Interactions Between Carbon Nanotubes And Organic Compounds By Chromatographic Method

The unique structures of carbon nanotubes (CNTs) allow strong interactions with organic pollutants, which could affect the transport and fate of both adsorbed organic pollutants and CNTs in the environment. The understanding of the interactions between toxic organic pollutants and CNTs is critical for their environmental fate assessment. For most of studies, the interactions between organic compounds and CNTs were investigated by the batch equilibration experiments and the passive dosing method. However, the traditional batch equilibration technique had some shortcomings such as complicated steps and time-consuming and were not efficient to separate CNTs from the liquid phase. The passive dosing method is not involved separation procedure in traditional batch equilibration experiments, but it is complicated and requires long equilibrium time. Therefore, an analytical method, which is fast, efficient and effectively solves the separation between the stationary phase and the liquid phase, is needed. In this work, CNTs were used as the stationary phase, while CNTs columns were packed by the downward slurry method. We attempted to develop a method by combining the self-packing CNTs column with HPLC for investigating the interactions between organic compounds and MWCNTs.(1) The retention factors (k’) of9organic compounds on the multi-walled carbon nanotubes (MWCNTs) column at different temperatures were measured. Thermodynamics parameters of organic compounds on MWCNTs column were calculated by the Van’t Hoff equation. The results indicated that the interactions between MWCNTs and organic compounds were spontaneous and exothermic. Based on the analysis of k’of9organic compounds on MWCNTs columns, the strength of interactions between MWCNTs and organic compounds was related to types of functional groups. The linear solvation energy relationships (LSER) were adopted to develop the relationship between k’and solvatochromic parameters. The results show that the π-/n-electrons interaction dominated the interactions.(2) k’ of18organic compounds on the single-walled carbon nanotubes (SWCNTs) column were measured. The strength of the interactions between SWCNTs and organic compounds were related to the number and types of functional groups and the number of hetero-atoms. The interactions between SWCNTs and organic compounds were characterized quantitatively by LSER. The obtained LSER model had a goodness of fit (R2=0.844) and robustness (Q2LOO=0.768). The results demonstrated that the π-/n-electrons interactions and the cavity interactions were the main interactions that influence the interactions between SWCNTs and organic compounds.(3) k’of organic compounds on the MWCNTs column in the different mobile composition of water and acetonitrile were measured, k’of organic compounds in pure water were calculated by the Snyder-Soczewinshi equation. The results indicated that the strength of interactions between organic compounds and MWCNTs increased in an order:toluene> benzene> aniline> phenol.(4) The adsorption of sulfonamide antibiotics on MWCNTs were investigated by the adsorption isotherms, which were measured by the frontal analysis method. The results indicated that both Linear and Freundlich models fit the adsorption isotherms well. Adsorption affinities to MWCNTs increased as sulfadimidine> sulfamethoxazole> sulfadiazine.