Sorption of Aqueous Zn[II] and Cd[II] by Multiwall Carbon Nanotubes: The Relative Roles of Oxygen-Containing Functional Groups and Graphenic Carbon

Abstract

Exposure of multiwalled carbon nanotubes (MWCNTs) to oxidizing acids and other oxidants introduces oxygen-containing functional groups such as hydroxyl, carboxyl, and carbonyl groups onto the surface. This research evaluated how changes in oxygen concentration and distribution of oxygen-containing functional groups influenced the sorption of aqueous zinc and cadmium on MWCNTs. Sorption results with natural char, activated carbon, and a suite of MWCNTs (of varying surface oxygen content) were obtained. Results confirmed that surface oxygen enhances the sorption of both Zn[II] and Cd[II] from aqueous solution. Although Zn[II] sorbed more strongly than Cd[II] for all materials studied, surface oxidation had more effect on the sorption of Cd[II] than of Zn[II]. Additional sorption experiments with Zn[II] and 16 MWCNTs of varying surface oxidation level and functional group distribution revealed the relative contributions of different types of surface sites to sorption. Sorption isotherms were fit using a two-site Langmuir adsorption model that incorporated the independent characterization of functional group distribution. Results showed that carboxyl-carbon sites were over 20 times more energetic for zinc sorption than unoxidized carbon (graphenic-carbon) sites, though both site types are important contributors to sorption.

Effects of titanium dioxide nanoparticles on lead bioconcentration and toxicity on thyroid endocrine system and neuronal development in zebrafish larvae

“…Heavy metals and nano-TiO 2 are simultaneously released in the environment; the higher surface area-to-volume ratio of nano-TiO 2 relative to that of traditional TiO 2 particles allows the NPs to absorb heavy metals and modify their toxicity (Pettibone et al, 2008;Cho et al, 2010). Some reports have studied the possible combined effects from the interaction of nano-TiO 2 with other pollutants (Sun et al, 2009;Hu et al, 2011;Fan et al, 2012).…”

Syntheses of Carbon Nanotube-Metal Oxides Composites; Adsorption and Photo-degradation

“…Numerous experimental studies have already been carried out on the adsorption of heavy metals and hazardous organic materials (Li, et al, 2002;Li, et al, 2003;Chen, et al, 2006;Hyung and Kim, 2008;Goering, et al, 2008). For further enhancement the adsorption ability of CNTs, purification and activation or functionalization of CNTs is essential and can be performed via oxidation treatment (Cho, et al, 2010;Shao, et al, 2010). Purification is necessary to remove the impurities, like catalyst particles, soot, amorphous carbon and other forms, which are often found, mixed with CNTs.…”

Carbon Nanotubes: Nanotoxicity Testing and Bioapplications

“…Fullerenes (CNT cages), single-wall nanotubes, and multiwalled CNT nanotubes may show cytotoxicity. On the other hand, these materials were reported as nontoxic and protective against pathologies of acute or chronic neurodegeneration and liver diseases [31][32][33][34][35][36]. Major concerns emerged because CNT produced superoxide anion, lipid peroxidation, and cytotoxicity in plants and animals [37][38][39][40].…”