Reutilization of waste self-heating pad by loading cobalt: A magnetic and green peroxymonosulfate activator for naphthalene degradation

The disposal and recovery of solid wastes and the remediation of polycyclic aromatic hydrocarbons (PAHs) are the key issues of environmental pollution control. In this study, micro cobalt loaded on iron-carbon-vermiculite composite (Co-ICV) was prepared for the first time by the reutilization of waste self-heating pad as a carrier of cobalt catalyst, which exhibited better performance than bulk cobalt catalyst in peroxymonosulfate (PMS) activation for the degradation of naphthalene (NAP) in water. Above 98% of NAP (2.0 mg/L) was effectively eliminated within 15 min by the Co-ICV (0.2 g/L) activated PMS (0.5 mmol/L) in a pH range of 5.0-9.0. High magnetism and very limited cobalt leaching realized the convenient separation and stable reusability of Co-ICV. Mechanism investigation indicated that Co(II) species were the main active sites to activate PMS decomposition for the generation of SO4•- and •OH, contributing to the rapid degradation of NAP. Meanwhile, the NAP degradation pathways were deduced via combining the identification of intermediates and the calculation of frontier electron densities (FEDs). Furthermore, the ability of the Co-ICV/PMS system for the NAP degradation in actual lake water and the removal of other refractory pollutants demonstrated that the combination of Co-ICV and PMS was a prospective method for the removal of PAHs. Overall, Co-ICV is a green and promising activator of PMS, and the future development will provide more insights into the comprehensive utilization of solid wastes for the remediation of wastewater containing PAHs.