Degradation of bisphenol A by iron-carbon composites derived from spent bleaching earth

Abstract

A clay/carbon composite (SBE/C) was derived from waste of the edible oil refining industry, and iron-carbon composites (Fe-SBE/C) were successfully synthesized for the first time as a heterogeneous Fenton catalyst for bisphenol A (BPA) degradation. Because of the slow transformation between Fe2+ and Fe3+ on the Fe-SBE/C surface, the removal efficiency (only at the degradation stage) of BPA (or the total organic carbon (TOC)) in the heterogeneous Fe-SBE/C + H2O2 system was 78.0% (or 41.2%); this was much higher than the 42.5% (or 26.8%) of the homogeneous Fenton system. Also, there was a slow generation of hydroxyl radicals ( ·OH) on the Fe-SBE/C surface, and the removal efficiency of BPA (or TOC) for Fe-SBE/C was 20.9% (or 18.4%), which was much higher than the 5% (or 2.9%) for SBE/C. Less iron sludge was produced during the degradation process. Cl-, NO3-, and SO42- were scavengers of ·OH and had electrostatic attraction interactions with Fe-SBE/C, which led to the reduction of the BPA removal efficiency in the Fe-SBE/C + H2O2 system. Seventeen possible degradation intermediates of BPA in the Fe-SBE/C + H2O2 system were determined, and the degradation pathway was proposed. Various analytical methods were used to characterize the physicochemical properties of Fe-SBE/C. Free radical scavenging experiments confirmed that ·OH was the main active species of the Fe-SBE/C+H2O2 system, and the degradation mechanism was analyzed in detail. These results revealed that Fe-SBE/C has great potential for use in BPA removal in an aqueous environment.