Measuring and Modeling Adsorption of PAHs to Carbon Nanotubes Over a Six Order of Magnitude Wide Concentration Range

Abstract

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.

Effect of Operating Conditions on PAHs Emission from a Single H2-O2 PEM Fuel Cell

“…Therefore, the emission of LMW-PAHs was more influenced by flowrate than by the different electrochemical reactions of anode and cathode; additionally, the emission of Nap was more influenced by flowrate than those of the other PAH species. The PAHs in the anode or cathode emission gas should be associated with the desorption of the PAHs adsorbed on the carbon materials of PEMFC during operation, although the graphitic structure of carbon materials might have strong interactions with PAHs through π-π interactions (Kah et al, 2011) and PAHs are relatively easier to adsorb on than to desorb from the surface of carbon blacks (Moninot, 2010).…”

Growth and functionalization of carbon nanotubes on quartz filter for environmental applications

“…In the case of trichloroethylene it was found that carbon nanotubes increase the time constant of the slow desorption mechanism (τ 2 ) ( Figure 4a), which is assumed to be mainly related to π-π interactions between CNTs and the C=C bond present in C 2 HCl 3 [14,17]. Due to the removal of doi: 10.7243/2050-1323-3-2 amorphous carbon after the water plasma treatment, and the corresponding surface area enhancement that provides more space for solute adsorption, the desorption time of the wp-CNTsQF sample increased with respect to that of untreated CNTs (Figure 4a, Table 2).…”

“…The characteristics of CNTs suggest that they have strong interaction with organic molecules through non-covalent forces, hydrogen bonds, π-π interactions in, for instance, polycyclic aromatic hydrocarbons (PAHs) [17], electrostatic forces and van der Waals forces. The main interactions responsible for the adsorptions of organic compounds by CNTs are: hydrophobic effect, π-electron donor−acceptor (π-EDA) bonds and hydrogen bonds [18][19][20].…”

Sorption of organophosphate esters by carbon nanotubes

“…LM, usually applicable to describe monolayer adsorption on homogeneous surfaces, is unsuitable for CNTs because the presence of high-energy sorption sites such as defects, functional groups, and interstitial or groove regions between CNT bundles [22] makes the CNTs' surfaces heterogeneous. FM, an empirical equation, failed to describe the sorption behavior of organic pollutants on CNTs over a wide concentration range [23].…”