Valorization of olive mill solid waste-derived biochar: An efficient approach for simultaneous adsorption and oxidation of micropollutant in surface water

Abstract

This study explores the utilization of olive mill solid waste (OMSW) as a source of biochar (BC) for effective removal of micropollutants during surface water treatment. The conversion of OMSW into BC was accomplished via pyrolysis conducted at varying temperatures ranging from 400 to 600 °C. To improve its performance, BC was subjected to activation through either physical-thermal or chemical techniques. BC samples were characterized by SEM microscopy revealing a porous structure, surface area analysis showed an increase in surface area for biochar samples subjected to physical-thermal activation (BC-T) (20 m2/g) and chemical activation using potassium hydroxide (BC-KOH) (70 m2/g) or zinc/iron (BC-Zn/Fe) (456 m2/g). The zero point of charge range from <3 to 4.2 for the different BC samples whereas FTIR measurements showed that physical activation at 900 °C favors a graphitic structure in BC.The catalytic properties of the biochar samples were investigated in the activation of sodium persulfate (PSF) for the oxidation of micropollutants (MPS), including ciprofloxacin (CPX), sulfamethoxazole (SMZ), and paracetamol (PCM), in natural Lake Kinneret water. BC-KOH exhibited the highest removal efficiency, and the removal of MPS increased with higher dosages of BC and PSF. Under optimized conditions ([biochar]: 500 mg/L and [PSF]: 200 mg/L), significant removal efficiencies were achieved for PCM (88.2 % ± 0.7), CPX (80.8 % ± 1.9), and SMZ (64.1 % ± 3.2) after a 5-hour treatment. Finally, MPS adsorbed on BC experienced significant surface oxidation, resulting in removal efficiencies for PCM (97.9 %), CPX (92 %), and SMZ (77.9 %). This oxidation process is expected to enhance the treatment effectiveness prior to regeneration.