Heterogeneous advanced photo- Fenton process using peroxymonosulfate and peroxydisulfate in presence of zero valent metallic iron: A comparative study with hydrogen peroxide photo-Fenton process

The present research work has demonstrated the use of zero valent metallic iron (Fe-0) in the photoFenton process under the UV illumination as a promising and novel technique. Oxidants like oxone a peroxymonosulfate (PMS) and ammonium persulfate a peroxydisulfate (PDS) were used in comparison with classical hydrogen peroxide (HP). PMS was found to be a better oxidant in comparison with HP and PDS at higher pH conditions especially in the pH range of 5-7. PMS acts as better oxidant with dipolar unsymmetrical structure, higher oxidation potential and its lower LUMO energy can easily accept electrons more readily compared to the other two oxidants. The degradation rate for various oxidation processes at pH 3 shows the following decreasing order: Fe-0 /PMS/UV approximate to Fe-0 /HP/UV > Fe-0 /PDS/ UV > HP/UV > PDS/UV > PMS/UV > Fe-0 /PMS/dark > Fe-0 /HP/dark > Fe-0 /PDS/dark > Fe-0 /UV > Fe-0 /dark. At pH 5, PMS/UV and PDS/UV systems show similar efficiencies as Fe-0 /PMS/UV and Fe-0 /PDS/UV process, since most of the Fe-0 surface is covered by the precipitates of hydroxide and oxyhydroxides. Though recycling capability of iron powder is almost comparable for first to fifth repetitions, Fe-0 retains its recycling capability better in the presence of HP for the further runs rather than PDS and PMS. (C) 2016 Elsevier Ltd. All rights reserved.