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

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.

[Synergistic Enhancement on Oxidation of Phenol by Fenton Processes by Adding Ce3+ and Cu2+ Ions].

Synergistic effect of Ce3+ and Cu2+ on the oxidation efficiency of phenol in different initial pH and H2O2 concentrations by Fenton processes was studied. The experiment results illustrated that Ce3+/Cu2+/Fe2+/H2O2 system had a wider scope of application than Fenton process in the aspect of pH and H2O2 concentration. Phenol was still efficiently degraded by Ce3+/Cu2+/Fe2+/H2O2 at a higher pH (pH=5.0) and a higher H2O2 concentration (2.0 mmol·L-1). In addition, Cu2+ could react with quinone-like substrates, the oxidation intermediates of phenol, to produce Cu+, which could catalyze the decomposition of H2O2 to form·OH, while Ce3+ could accelerate the formation of quinone-like substrates and facilitate the cycling of Fe3+ and Fe2+, to enhance the decomposition of H2O2 to form·OH, the mechanism analysis illuminated the synergy of Ce3+ and Cu2+. The reactive species in Ce3+/Cu2+/Fe2+/H2O2 system was still proved to be·OH, resulting from the scavenging experiments by adding different radical scavengers.