Rapid removal of dyes under visible irradiation over activated carbon fibers supported Fe(III)-citrate at neutral pH

Activated carbon fibers supported ferric citrate (FeCit@ACFs) as a heterogeneous catalyst for the rapid removal of dyes under visible light irradiation is reported. The FeCit@ACFs/H2O2 system exhibited remarkable catalytic activity across a wide pH range (2-10). Moreover, the catalyst presented excellent sustained catalytic ability in these experiments. The effects of catalyst dosage, and H2O2 concentration were also evaluated. Electron paramagnetic resonance (EPR) spectroscopy confirmed the hydroxyl radicals ((OH)-O-center dot) involved as the active species in the catalytic system. Moreover, the superoxide radical (O-2(center dot-)) was not detected by EPR, suggesting better use of H2O2 for removal of dyes. According to the observed effects of the scavengers n-butanol and KI, hydroxyl radicals, especially the surface-bounded (OH)-O-center dot, had a dominant role in the oxidation of dyes. More importantly, the high adsorption capacity of ACFs could efficiently enhance the removal rate of dyes by the surface-bounded (OH)-O-center dot. This paper discusses a possible catalytic oxidation mechanism in the FeCit@ACFs/H2O2 system, which provides a feasible approach for the elimination of widely existing pollutants. (C) 2013 Elsevier B.V. All rights reserved.