Insights into the O generation of activation of persulfate by zinc ferrite loaded on oxalic acid-modified activated carbon: Interface mechanism and molecular dynamics.

Developing carbonaceous composites with strong non-radical activity and recyclability is key for sustainable wastewater purification. Herein, a novel photocatalytic process was designed using zinc ferrite loaded on oxalic acid-modified powdered activated carbon (ZFO/OA/PAC) to activate persulfate (PDS) under visible light (VL) irradiation. ZFO was in-situ grown onto OA/PAC via C=O bridging, forming stable Zn/Fe-O-C bonds that suppressed magnetic agglomeration and enabled directional electron transfer. The optimized interfacial binding energy of 22.45 kcal/mol reduced the activation energy barrier, enhancing active site utilization and reaction kinetics through efficient electron cycling. With a narrow bandgap of 1.54 eV, 0.1 g/L ZFO/OA/PAC and 0.1 g/L PDS achieved 94.3 % tetracycline (TC) removal under VL, with a kinetic constant 23.75 times higher than pristine ZFO. The process predominantly generated h and O, the latter arising from superoxide conversion, PDS-induced functional group transformation, and oxygen-vacancy-mediated electron transfer. Photocatalysis also promoted Fe(III)/Fe(II) cycling, further aiding reactive oxygen species (ROS) formation. Seventeen intermediates were identified, with degradation and detoxification proceeding mainly through ring-opening, substitution, and ROS-driven molecular reconstruction. The magnetic ZFO/OA/PAC exhibits broad organic pollutants' removal capability and effective adaptability to real water matrices. This work provides a paradigm for designing magnetic carbonaceous photocatalysts to leverage non-radical pathways, advancing scalable wastewater purification technologies.