Encapsulating Fe-Co bimetal inside carbon aerogel to boost electron transfer for efficient heterogeneous electro-peroxone oxidation of organic pollutants

Abstract

We fabricated a novel Fe-Co bimetal encapsulated inside carbon aerogel sphere (Fe2Co@CS) to improve the electro-peroxone (EP) process. The degradation and mineralization of p-nitrophenol (p-NP) were 100% (15 min) with rate constant of 0.314 min−1 and 83.8% (60 min) in Fe2Co@CS/EP, respectively. Fe2Co@CS was composed of defective graphite carbon and Fe2Co alloy. The presence of metal–oxygen-carbon (M-O-C, MFe/Co) bonds promoted interface electron transfer from carbon layer towards Fe2Co alloy, which was advantageous to the reduction of ≡Fe3+/≡Co3+. Moreover, the Fe-Co synergistic effect also accelerated the interfacial catalytic reaction for activating O3 and H2O2. The quenching experiment and EPR test indicated that ·OH, ·O2- and 1O2 were main reactive oxygen species (ROSs). DFT calculations showed that O3 had lower adsorption energy on Fe2Co@CS than H2O2, manifesting that catalytic ozonation played the key role in ROSs generation. In addition, ozone utilization efficiency in Fe2Co@CS/EP (ΔTOC/ΔO3 = 1.23–0.68) revealed 66-36% increase relative to those of EP (0.74–0.5). Fe2Co@CS was an efficient catalyst over a wide pH range (3–11) with permissible iron and cobalt releases. The Fe2Co@CS/EP process exhibited high-performance for degrading different pollutants under high salinity condition with coexistence of Cl−, NO3− and SO42−. For treating real coal wastewater, the TOC removal was 52.7% at 4 h with low EEC (0.038 kWh (g TOC)−1). This study provided an efficient method for the development of EP in wastewater treatment.