Insight into Peroxymonosulfate Activation Catalyzed by Fe/Mn Bimetallic-Loaded In Situ Nitrogen-Doped Biochar: the Critical Role of Singlet Oxygen and Superoxide Radicals

Water pollution caused by emerging contaminants poses significant environmental and health risks, while the management of invasive algal biomass remains an underutilized resource. This study presents a novel Fe/Mn-modified in situ N-doped Enteromorpha prolifera-derived biochar catalyst (Fe/Mn/EP), addressing the dual challenges of efficient peroxymonosulfate (PMS) activation and utilization of invasive algal biomass. Through a straightforward one-step pyrolysis approach, the obtained catalyst integrated nitrogen functionalities and bimetallic active sites, enabling it to achieve an outstanding catalytic performance. It completely degraded carbamazepine (CBZ) in water samples within 30 min. The degradation process relied on the synergy between radical and nonradical pathways, primarily dominated by singlet oxygen (1O2) and superoxide radicals (·O2–). Specifically, in situ nitrogen doping, particularly involving pyrrole and graphite nitrogen, enhanced PMS activation by regulating the electronic properties and increasing the density of active sites. The degradation of CBZ significantly reduces the toxicity of the system by analysis prediction based on quantitative structure–activity relationship. The Fe/Mn/EP catalyst demonstrated broad adaptability across various emerging pollutants and real water matrices. This work highlights a sustainable strategy to transform problematic algae into high-performance biochar-based catalysts, offering a scalable solution for water pollution remediation.