Facile synthesis of alumina-decorated multi-walled carbon nanotubes for simultaneous adsorption of cadmium ion and trichloroethylene

Abstract

An adsorbent was prepared by decorating alumina onto the surface of multi-wall carbon nanotubes (MWCNTs) for simultaneous removal of cadmium ion (Cd(II) ion) and trichloroethylene (TCE) from groundwater. Structural characterization demonstrated that the nanocomposites was successfully synthesized and exhibited large surface area and restrained aggregation property. Batch experiments were conducted under various conditions (i.e., different pH, the presence of other groundwater constituents) to investigate the removal of Cd(II) ion or/and TCE by the alumina-decorated multi-walled carbon nanotubes (Al2O3/MWCNTs) and the underlying mechanisms. The adsorption kinetics of Cd(II) ion and TCE followed the pseudo-second-order kinetic model and exhibited 3-stage intraparticle diffusion mode. Equilibrium data of Cd(II) ion and TCE were best fitted by Langmuir and Freundlich model, respectively. The adsorption mechanisms of Al2O3/MWCNTs toward Cd(II) ion and TCE mainly involved in the electrostatic interactions, the hydrogen bond interactions and the protonation or hydroxylation of Al2O3. The maximum adsorption capacities of Al2O3/MWCNTs for TCE and Cd(II) ion were 19.84mg/g and 27.21mg/g, respectively, which were higher than that of Al2O3, MWCNTs and the functionalized MWCNTs. The results suggested that the Al2O3/MWCNTs could be considered as an effective and promising adsorbent for simultaneous removal of Cd(II) ion and TCE from groundwater.