Competitive Sorption of Pyrene, Phenanthrene, and Naphthalene on Multiwalled Carbon Nanotubes

Abstract

Knowledge of toxic chemical sorption by carbon nanotubes (CNTs) is critical for environmental application of CNTs as superior sorbents and for environmental risk assessment of both CNTs and toxic chemicals. Single-solute sorption results were reported in the literature, however, they cannot be used for predicting pollutant sorption by CNTs in wastewater and natural water systems where multiple organic contaminants are present. In this study, competitive sorption of pyrene, phenanthrene, and naphthalene on a multiwalled CNT material was investigated. All isotherms in single-, bi-, and tri-solute systems were fitted well by the Dubinin-Ashtakhov (DA) model. The isotherm of a given primary solute changed from being significantly nonlinear to nearly linear when competitors were added. The observed competitive sorption depended on the relative equilibrium concentrations of both primary and cosolutes. Significant competition was observed at relatively low concentrations of primary solute and high concentrations of competitors, while competition was much weaker in the case of relatively high concentrations of primary solute and low competitor concentrations. When the relative concentration of primary solute (Ce/Cs) approached 1, competition by other solutes seemed to disappear. Sorption and competition of three polycyclic aromatic hydrocarbons (PAHs) on CNTs could not be explained with either pore-filling or partition-adsorption mechanisms. A Polanyi-based surface adsorption mechanism was proposed to interpret the observed sorption and competition.

Determination of 16 polycyclic aromatic hydrocarbons in environmental water samples by solid-phase extraction using multi-walled carbon nanotubes as adsorbent coupled with gas chromatography–mass spectrometry

“…[ over, the loading amounts, namely herein the dynamic adsorption capacities of MWCNTs, could be calculated for the 16 PAHs between 15.08 and 27.56 mg g −1 . It is rarely reported that pollutant sorption by CNTs in natural water systems where multiple organic contaminants are present [33]. Different adsorption capacities of the multiple PAHs are possibly attributed to their competitive sorption on a MWCNT material [33].…”

Competitive adsorption of phenol and 3-chlorophenol on purified MWCNTs

“…In the case of CNTC over-and underestimation may occur equally, depending on the total concentration of the pollutant and their relative concentration. It is worthwhile to mention that Yang et al [10] applied the Polanyi-based Dubinin-Astakhov theory for the competitive adsorption of PAH molecules on a non-functionalized CNT (similar to CNTC). The adsorption calculated from the individual isotherms always overestimated the experimental data.…”

“…The influence of the other solutes was hardly detected when the concentration of the primary solute was close to its solubility limit. As neither pore-filling nor partition-adsorption mechanism explained the behaviour of these PAHs, a Polanyi-based surface adsorption mechanism was proposed to interpret the observed sorption and competition [10]. It was also found that the adsorption of 2,4-dichlorophenol and 4-chloroaniline either in neutral or ionic form can be supressed by nonpolar naphthalene on multiwalled CNT [8].…”

“…From a practical point of view however, competitive adsorption from binary or multisolute systems is more relevant. Reference works apply one of the following techniques for such investigations: i) the concentration of one of the components is systematically changed while that of the others(s) is kept constant [9][10][11][12]; ii) the initial concentration of the pollutants is varied but their molar ratio is kept constant and [9,[13][14]; iii) the total initial concentration of the pollutants is constant but their molar ratios are varied [15][16]. The advantage of the last method is that it makes possible the comparison of the behaviour of solutes in a wide relative concentration range.…”

Potential of carbon nanomaterials for removal of heavy metals from water

“…Carbon nanotubes (CNTs) have shown exceptional adsorption capability and high adsorption efficiency for various organic pollutants such as benzene [14], 1,2-dichlorobenzene [15], trihalomethanes [16] and polycyclic aromatic hydrocarbons (PAHs) [17]. CNTs were found to be superior sorbents for inorganic pollutants such as fluoride [18], and several divalent metal ions [7,8,[19][20][21][22][23][24][25].…”