Printing and dyeing sludge derived biochar for activation of peroxymonosulfate to remove aqueous organic pollutants: Activation mechanisms and environmental safety assessment

Printing and dyeing sludge (PADS) is considered hazardous waste and difficult to dispose of. Traditional sludge disposal technologies lead to land occupation and dioxin generation, as well as the lack of resource utilization of sludge. In this study, PADS biochar was prepared by pyrolysis technology and used as a peroxymonosulfate (PMS) activator to remove organic pollutants in water for the first time, and the safety of its use was evaluated. The results showed that PADS biochar prepared under optimized conditions of 800 °C for 1.5 h (BC-800-1.5) could efficiently activate PMS and achieve 99% removal of bisphenol A (BPA) within 20 min which was more efficient than BC-800-1.5 adsorption alone (12%) and oxidation by single PMS (4%). Radical trapping experiments suggested that 1 O 2 -dominated non-radical activation pathway was responsible for BPA degradation. By further characterization, C O, graphite nitrogen and pyridine nitrogen on the PDAS surface were identified as active sites for PMS activation. The results of safety evaluation experiment showed that the content of polycyclic aromatic hydrocarbon in BC-800-1.5 and heavy metals leached from BC-800-1.5 were well within the corresponding standards. This research had developed a new technological approach to simultaneously realize the resource utilization and eliminate the environmental hazards of PADS sludge.