Prussian blue analog-derived Fe-Mn oxides for the enhanced activation of persulfate in sulfadiazine degradation: radical generation mechanism and electron transfer

Advanced oxidation processes, especially those engaging in persulfate activation, are one of the emerging technologies for the degradation of recalcitrant organic pollutants. This study used Fe and Mn-loaded Prussian blue analogs (FeMn-PBA) as precursors to synthesize a nitrogen-doped graphene shell (FeMn@NG) through calcination in a nitrogen atmosphere. This was then employed as a catalyst to initiate the degradation of sulfadiazine (SD) using persulfate. The encapsulated FeMn bimetallic nanoparticles with various oxidation states undergo redox cycling, which promotes the rapid generation of free radicals and maintains the stability of FeMn@NC by sustaining continuous persulfate (PDS) activation. The results showed that nearly 96 % of SD was degraded within 45 min. Experiments involving free radical quenching and electron paramagnetic resonance spectroscopy demonstrated that sulfate radicals (SO₄^·−) and superoxide radicals (O₂^·−) were primarily responsible for the degradation of SD. The impact of different process parameters on the degradation efficiency of SD was simultaneously investigated. The degradation products of SD were examined, and a degradation pathway was proposed according to the LC-MS findings. XPS analysis indicated the presence of Fe/Mn redox cycling, which played a role in the equilibrium electron transfer during PDS activation. This study provides insights into the rational design of efficient catalysts by combining Prussian blue analogs with FeMn, while also promoting the remediation of polluted water bodies.