Hydrophilic mesoporous carbon as iron(III)/(II) electron shuttle for visible light enhanced Fenton-like degradation of organic pollutants

Abstract

A Fenton-like catalyst comprising of hydrophilic mesoporous carbon (HMC) and ferric ions was found very efficiently in degradation organic pollutants under visible light irradiation in the presence of H2O2. HMC with graphene domains and plenty of oxygen containing groups such as carboxyl groups can cooperate with ferric ions to form a visible light active Fe(III)-HMC configuration. Fe(III)-HMC showed obviously enhanced phenol degradation and mineralization efficiencies than that in dark condition. Acidic condition (pH = 3) is not only more superior in phenol degradation but also in iron leaching in comparison with the case at basic conditions (pH = 4.5–7.0) for Fe(III)-HMC. Total organic carbon (TOC) removal efficiency of five typical organic pollutants show that visible light active Fe(III)-HMC catalyst is more efficient than homogeneous Fenton reagents FeSO4/H2O2 excluding the temperature effect. Electron spin resonance (ESR) and electrochemical measurements reveal that the presence of active phenoxyl radicals and ligand to metal charge transfer (LMCT) facilitates the cycling of Fe(III)/Fe(II) and inhibit the side reaction via Haber-Weiss reaction. ·OH radicals rather than O2− and OOH were proved as the predominantly active oxidant. The proposed Fe(III)-HMC configuration activated by visible light opens up a new strategy for carbon based materials and iron species in Fenton-like chemistry.