Thermodynamic and Kinetic Behaviors of Persulfate-Based Electron-Transfer Regime in Carbocatalysis

This study reveals the thermodynamic and kinetic behaviorsof the electron-transfer pathway for the selective oxidation of organiccontaminants. A carbon-based advanced oxidation process is featuredfor the nonradicalelectron-transfer pathway (ETP) from electron-donating organic compoundsto activated persulfate complexes, enabling it as a green technologyfor the selective oxidation of organic pollutants in complex waterenvironments. However, the thermodynamic and kinetic behaviors ofthe nonradical electron-transfer regime had been ambiguous due toa neglect of the influence of pH on the mechanisms. In this study,three kinds of organic pollutants were divided in the carbon-basedETP regime: (i) physio-adsorption, (ii) adsorption-dominated ETP (oxidationrate slightly surpasses adsorption rate), and (iii) oxidation-dominatedETP (oxidation rate outpaces the adsorption rate). The differentialkinetic behaviors were attributed to the physicochemical propertiesof the organic pollutants. For example, the hydrophobicity, molecularradius, and positive electrostatic potential controlled the mass-transferprocess of the adsorption stage of the reactants (peroxydisulfate(PDS) and organics). Meanwhile, other descriptors, including the Fukuiindex, oxidation potential, and electron cloud density regulated theelectron-transfer processes and thus the kinetics of oxidation. Mostimportantly, the oxidation pathways of these organic pollutants couldbe altered by adjusting the water chemistry. This study reveals theprinciples for developing efficient nonradical systems to selectivelyremove and recycle organic pollutants in wastewater.