A novel strategy for efficient utilization of carbon residue from biomass gasification loaded NiCo2O4 to construct composite catalysts for activation of peroxymonosulfate to effectively remove antibiotics

Carbon residue (CR) derived from biomass gasification is a type of solid waste discharged from the biomass gasifier. CR is a carbon-rich material with a large specific surface area. Herein, NiCo2O4 nanoparticles were generated in situ on CR via a facile solvothermal method and the NiCo2O4-CR (NCCR) composite catalysts were prepared via solvothermal synthesis followed calcination method. The catalytic activity of NCCR was investigated by activating peroxymonosulfate (PMS) for the ciprofloxacin (CIP) degradation. The NCCR/PMS system exhibited the degradation efficiency, TOC removal efficiency, and removal reaction rate constant (k) of 93.86 %, 44.09 %, and 0.049 min−1 for CIP in 60 min, respectively, which were 1.17, 1.21 and 1.20 times of those in the NiCo2O4/PMS system, suggesting that CR had a positive impact on the improvement of the catalytic properties of NiCo2O4. Significantly, NCCR showed remarkable performance in terms of pH adaptation range, resistance to environmental disturbances, reusability, and other contamination applications. SO4•–, O2•– and 1O2,as the dominant reactive oxygen species, disrupt the molecular structure of CIP. PMS activation with NCCR mainly form free radicals and non-free radicals catalyzed by the redox couples of Co (III)/Co (II) and Ni (III)/Ni (II). Specially, Co (IV) = O also form and participate in the CIP degradation via a non-free radical pathway. Three possible degradation pathways of CIP were suggested by the degradation intermediates. The CIP degradation in the NCCR/PMS system was a process of reducing toxicity, protecting water ecosystem. The study provides a method to improve the catalytic properties of transition metal for activating PMS to purify antibiotic contamination wastewater, and opens a novel insight to deal with the solid waste from biomass gasification.