Synergy Between Adsorption and Persulfate Activation for Contaminant Removal by Modified Nanotubes: The Role of Oxygen Functional Group Regulation.
Abstract
The combination of surface adsorption and persulfate activation offers advantages of carbon materials in removing organic contaminants from wastewater. However, the specific surface chemical structures governing both processes and the synergy between them remain poorly understood. Herein, the surface oxygen-containing functional groups of carbon nanotubes were synthesized and tuned to explore such synergistic effects. To this end, we employed an approach that monitors contaminant concentrations in both liquid and solid phases over time in addition to surface structure characterization, analysis of reactive oxygen species, and modeling of the removal process. Results showed that annealing enhanced the adsorption of contaminants with high conjugated π systems via π-π interactions and significantly improved the degradation of electron-rich contaminants such as phenolic compounds. The key process of peroxymonosulfate activation was the generation of surface-bound superoxide radicals (O2 •-) and mobile singlet oxygen (1O2) at the carbonyl sites on the modified carbon nanotubes. The results of the investigation suggested a synergistic removal mechanism in which surface-bound O2 •- can directly attack pre-adsorbed bisphenol A through surface-bound radical pathway, resulting in faster removal efficiency compared to the case without pre-adsorption. This work provided insights into designing high-performance bifunctional materials and their synergistic relationship between adsorption and catalysis.