Non-radical dominated degradation of chloroquine phosphate via Fe-based O-doped polymeric carbon nitride activated peroxymonosulfate: Performance and mechanism

The utilization of peroxymonosulfate (PMS)-based advanced oxidation process as a proficient approach for treating wastewater has garnered significant attention. However, the activation of PMS and the degradation of contaminants are highly dependent on or severely limited by the design and structured active sites of catalysts. Herein, an Fe-based O-doped polymeric carbon nitride catalyst, namely Fe-ONLH, was synthesized to activate PMS for the efficient removal of model pollutant chloroquine phosphate (CQP) via a non-radical dominant pathway with singlet oxygen (1O2). The rapid degradation of CQP in the developed Fe-ONLH/PMS system was achieved by the optimum degradation conditions predicted by Response Surface Method (RSM) and the catalyst dosage was considered to have the highest relative importance among the variables. Particularly, the ability of Fe and oxygen co-dopants to generate non-radical active species is mainly attributed to the various active sites on Fe-ONLH (e.g., Fe-O, graphite N, CO and NC-N2), which also exhibited advantages in adaptability of wide pH range, catalyst reusability, stability in complicated ionic environmental or water matrixes. Besides, probable intermediates and decomposition pathways of CQP attacked by non-radicals and radicals were analyzed. The current study provides new insights of Fe-base heterogeneous catalysts for PMS activation and non-radical pathway degradation of pollutants during wastewater treatment.