Competitive Adsorption of Polycyclic Aromatic Hydrocarbons to Carbon Nanotubes and the Impact on Bioavailability to Fathead Minnow (Pimephales promelas)

Abstract

Recent studies investigating the influence of carbon nanotubes (CNTs) on the bioavailability of organic contaminants have mostly focused on single‐solute systems; however, a more likely scenario in the natural environment is a multisolute system where chemical interactions at the surface of the CNT may alter the bioavailability of these chemicals. In the present study bisolute adsorption isotherms of pairs of chemically similar polycyclic aromatic hydrocarbons (PAHs) by multiwalled carbon nanotubes (MWCNTs) were established, in conjunction with quantifying the bioavailability of the 2 competing MWCNT‐adsorbed PAHs to Pimephales promelas using bile analysis by high‐performance liquid chromatography with fluorescence detection. The results showed that whereas adsorption and bioavailability of chemically similar PAHs (anthracene and phenanthrene, and fluoranthene and pyrene) were the same in a single‐solute system, in bisolute systems, PAHs that could better align or flex with the MWCNT surface due to morphological characteristics would outcompete the more rigid or planar PAHs. The bioavailability of individual PAHs in bisolute solutions increased by as much as 50% compared with single‐solute solutions. However, the relationship between adsorption (i.e., Kd) and concentration of PAH in the fish bile was similar in single and bisolute systems. This finding indicates that competitive interactions at the surface of MWCNTs influence bioavailability by way of altering adsorption affinity in a moderately predictable manner. Environ Toxicol Chem 2020;39:1702–1711. © 2020 SETAC

Single and Competitive Adsorption of Naphthalene, Phenanthrene, and Pyrene on Polystyrene Nanofibers

“…Solid adsorption materials are widely used to remove PAHs from aquatic environments due to their low cost and high removal efficiency . Currently, natural minerals and carbon materials such as carbon nanotubes and multiwalled carbon nanotubes are often used to remove pollutants from the water environment, but their use is limited by their high cost. − …”

“…Although the adsorption of PAHs with similar physicochemical properties is similar in a single system, the molecular structure of the compounds is also a factor affecting adsorption in a multisolve system. Linard et al found that although chemically similar PAHs (anthracene and phenanthrene, as well as fluoranthene and pyrene) were adsorbed identically in the single system, PAHs that were better aligned or bent to the multiwalled carbon nanotubes (MWCNTs) surface will have an adsorption advantage in the biosolvate system. − The single system and multisystem adsorption mechanisms of PAHs by carbon nanotubes (CNTs) were described by Yang et al, using Polanyi’s theory. In their study, they found that the available adsorption sites for CNTs were cylindrical outer surfaces rather than internal cavities or interwall spaces, and surface adsorption was the dominant mechanism for the adsorption of PAHs in a single or multisystem …”

Linear adsorption of organic compounds on mesoporous activated carbon in bi-solute system

“…It was verified in our studies by the nonlinear and high sorption of organic compounds to a resin ADS-12, humus-like substances humificated from rice straw, and organobentonites, respectively, all of which were with undetectable surface area [ 17 , [20] , [21] , [22] ]. The linear adsorption mechanism was also proposed and used to interpret the linear sorption of organic compounds to carbon nanotubes (CNTs) under the competitive sorption of coexisted solutes [ 16 , 23 ]. However, CNTs were not an ideal adsorbent for verifying the linear adsorption mechanism, because CNTs were reported to contain a certain amount of carbonaceous impurities and mobile graphene layers, which could behave like a linear partition phase for organic compounds [ [24] , [25] , [26] , [27] ].…”