Degradation of diclofenac by pyrite catalyzed Fenton oxidation

We demonstrated that diclofenac can be rapidly and completely oxidized in Fenton reaction system using pyrite as catalyst. The pH of the solution dropped from 5.7 to 4.1-3.2 with addition of different amounts of pyrite (0.5-4.0 mM) as Fe(II) concentration increased to 0.07-0.52 mM. Complete degradation (100%) of diclofenac was observed by pyrite Fenton system within 120 s, while only 65% of diclofenac was removed by classic Fenton system in 180 s. Degradation of diclofenac was significantly inhibited (100-51%) by addition of HO center dot scavenger (t-butanol) but not by O-2(center dot-) scavenger (chloroform), indicating that diclofenac was dominantly oxidized by HO center dot produced during pyrite Fenton reaction. It was suggested that continuous dissolution of aqueous Fe(II) by pyrite Fenton reaction supported the complete degradation of diclofenac. The rate of diclofenac degradation increased as pyrite and H2O2 concentrations increased. 2,6-dichlorophenol, 2-chloroaniline, and 2-chlorophenol were detected as major intermediates but they were rapidly degraded in 120 s. Chloride ions, ammonium, and total organic carbon measurements confirmed that diclofenac finally degraded to further oxidized forms (organic acids, HCl, and CO2). (C) 2012 Elsevier B.V. All rights reserved.