Enhancement of Fe@porous carbon to be an efficient mediator for peroxymonosulfate activation for oxidation of organic contaminants: Incorporation NH2-group into structure of its MOF precursor

Abstract

Metal-organic frameworks (MOFs) derived metal@porous carbon showed good performance in peroxymonosulfate (PMS) activation for refractory organic chemical degradation from aqueous. However, the effect of structure and physical-chemical properties of metal@porous carbon on PMS activation and its involved reaction mechanism were still unclear. Herein, Fe@porous carbon derived from MOF MIL-53(Fe) was used as target, to discuss the role of NH2-group incorporation on the development of structure and physical-chemical properties of obtained Fe@porous carbon, and reaction mechanism for PMS activation. The incorporation of NH2-group significantly decreased the synthesis temperature of Fe@porous carbon and increased the encapsulation of Fe0 in the porous carbon. Furthermore, the addition of nitrogen in porous carbon and rigid encapsulation structure reduced the defects of the Fe@porous carbon. These improvements of the structure and chemical properties were favored for enhancement of the catalytic activity and stability of the obtained Fe@porous carbon in the activation of PMS. Electron paramagnetic resonance (EPR) experiments indicated that SO4−, OH and 1O2 were involved. The radical pathway involving SO4− and OH was the prevailing pathway while the nonradical pathway involving 1O2 was the recessive pathway. Based on intermediate identification, the degradation pathway of acyclovir (ACV) was proposed as SO4− and OH derived process, and eight of intermediates were first reported. It was interesting to note that iron species, carbon structure, and nitrogen element in the catalysts derived from MIL-53(Fe) or NH2-MIL-53(Fe) clearly showed different role and reaction pathway. This work not only provided an efficient Fe@N-doped porous carbon for activation PMS to degrade refractory organic chemicals for water purification, but also suggested a valuable insight for the design of metal@porous carbon derived from MOF.