Surface functionalization of mesoporous silica with maltodextrin for efficient adsorption of selective heavy metal ions from aqueous solution

Abstract

A simple non-hydrothermal method for the synthesis of maltodextrin functionalized SBA-16 (SBA-16@MD) is reported for selective adsorption of heavy metal ions (HMIs) including Cd2+, Zn2+, and Cu2+ from aqueous solution. The as-synthesized SBA-16@MD is fully characterized by FESEM, EDX, HRTEM, PXRD, solid-state 13C NMR spectrum, TGA, and BET surface area measurement. The HMIs adsorption was investigated for several parameters, for example, HMIs concentration, adsorbent dose, temperature, pH, contact time, and stirring speed. The SBA-16@MD shows high values of adsorption capacity for Cd2+ (575.53 mg/g), Zn2+ (564.67 mg/g), and Cu2+ (509.73 mg/g) respectively, at pH 6. The calculated adsorption data are best fitted with the Langmuir isotherm inferring homogeneous HMIs adsorption on the surface of SBA-16@MD. The kinetic data are consistent with the pseudo-second-order and intraparticle diffusion models. The calculated thermodynamic data reveals that the nature of adsorption is endothermic and spontaneous. The high values of adsorption capacity, SBA-16@MD for Cd2+, Zn2+, and Cu2+ can be explained based on electrostatic interactions and ion exchange taking place between the SBA-16@MD surface and HMIs.