One-pot preparation of surface vulcanization Co-Fe bimetallic aerogel for efficient sulfadiazine degradation

Abstract

• Persulfate activation of CoFe-0.2S aerogels improves with increasing S content. • Synergy of cobalt-iron is conducive to accelerate the generation of radicals. • Delocalized electrons in surface FeS n accelerate electron transfer of PDS activation. • Proposed reaction pathway for the oxidation of sulfadiazine. A novel magnetic surface vulcanized cobalt-iron aerogel (CoFe-S MA) with a self-supporting, crosslinked bimetallic nanowire structure was fabricated via NaBH 4 -mediated gelation followed by in-situ vulcanization with Na 2 S solution, which showed efficient sulfadiazine (SDZ) degradation through peroxodisulfate (PDS) activation. The optimized CoFe-0.2S aerogels exhibited the best degradation performance (99.8%) for SDZ (10 mg/L, 100 mL) within 15 min, and the total organic carbon (TOC) removal efficiency reached 53%. The excellent degradation performance was attributed to the accelerated redox process and rapid formation of sulfate radical (SO 4 ·- ) caused by bimetal synergistic effect, as well as the sufficient exposed active sites provided by the self-supporting hierarchical porous structure of the aerogel. Compared with CoFe-MAs, electrochemical impedance spectroscopy (EIS) demonstrated lower resistance and more rapid charge transfer of CoFe-S MAs, which was ascribed to the presence of delocalized electrons in iron sulfides layer. A high turnover frequency (TOF) of 4.0 L∙min −1 ∙g −1 was achieved due to that the reduction effect of S 2- on the surface promoted the regeneration of Fe and Co active species. Electron paramagnetic resonance (EPR) and quenching experiments revealed the dominant reactive oxide species (ROS) to be SO 4 ·- , ‧OH, and Fe (Ⅳ). This work paves the way for the application of metal aerogels in the field of advanced oxidation process based on sulfate radical (AR-AOPs).