In this study, the catalytic performance of α-Fe2O3 in the low-dose ferrate (Fe(VI)) system was systematically studied through the degradation process of pentachlorophenol (PCP). The effects of several reaction conditions, including Fe(VI) dosage, α-Fe2O3 concentration, pH and inorganic ions, were comprehensively investigated. There was a quardratic function relation between [α-Fe2O3] and the pseudo first-order obvious rate constant (kobs) under low-dose Fe(VI), whose fitting equations were offered to predict the optimum catalyst concentration. The PCP degradation efficiency was inhibited with the solution pH=9.0, and the optimal pH was 7.0. Under the coexistence of common ions, Fe(VI)/α-Fe2O3 system still showed relatively good degradation capacity of PCP. Characterization and cycling experiments showed that α-Fe2O3 has good stability and recyclability. It was found that α-Fe2O3 directly mediated electron transfer in low-dose Fe(VI) oxidation process through the galvanic oxidation process (GOP) experiment, rather than inducing the generation of more reactive oxygen species or intermediate iron species. The catalytic mechanism was proposed based on nanocrystalline hematite, in which Fe(III) traps single electrons of contaminant molecules and the Fe(III)/Fe(II) pair conducts electrons as an electron carrier. Besides, two possible degradation pathways, single oxygen transfer and single electron self-coupling, were proposed for the degradation of PCP. Fe(VI)/α-Fe2O3 system mainly promotes the polymerization reaction. The study proved that PCP can be effectively removed by low-dose Fe(VI) added α-Fe2O3, which provides a new sight for developing Fe(VI) oxidation technology.

Insights into the high reaction efficiency of low-dose ferrate(VI) oxidation process catalyzed by α-Fe2O3 nanoparticles

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