Kinetics and thermodynamics of sorption of nitroaromatic compounds to as-grown and oxidized multiwalled carbon nanotubes

• Published in: Journal of colloid and interface science 2009-02, Vol.330 (1), p.1-8
• Main Authors: Shen, Xiu-E, Shan, Xiao-Quan, Dong, De-Ming, Hua, Xiu-Yi, Owens, Gary
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Multiwalled carbon nanotubes; Nitric acid oxidization; Nitroaromatic compounds; Porous materials; Sorption kinetics; Sorption thermodynamics; Surface physical chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2008.10.023

The sorption kinetics and thermodynamics of 1,3-dinitrobenzene (DNB), m-nitrotoluene (mNT), p-nitrophenol (pNP), and nitrobenzene (NB) on as-grown and nitric acid-oxidized multiwalled carbon nanotubes (MWCNTs) were investigated. The sorption kinetics was well described by a pseudo-second-order rate model, while both Langmuir and Freundlich models described the sorption isotherms well and the sorption thermodynamic parameters of equilibrium constant ( K 0 ), standard free energy (Δ G), standard enthalpy (Δ H), and standard entropy changes (Δ S) were measured. The values of Δ H and Δ G suggested that the sorption of nitroaromatics (NACs) onto MWCNTs was exothermic and spontaneous. The structure, number, and position of nitro groups of NACs were the main factors affecting the sorption rate and capacity. Treatment of the MWCNTs with nitric acid increased both the surface area and the pore volume and introduced oxygen-containing functional groups to the MWCNTs, which depressed the sorption of NACs onto MWCNTs. Sorption kinetics of DNB, mNT, pNP, and NB onto MWCNTs can be well described by a pseudo-second-order model.