Exploring the peroxydisulfate activation by carbon nanotubes for pollutants degradation: Identification of the primary reaction mechanism and key molecular descriptor

Abstract

Carbon nanotubes (CNT) have been proposed to activate persulfate over the past decade, resulting in successful degradation performance for organic pollutants in wastewater treatment. However, there is debate over the reaction mechanism involving radical versus non-radical pathways, setting up a roadblock to further developing persulfate activation by carbonaceous materials. This work focused on the carbon nanotubes/peroxydisulfate (CNT/PDS) system, investigated its reaction mechanism, and unveiled the relationship from the aspect of molecular descriptors. The involvement of radicals (e.g., SO4•− and HO•) and 1O2 was ruled out by the observation of quenching effect, oxidation products, chemical probes, solvent exchange, and electron paramagnetic resonance spectra. Then, mediated electron transfer was deemed as the primary reaction mechanism based on linear sweep voltammetry analysis, which was supported by the PDS consumption result. The substrate-dependent treatment capacity was found in the CNT/PDS for multiple contaminants degradation, and it turned out that EB3LYP was the most significant parameter in the relationship between degradation rates and molecular descriptors. Outstanding environmental application was exhibited based on the coexistence of various organic/inorganic substances and repeated degradation experiment. Therefore, the findings from this study would be helpful for both scientific research and technical development of persulfate activation by CNT.