV process within 60 min. Synergetic factor values (6.1-12.3) in UV/pre-Fe-0/PS were much larger than in UV/Fe-0/PS (2.3-5.4) to remove various ECs, achieving 0.7-2.2 times enhancement in degradation rate constants and 45%-86% reduction in treatment costs. EPR spectra and scavenging tests by tert-butyl alcohol and methanol confirmed that not only faster and more SO4 center dot- and % OH radicals were produced but also their contributions to SMT removal were enhanced. Optimization of dosage of Fe-0 (0-0.4 mM) and dosage of PS (0-0.4 mM) indicated that 0.2mM Fe-0 and 0.2mM PS was the optimal dosage. Meanwhile, this process not only could enhance 0.7-15.8 times degradation rate constant but also could reduce about 14.3-97.9% costs to remove various ECs compared with US/Fe-0/PS, ozonation, VUV/UV/Fe3+ and UV/H2O2 process. Moreover, it could enhance 1.4 times of degradation rate constant and reduce about 62% cost to remove SMT in another SWE, indicating the applicability in different wastewaters. Therefore, UV/pre-Fe-0/PS process is promising and cost-effective to remove ECs in SWEs.