Adsorption of Polar and Nonpolar Organic Chemicals to Carbon Nanotubes

Abstract

Understanding adsorptive interactions between organic contaminants and carbon nanotubes is critical to both the environmental application of carbon nanotubes as special adsorbents and the assessment of the potential impact of carbon nanotubes on the fate and transport of organic contaminants in the environment. The adsorption of organic compounds with varied physical-chemical properties (hydrophobicity, polarity, electron polarizability, and size) to one single-walled carbon nanotube (SWNT) and two multiwalled carbon nanotubes (MWNTs) was evaluated. For a given carbon nanotube, the adsorption affinity correlated poorly with hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics < nitroaromatics, and within the group of nitroaromatics, the adsorption affinity increased with the number of nitrofunctional groups. We propose that the strong adsorptive interaction between carbon nanotubes and nitroaromatics was due to the π-π electron-donor-acceptor (EDA) interaction between nitroaromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of carbon nanotubes. Additionally, we attribute the stronger adsorption of nonpolar aromatics compared to that of nonpolar aliphatics to the π-electron coupling between the flat surfaces of both aromatic molecules and carbon nanotubes. For tetrachlorobenzene, the bulkiest adsorbate, adsorption affinity (on a unit surface area basis) to the SWNT was much stronger than to the two MWNTs, indicating a probable molecular sieving effect.

Insights into Adsorption of Chlorobenzene in High Silica MFI and FAU Zeolites Gained from Chromatographic and Diffractometric Techniques

“…In recent years, organic contaminants removal by single-walled carbon nanotubes (SWCNTs) has attracted great interest due to their chemical, electronic and mechanical properties [18]. However, the saturation capacity of these adsorbents for OClCs is moderate and functional groups on the surface of carbonaceous adsorbents can further reduce the adsorption features [19][20][21]. In the past few decades, surfactant modified clays have been proposed as a potential alternative to carbonaceous adsorbents for removing OClC pollutants.…”

Adsorption kinetics, isotherms and thermodynamics of atrazine on surface oxidized multiwalled carbon nanotubes

“…The adsorption of organic contaminants on MWCNTs has been studied extensively [14][15][16][17][18][19][20][21][22]. The adsorption of atrazine on MWCNTs was reported by Yan et al [23] and Chen et al [24].…”

“…Investigations dealing with the sorption of organic contaminants, such as dioxin [15], 1,2-dichlorobenzene [16], trihalomethanes [17], PAHs [18] and o-xylene, p-xylene [19] and reactive dyes [20] on CNTs suggest that CNTs may also be suitable candidates for the pre-concentration and solidification of pollutants from large volumes of wastewater. Strong adsorptive interaction between CNTs and polycyclic aromatic hydrocarbons were ascribed to -electron-donor-acceptor (EDA) interactions between aromatic molecules (electron acceptors) and the highly polarizable graphene sheets (electron donors) of CNTs [18,21]. In addition, hydrophobic effect, dispersion and weak dipolar forces as well as micropore diffusion are also considered to be responsible for adsorption [18,19,22].…”

Adsorption of diuron and dichlobenil on multiwalled carbon nanotubes as affected by lead

“…CNTs are considered a superior adsorbent for potential environmental remediation due to their large surface area and high reactivity [16][17][18][19]. The sorption mechanisms of organic chemicals by CNTs include hydrophobic interactions [20][21][22][23], -interaction [24,25], hydrogen bond [26][27][28], electrostatic interactions and Lewis acid-base interaction [26,29]. However, the relative contribution of a given mechanism to the overall sorption is largely unclear, which needs to be further addressed.…”