Mechanisms for strong adsorption of tetracycline to carbon nanotubes: A comparative study using activated carbon and graphite as adsorbents

Abstract

Significant concerns have been raised over the presence of antibiotics including tetracyclines in aquatic environments. We herein studied single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) as potential effective adsorbents for removal of tetracycline from aqueous solution. In comparison, a nonpolar adsorbate, naphthalene, and two other carbonaceous adsorbents, pulverized activated carbon (AC) and nonporous graphite, were used. The observed adsorbent-to-solution distribution coefficient (Kd, L/kg) of tetracycline was in the order of 10(4)-10(6) L/kg for SWNT, 10(3)-10(4) L/kg for MWNT, 10(3)-10(4) L/kg for AC, and 10(3)-10(5) L/kg for graphite. Upon normalization for adsorbent surface area, the adsorption affinity of tetracycline decreased in the order of graphite/ SWNT > MWNT >> AC. The weaker adsorption of tetracycline to AC indicates that for bulky adsorbates adsorption affinity is greatly affected by the accessibility of available adsorption sites. The remarkably strong adsorption of tetracycline to the carbon nanotubes and to graphite can be attributed to the strong adsorptive interactions (van der Waals forces, pi-pi electron-donor-acceptor interactions, cation-pi bonding) with the graphene surface. Complexation between tetracycline and model graphene compounds (naphthalene, phenanthrene, pyrene) in solution phase was verified by ring current-induced 1H NMR upfield chemical shifts of tetracycline moieties.

Sorption of aromatic hydrocarbons onto montmorillonite as affected by norfloxacin

“…Thus, the ring current-induced upfield chemical shifts of 1 H NMR can serve as a strong evidence for face to face complexation of the probed molecule with aromatic structures. In previous studies, the observed 1 H/ 13 C NMR upfield chemical shifts have been used to support -EDA complexation between -electronacceptor compounds and PAHs (-electron-donors) [32]. In this study, prominent 1 HNM upfield shifts are observed for Nor + in mixtures with PAHs (-electron-donors).…”

Preparation of amino-Fe(III) functionalized mesoporous silica for synergistic adsorption of tetracycline and copper

“…Among these methods, adsorption remains attractive because of its advantages of easy operation, energy savings and high removal capacity. Many adsorbents have been used to adsorb antibiotics or heavy metals from water separately, but fewer were used to remove them together (Figueroa et al, 2004;Ge et al, 2012;Ji et al, 2009;Oh et al, 2007;Sassman and Lee, 2005;Vu et al, 2010;Yang and Jiang, 2014;Hasan et al, 2013). In recent years, the cosorption of antibiotics and heavy metals from water by some adsorbents has been attracting increasing concern due to the realistic demands (Kang et al, 2010;Ling et al, 2013;Wang et al, 2008).…”

Facile synthesis, characterization of a MnFe2O4/activated carbon magnetic composite and its effectiveness in tetracycline removal

“…As a result, residues of TCs discharged from municipal wastewater treatment plants (WWTPs) and agricultural runoff are frequently detected in sewage, agricultural wastewater, surface water, groundwater, and even drinking water [5e7]. Exposures to low-level antibiotics in the environment have raised significant concerns of the toxic effect, as well as the transfer and spread of antibiotic resistant genes among microorganisms [7]. As stated by the World Health Organization, the increasing emergence of antibiotic resistance in human pathogens is a special concern, not only for treating infectious disease, but also for other pathologies in which antibiotic prophylaxis is needed for avoiding associated infections [8].…”