Heterogeneous Photodegradation of Pentachlorophenol and Iron Cycling with 1

10 Heterogeneous photodegradation of pentachlorophenol (PCP) in the goethite 11 (α-FeOOH) and hematite (α-Fe2O3) systems with oxalate under UVA illumination was 12 investigated. The PCP degradation, dechlorination and detoxification, in terms of 13 Microtox acute toxicity, were achieved to the higher efficiency in the hematite 14 suspension than in the goethite suspension. The optimal initial concentration of oxalic 15 acid (Cox) for the PCP degradation with goethite and hematite under the experimental 16 conditions was found to be 1.2 mM, since sufficient Fe(III) as Fe(C2O4)3 and Fe(II) as 17 Fe(C2O4)2 can be formed at Cox≥1.2 mM. The main intermediates of PCP degradation 18 were identified through GC-MS, HPLC and IC analyses. It was found that the cycling 19 process between Fe(III) and Fe(II) in both the goethite and hematite systems occurred 20 more vigorously at the initial stage and gradually became gentle, while the rate of PCP 21 photodegradationvaried from fast to slow during the reaction time. furthermore, the 22 formation of H2O2 during photoreaction was also studied to explore its effects on the 23 photodegradation and the iron cycling processes. 24