Iron electrode as efficient persulfate activator for oxcarbazepine degradation: Performance, mechanism, and kinetic modeling

In this study, electrochemically-activated persulfate (EC/PS) is proposed to degrade organic contaminants using oxcarbazepine (OXC) as a model compound. The results showed higher removal rates for OXC compared to persulfate alone, electrocoagulation alone, and the ferrous-activated persulfate (Fe2+/PS) process. A kinetic model regarding all of the reactive species was developed, and the model fitted the experimental data well. The second-order rate constants for OXC reacting with hydroxyl (OH) and sulfate (SO4(-)) radical were calculated to be 2.43 x 10(9) M-1 s(-1) and 3.55 x 10(8) M-1 s(-1), respectively, based on a relative rate technique. Both OH and SO4(-) substantially contributed to OXC degradation, whereas the contribution of SO4(-) was higher than that of OH. When the current density increased, the removal rates of OXC increased at low current densities and then decreased at high current densities. In particular, the degradation of OXC was significantly enhanced with increasing persulfate dosages. The pH affected the speciation of iron in solution, which in turn led to the poorly removal rate under alkaline conditions, whereas natural organic matter (NOM) dramatically inhibited the degradation of OXC by consuming OH and SO4(-) radicals. In addition, the efficient removal rates of para-chlorobenzoic acid, antipyrine, carbamazepine, and tetracycline under similar reaction conditions were also confirmed. Our results show the promising ability of the EC/PS system to control water pollution caused by organic contaminants. (C)2017 Elsevier B.V. All rights reserved.