Co3O4 decoration on iron-contained biochar composite fabricated by co-pyrolysis of red mud and spent coffee ground: A synergistic hybrid for Rhodamine B degradation via peroxymonosulfate activation

Abstract

In this study, a composite was prepared by co-pyrolysis of red mud (RM) and spent coffee grounds (SCG). Then, cobalt was incorporated in the as-prepared RM/biochar composite (RMBC) and employed as the heterogeneous activator of peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. A temperature-programmed reaction and X-ray diffraction (XRD) measurements disclosed that the hematite (Fe2O3) phase in RM experienced a step-wise reduction to magnetite (Fe3O4) and Fe0 with increasing temperature during the co-pyrolysis of RM and SCG. The RMBC exhibited low performance for PMS activation to degrade RhB. However, incorporating 1.5 wt% Co can drastically improve the catalytic performance. The influence of initial pH, catalyst dosage, initial RhB concentrations, and temperature on the degradation efficiency was investigated. The quenching experiments combined with electron paramagnetic resonance analysis proved that the ·OH and SO•−4radicals, and 1O2 no-radical were the main reactive species for RhB degradation in the Co3O4/RMBC/PMS system.