Microwave (MW)-assisted design of cobalt anchored 2D graphene-like carbon nanosheets (Co@GCNs) as peroxymonosulfate activator for tetracycline degradation and insight into the catalytic mechanism

Developing a rapid and cost-effective strategy to design catalysts for advanced oxidation processes (AOPs) has significant implications for environmental remediation. In this study, cobalt anchored 2D graphene-like carbon nanosheets (Co@GCNs) catalysts were fabricated by simple coordination of metal precursors into agarose through microwave (MW)-assisted method to activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. Among them, the Co@GCN-1 exhibited excellent dispersibility and catalytic performance. The Co@GCN-1/ PMS system could completely degrade TC (20 mg L-1) within 20 min, whose reaction rate constant (0.273 min(-1)) was about 6.5 times that of the Co3O(4/)PMS system (0.0362 min(-1)) and 14.1 times of the GCN/PMS system (0.0194 min(-1)), respectively. Additionally, the degradation performance was applicable in a wide pH range (3.84-9.03) and still reached an efficiency of>90% after five cycles. Non-radical pathway represented by O-1(2) served as the main contributor to TC degradation besides radicals (i.e., SO4 center dot-, (OH)-O-center dot, and O-2(center dot-)). Density functional theory (DFT) calculations unveiled the synergistic interaction of Co@GCNs, where 2D GCNs as electron mediators promoted the Co3+/Co2+ cycle. Based on the LC-MS analysis, three main degradation pathways of TC including fourteen possible intermediates were proposed based on different ROS reactions. This work provides a facilely prepared and promising 2D metal-based carbonous catalyst to activate PMS for the efficient degradation of TC.