Expeditious degradation of SMX by high-valent cobalt-oxo species derived from cobalt-doped C3N5-activated peroxymonosulfate with the assistance of visible light

Abstract

With excellent photoelectric properties and catalytic stability, carbon nitride and its derivatives are drawing increasing interest in persulfate activation for treating emerging pollutants in wastewater. In the present work, the synthesized cobalt-doped C3N5 (C3N5-Co) has well-defined surface properties and excellent performance in SMX degradation by activating peroxymonosulfate (PMS) with the assistance of visible light, and the removal rate can reach 99.57 % within 20 min. Moreover, the system shows superior operability over a wide pH range with promising catalytic stability and environmental suitability. Quenching experiments and EPR spectroscopic indicated that high-valent cobalt oxide (Co(IV)) species, SO4•-, •OH, O2•-, and 1O2 work in C3N5-Co0.59/PMS/SMX-vis combined system. The conversion of the oxidation product phenyl methyl sulfoxide (PMSO2) > 98 % using phenyl methyl sulfoxide (PMSO) as a probe agent demonstrated that high-valent cobalt oxide (Co(IV)) species as the major active species dominated the degradation process of SMX. The Co(II) species on the surface of C3N5-Co0.59 worked as a direct driver to rapidly and efficiently activate the PMS, producing various active species involved in the degradation process, while the photo-carriers generated by visible radiation act as another contributing force to regenerate Co(II) species and activate PMS. This study presented the heterogeneous C3N5-Co0.59/PMS/SMX-vis system is an effective strategy for the degradation of emerging pollutants and provides a promising novel ideal for the treatment of various organic pollutants in wastewater.