Increased Adsorption of Sulfamethoxazole on Suspended Carbon Nanotubes by Dissolved Humic Acid

Abstract

Although dissolved organic matter (DOM) could effectively disperse carbon nanotubes (CNTs), sorption characteristics of DOM-suspended CNTs are unclear. In this study, we evaluated the relative contribution to the overall sorption from dissolved humic acid (DHA) coating (decreased sorption) and CNT dispersion (increased sorption). We observed that the sorption coefficients of sulfamethoxazole (SMX) on DHA-suspended CNTs were up to 2 orders of magnitude higher than that on aggregated CNTs. Although the mass percent of suspended CNTs were low (generally less than 1%), their contributions to SMX adsorption were up to 20%. Because DHA and SMX did not interact with each other due to their negative charges, the suspended CNTs may not be completely coated by DHA and they had considerable hydrophobic surface exposed. Importantly, this study provided the first evidence in aqueous phase of the significantly increased surface area of DHA-suspended CNTs relative to the aggregated ones based on (1)H NMR relaxometry measurements. This study emphasizes that in comparison to aggregated CNTs, the suspended ones have amply exposed surface area and thus have greater environmental impacts, such as enhancing the mobility, transport, and possibly exposure of organic contaminants.

Dispersant selection for nanomaterials: Insight into dispersing functionalized carbon nanotubes by small polar aromatic organic molecules

“…Three hypotheses were proposed. (1) Because of dispersion, the available contact area (S) between CNTs and SPAOM will be increased by sorbed SPAOM [33]. Since linear relationship was found between sorbed amount of SPAOMs (q e ) and concentration of H + (Fig.…”

Heteroaggregation of CeO2 and TiO2 engineered nanoparticles in the aqueous phase: Application of turbiscan stability index and fluorescence excitation-emission matrix (EEM) spectra

“…As a result, the interaction of CeO 2 -TiO 2 -HA is less than that of CeO 2 -HA, possibly due to adsorption competition [70]. This suggests that HA occupies some adsorption sites of these ENPs first and thus decreases the availability of "pristine" ENPs surface for further interactions [71]. HA functions as stabilizing agent by binding with nanoparticles and restricting the heteroaggregation [72].…”

Organic contaminants and carbon nanoparticles: sorption mechanisms and impact parameters

“…Also, DOM and surfactants inhibited the adsorption of phenanthrene and naphthalene on CNTs (Hu et al, 2008;. The explanations for decreased adsorption generally were the occupation of adsorption sites of CNPs due to coating by DOM or surfactants, leading to decreased availability of CNP surfaces for adsorption of organic pollutants (Pan et al, 2013). Another result was increased adsorption of organic pollutants on CNPs.…”

“…The contribution of suspended CNPs to the adsorption of organic chemicals has been ignored due to the lower amounts of suspended CNPs. Thus, in our recent study (Pan et al, 2013), we tried to separate the CNTs into suspended and aggregated types. The results indicated that the apparent overall adsorption of SMX was inhibited by DOM, but the sorption coefficients of SMX on DOM-suspended CNTs were up to two orders of magnitude higher than those on aggregated CNTs.…”