Persulfate Chemical Functionalization of Carbon Nanotubes and Associated Adsorption Behavior in Aqueous Phase

Abstract

The chemical functionalization of carbon nanotubes (CNTs) using sodium persulfate (SPS) oxidation was designed to improve their dispersion stability in water. The test results indicated that base activated SPS oxidation of CNTs (BSPS/CNTs) adds a significant amount of oxygen functional groups to the surface of CNTs. The BSPS/CNTs dispersion is dependent on a solution within the pH range of 5–12. Experimental results obtained by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that CNTs were successfully modified and the carboxylic functional groups (e.g., –COO–Na+ or –COO–H+) were created. The BSPS/CNTs, which carry negative charges, enhance the dispersion characteristics of CNTs. The BSPS/CNTs adsorption capacities of inorganic ions (e.g., copper ion) and organic compounds (e.g., benzene) were higher than those obtained by raw CNTs mainly due to enhanced CNTs dispersion. Furthermore, Langmuir and Freundlich adsorption models were applied to examine both raw CNTs and BSPS/CNTs adsorption behaviors. Copper and benzene sorption onto BSPS/CNTs fit the Freundlich isotherm model well, while raw CNTs adsorption did not fit any model. The findings of this study are of great significance for the base activated persulfate oxidation process, indicating that the functionalization of CNTs enhances CNTs dispersivity in water.