Enhancing degradation of sulfapyridine by magnetic Fe2O3-CoFe2O4@NC prepared through a facile solid phase coordination-calcination method for peroxymonosulfate activation

In this study, a facile and environmentally friendly solid phase coordination combined with calcination method was designed and ultra-efficient nitrogen carbon coated bimetallic composites (Fe2O3-CoFe2O4@NC) was fabricated to activate PMS for sulfapyridine (SPY) antibiotic elimination. A series of materials after calcined under different temperature and with different metal ratios were synthesized and Co/Fe carbon-based material calcined under 500 °C with 2:1 Co/Fe molar ratios (Fe2O3-CoFe2O4@NC) was demonstrated to be superior to rapidly remove 10 mg L−1 SPY within 10 min by activating 0.6 mM PMS. Meanwhile, the main reasons why different catalysts possessed different degradation efficiency were explored. The magnetic Fe2O3-CoFe2O4@NC showed a superior catalytic activity with kobs of 0.5314 min−1, which was 13.5-, 18.5- and 12.6 times than that of Co3O4@NC/PMS, Fe2O3@NC/PMS and CoFe/PMS systems, respectively. This was attributed to the synergistic effect of Co and Fe and accelerated electron transfer, which resulted in the generation of SO4−, 1O2, O2− and OH. The Fe2O3-CoFe2O4@NC/PMS system exhibited strong environment tolerance to most anions and humic acid, as well as high stability and recyclability. In detail, Cl−, NO3−, H2PO4− and humic acid (HA) showed promoting effect on SPY degradation, and the excellent removal efficiency maintained in actual water matrix. Moreover, the SPY degradation rate could reach 90 % after the fifth cycle and the mineralization rate was preferable, with 56.4 % of total organic carbon (TOC) removal rate. Generally, the degradation of SPY mainly involved bonds cleavage and hydroxyl addition, and five possible degradation pathways were proposed. This work provided an environmentally friendly, facile and promising route to synthesize nitrogen carbon coated bimetallic catalysts with sufficient properties for pollutant removal.