Cobalt-modified catalyst derived from cold-rolled sludge for phenol degradation via PMS-activated fenton-like reaction: Performance and mechanistic investigation.

To address the dual challenge of rapid increase in industrial solid waste and presence of organic pollutants in water bodies, this study proposes a "waste-to-treat-waste" synergistic strategy for resource utilization, in which cold-rolling sludge and spent lithium-ion battery cathode materials are innovatively converted to a high-performance Co/Fe/N-codoped carbon-based catalyst (0.05Co@FC-4). The results show that this catalyst exhibits excellent performance in activating peroxymonosulfate (PMS) for phenol degradation, achieving complete removal of phenol within 10 min and maintaining a broad pH tolerance (3-10). Multiple characterization techniques confirm that the introduction of Co leads to the formation of highly dispersed CoFe oxide nanoparticles and optimizes the electronic structure of the catalyst, as shown by higher Fe2+/Fe3+ and Co3+/Co2+ ratios; this significantly promotes the redox cycling between metal active sites and enhances the PMS activation efficiency. Mechanistic investigations further reveal that this system follows a non-radical pathway dominated by singlet oxygen (1O2), which effectively explains its high activity in complex water matrices. In addition, toxicity assessment of the degradation intermediates confirm that phenol can be mineralized to harmless products. This work not only presents a feasible approach for high-value utilization of two hazardous solid waste sources, but also provides new insights into the development of sustainable environmental remediation technologies through the design of efficient and stable catalysts.