Waste Pet Plastics Derived Carbon-Anchored Single-Atom Iron Catalyst for Highly Selective Singlet Oxygen Generation Towards Efficient Degradation of Organic Pollutants

Abstract

Advanced oxidation processes (AOPs) have been recognized as highly effective techniques for the rapid degradation and mineralization of persistent organic pollutants (POPs), surpassing the performance of conventional technologies. Among these methods, single-atom catalysts (SACs) have garnered increasing attention in wastewater treatment due to their outstanding catalytic efficiency. Optimizing the coordination environment of SACs and designing structures with enhanced exposure of active sites are promising strategies to improve the activation of peroxymonosulfate (PMS). In this study, cost-effective waste polyethylene terephthalate (PET) plastics were employed as a carbon source, undergoing "controlled carbonization" facilitated by a ZnCl2/NaCl eutectic salt mixture to synthesize a simple and economical single-atom iron catalyst (Fe-SA/NPC) for PMS activation. The optimized system (0.5 Fe-SA/NPC/PMS) exhibited remarkable catalytic performance against the model antibiotic tetracycline (TC), achieving an approximate 80% removal rate within just 30 minutes, even in the presence of complex environmental interferences. The system also generated significant levels of the electrophilic species singlet oxygen (1O2). Reactive oxygen species (ROS) analyses revealed that Fe-SA/NPC exhibited high selectivity for 1O2 production via PMS activation. Furthermore, density functional theory (DFT) calculations confirmed that the single Fe atom serves as the primary active site, facilitating the conversion of PMS to 1O2. The generated 1O2 at the Fe site directly degrades TC adsorbed on the nitrogen-coordinated sphere, thereby enhancing decontamination efficiency. This study adopts a unique approach to effectively explore a novel and efficient solution for recycling PET plastic waste, and is well-connected to the technical characteristics of SACs. It offers substantial technical support for the practical integration of SACs into organic wastewater treatment and provides valuable theoretical guidance.

Keywords: Waste polyethylene terephthalate plastics, Molten salt assisted pyrolysis, Single-atom Fe catalysts, Singlet oxygen, Fenton-like chemistry