How Nitrogen and Sulfur Doping Modified Material Structure, Transformed Oxidation Pathways, and Improved Degradation Performance in Peroxymonosulfate Activation

Abstract

Current research has widely applied heteroatom doping for the promotion of catalyst activity in peroxymonosulfate (PMS) systems; however, the relationship between heteroatom doping and stimulated activation mechanism transformation is not fully understood. Herein, we introduce nitrogen and sulfur doping into a Co@rGO material for PMS activation to degrade tetracycline (TC) and systematically investigate how heteroatom doping transformed the activation mechanism of the original Co@rGO/PMS system. N was homogeneously inserted into the reduced graphene oxide (rGO) matrix of Co@rGO, inducing a significant increase in the degradation efficiency without affecting the activation mechanism transformation. Additionally, S doping converted Co3O4 to Co4S3 in Co@rGO and transformed the cooperative oxidation pathway into a single non-radical pathway with stronger intensity, which led to a higher stability against environmental interferences. Notably, based on density functional theory (DFT) calculations, we demonstrated that Co4S3 had a higher energy barrier for PMS adsorption and cleavage than Co3O4, and therefore, the radical pathway was not easily stimulated by Co4S3. Overall, this study not only illustrated the improvement due to the heteroatom doping of Co@rGO for TC degradation in a PMS system but also bridged the knowledge gap between the catalyst structure and degradation performance through activation mechanism transformation drawn from theoretical and experimental analyses.

Density Functional Theory and Machine Learning-Based Quantitative Structure–Activity Relationship Models Enabling Prediction of Contaminant Degradation Performance with Heterogeneous Peroxymonosulfate Treatments

“…Our previous work has demonstrated that CoS is more likely to generate 1 O 2 , whereas Co 3 O 4 is more likely to generate • OH and SO 4 –• radicals . With different catalysts in PMS heterogeneous activation, the degradation mechanisms of the contaminants vary because there are different active species present.…”

“…Our previous work has demonstrated that CoS is more likely to generate 1 O 2 , whereas Co 3 O 4 is more likely to generate • OH and SO 4 −• radicals. 34 With different catalysts in PMS heterogeneous activation, the degradation mechanisms of the contaminants vary because there are different active species present. Therefore, electron paramagnetic resonance (EPR) measurements were used to identify the active species in the Co 3 O 4 /PMS and CoS/PMS systems and to evaluate the PMS activation mechanism for subsequent contaminant degradation.…”

Mn-Enhanced Cobalt Silicate-Activated Peroxymonosulfate for Tetracycline Degradation: Inheriting Merit and Offsetting Deficiency of Oxygen Vacancies

“…In recent years, water pollution that arises from the overuse of antibiotics has still been urgently in need of remediation . As one of the most widely used antibiotics, tetracycline (TC) has the characteristics of strong hydrophilicity and a stable structure .…”

“…To enhance the catalytic performance of materials, heteroatom doping has been widely adopted by researchers. , Mn is frequently introduced as a second metal into catalytic systems due to its environmentally friendly and variable valence state . Huang et al clarified that Mn is the active site for catalytic PMS, while Fe­(III) was found to act as the main adsorption site for PMS .…”

“…In recent years, water pollution that arises from the overuse of antibiotics has still been urgently in need of remediation. 1 As one of the most widely used antibiotics, tetracycline (TC) has the characteristics of strong hydrophilicity and a stable structure. 2 To effectively remove such refractory organic pollutants from water, an advanced oxidation process based on peroxymonosulfate (PMS) (SR-AOP) was developed.…”