Calotropis gigantea fiber confined ZIF-67 derived Co, N in-situ assembled hollow carbon fiber to activate peroxymonosulfate for degradation of perfluorooctanoic acid

Abstract

Perfluorinated compounds have serious impacts on ecosystems and threats to human health, and exploring technologies to remove them is urgently needed. Using Calotropis gigantea fiber (CGF) as the biological template, the precursor of ZIF-67 was firstly in-situ anchored in the inner/outer walls of the fiber and then pyrolyzed to yield the composite catalyst labelled as Co/C@C. In combination with peroxymonosulfate (PMS), the advanced oxidation system, i.e. Co/C@C/PMS, was constructed for the catalytic removal of perfluorooctanoic acid (PFOA) from water. The experimental results showed that under the optimized conditions of PMS dosage of 1.0 g/L, catalyst dosage of 0.5 g/L and pH 3.0, PFOA achieved the degradation efficiency of 72.2% within 4 h at ambient temperature. Combined with free radical quenching, electron paramagnetic resonance, electrochemistry and nitroblue tetrazolium dichloride-based UV-Vis analysis, the reactive oxygen species and diverse pathways were identified, including SO4•−, O2•−, O21 and electron transfer process in the Co/C@C/PMS system. The coexisting anions (HCO3−, Cl−, H2PO4− and NO3−) and real wastewaters showed no significant effects on PFOA degradation, demonstrating that the Co/C@C/PMS system has good resistance to external ions and different media. After four cycles, the degradation efficiency of PFOA was still 62.8%, indicating that Co/C@C has high stability and good reusability. The degradation products of PFOA were mainly short-chain perfluorinated carboxylic acids (C4-C7) and hydrogen-substituted perfluorinated compounds. Based on quantitative structure-activity relationship analysis, their ecotoxicity was finally evaluated via ECOSAR method. In short, natural CGF derived Co/C@C has great potential for the reduction of emerging PFOA to achieve a sustainable water environment for humans.