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

Abstract

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 ( G), standard enthalpy ( H), and standard entropy changes ( S) were measured. The values of H and 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.

Carbon nanotubes as adsorbents in environmental pollution management: A review

“…CNTs have shown exceptional adsorption capability and high adsorption efficiency for various organic contaminants such as dioxin [17], benzene [173,174], 1,2-dichlorobenzene [71,175], trihalomethanes [94,176] and polycyclic aromatic hydrocarbons (PAHs) [177]. Aromatic compounds have relatively higher adsorption affinity to CNTs than no aromatics.…”

Adsorption Characteristics of Atrazine on Granulated Activated Carbon and Carbon Nanotubes

“…The PMM theory involves a pore filling mechanism and the concept of a variable adsorption potential in response to pore filling. According to this theory, initially, CNT forms bundles in aqueous solution and the spaces between the tubes within the bundles can be regarded as pores [35]. It can also be noticed that the PMM parameter Q 0 (maximum adsorption volume capacity, not shown) decreased with temperature, indicating that the standard enthalpy associated with the adsorption of ATZ on CNT is negative.…”

Organic contaminants and carbon nanoparticles: sorption mechanisms and impact parameters

“…The altered adsorption of organic contaminants on CNPs as affected by oxidation results from two characteristics. First, oxidized CNPs are more hydrophilic than pristine CNPs because the surface wettability of CNPs is enhanced by oxygencontaining functional groups, leading to increased adsorption of hydrophilic contaminants and decreased adsorption of hydrophobic contaminants Cho et al, 2008;Shen et al, 2009). Second, the functional groups of CNPs can interact with water through hydrogen bonding, leading to the formation of water clusters, which decrease the accessibility of CNP surfaces to organic contaminants (Yang et al, 2004).…”