Removal of cadmium from aqueous solutions by oxidized and ethylenediamine-functionalized multi-walled carbon nanotubes

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2010-02, Vol.157 (1), p.238-248
• Main Authors: Vukovic, Goran D, Marinkovic, Aleksandar D, Colic, Miodrag, Ristic, Mirjana D, Aleksic, Radoslav, Peric-Grujic, Aleksandra A, Uskokovic, Petar S
• Format: Article
• Language: English
• Subjects: Adsorption; Amino-functionalization; Applied sciences; Cadmium adsorption; Carbon nanotubes; Chemical engineering; Cytotoxicity; Exact sciences and technology
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2009.11.026

Surface functionalization of multi-walled carbon nanotubes (MWCNTs) by ethylenediamine, via chemical modification of carboxyl groups, using O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate, was performed. The resulting materials were characterized by different techniques, such as FTIR, TGA and elemental analysis. Biocompatibility studies showed that the functionalized MWCNTs, at concentrations between 1 and 50 μg mL −1, were not cytotoxic for the fibroblast L929 cell line. In batch tests, the influences of solution pH, contact time, initial metal ion concentration and temperature on the sorption of Cd 2+ ions onto raw-MWCNTs (raw-MWCNT), oxidized MWCNTs (o-MWCNT) and ethylenediamine-functionalized MWCNTs (e-MWCNT) were studied. The adsorption of Cd 2+ ions by o-MWCNT and e-MWCNT was strongly pH dependent. The time dependent Cd 2+ sorption onto raw-MWCNT, o-MWCNT and e-MWCNT can be described by a pseudo-second-order kinetic model. The Langmuir isotherm model agrees well with the equilibrium experimental data. The maximum capacity was obtained for e-MWCNT, 25.7 mg g −1, at 45 °C. The thermodynamic parameters were also deduced for the adsorption of Cd 2+ ions on raw-MWCNT, o-MWCNT and e-MWCNT and the results showed that the adsorption was spontaneous and endothermic.