Thermodynamic study on aniline adsorption on chemical modified multi-walled carbon nanotubes

The thermodynamic behaviors of aniline adsorption on the surface of chemical modified carbon nanotubes (CNTs) are studied, which indicate to understand their surface chemical characteristics. Pristine CNTs were treated by citric acid, potassium permanganate and nitric acid to obtain the modified samples. TEM and FT-IR spectrometry are employed to characterize the surface physics and chemistry of the treated CNTs. Aniline adsorptive capacities of the samples are evaluated at different temperatures by measuring the UV–vis absorption of aniline. Both Langmuir and Freundlich models are introduced to fit the adsorption isotherms data, and thermodynamic constants (K0, ΔG, ΔH and ΔS) are calculated to evaluate the orientation and feasibility of the physicochemical adsorptive reactions. Results show that the CNTs treated by citric acid possess favorable performance for aniline adsorption at high temperature. In addition, the corresponding mechanism of interactions between citric acid and CNTs has been proposed and illustrated in the paper.