Non-radical oxidation of TBBPA and TBBPS in soil using Fe and Cu co-doped sulfurized carbon nitride: A comparative study of peroxymonosulfate and peroxydisulfate activation

The non-radical oxidation pathways in persulfate-based advanced oxidation processes (PS-AOPs) offer significant potential for soil and groundwater remediation. However, the construction of non-radical systems and the underlying reaction mechanisms remain insufficiently understood. In this study, Fe and Cu co-doped sulfurized carbon nitride (FeCuS@GFs) were distributed on the surface of graphite felt for non-radical oxidation pathways. FeCuS@GFs activated peroxydisulfate (PDS) and peroxymonosulfate (PMS) to generate electron transfer process and Fe(IV) active species as the primary non-radical oxidation pathways, respectively. FeCuS@GFs exhibited high efficiency in removing tetrabromobisphenol A (TBBPA) and tetrabromobisphenol S (TBBPS) from aqueous matrices. Comparative analysis demonstrated that Fe(IV) active species exhibited higher reactivity than electron transfer process for degrading TBBPA/S. Density functional theory (DFT) calculations and experiments further revealed that TBBPS was more resistant to non-radical oxidation than TBBPA. Additionally, soil properties, including pH, Fe-containing minerals and organic matter, influenced the efficiency of electron transfer processes and Fe(IV) active species. FeCuS@GFs/PMS system achieved nearly complete removal of TBBPA/S from various soil samples, highlighting its superior applicability for soil and groundwater remediation. This study provides novel insights into the role of non-radical oxidation pathways in their potential for actual soil and groundwater treatment.