Enhancing persulfate activation by carbon − based Mn − Fe nanoparticles for groundwater ISCO treatment: Efficiency, stability and mechanism

Abstract

Persulfate − based in situ chemical oxidation (ISCO) is a promising approach for groundwater treatment due to its potential. However, the development of catalysts with sufficient activity and stability in persulfate oxidation remains a long − term goal. In this study, we aimed to address this challenge by preparing bimetallic nanoparticles coated with porous nitrogen − doped graphene shells, known as MnFe − NC, to activate peroxydisulfate (PDS). The unique structural feature of MnFe − NC, with metallic crystal nanoparticles encapsulated in carbon shells, ensured excellent persulfate activation performance of MnFe − NC, even during repeated cycles and extended periods of storage. To evaluate the practical application of MnFe − NC, MnFe − NC/PDS was installed in sand columns for the ISCO of sulpiride (SPR), achieving removal efficiencies of approximately 100 % during a continuous 7 − day reaction process. MnFe − NC/PDS exhibited remarkable tolerance to pH changes and environmental interference commonly encountered in groundwater treatment scenarios. Combined with density functional theory calculations, Mn5C2 and Fe2N were identified as the key active site for MnFe − NC activation of PDS. The decomposition mechanism of SPR in the system was further analyzed, including the cleavage of C–N/C–C, denitration reaction, and substitution reaction. These findings provide important insights into the intricate processes involved in the degradation of refractory organic pollutants. The developed MnFe − NC catalyst for PDS − based ISCO exhibits great potential in the remediation of refractory organic pollutant − contaminated groundwater.