Amino-functionalized mesoporous MCM-41: an efficient adsorbent for the removal of chromium (III) ions from aqueous solution
Amino-functionalized mesoporous MCM-41 (NH2-MCM-41) has been synthesized and explored as sorbent for removal of trivalent chromium, from aqueous media. The chemical and morphological structures of NH2-MCM-41 were investigated by scanning electron microscopy, energy-dispersive x-ray, and x-ray diffraction techniques. The best performance of NH2-MCM-41 as sorbent for removal of trivalent chromium was observed at optimized conditions: pH 3, adsorbent dose (1 g/L), contact time (2 hrs) and temperature (40 °C). Langmuir isotherm model was best fitted to the experimental data with high value of regression coefficient compared to Freundlich and Temkin models indicating monolayer adsorption of the chromium ions on the surface of NH2-MCM-41 with the maximum Langmuir adsorption capacity of 83.33 mg/g. The adsorption mechanism can be explained by the combined effects of strong chemical interaction of chromium (III) ions with the surface amino group and some un-reacted silicate groups of NH2-MCM-41. Adsorption kinetics was best described by pseudo-second-order kinetics model as compared to pseudo-first-order and followed by both diffusion as well as intra-particle pore diffusion mechanism. Thermodynamic analysis revealed that the adsorption was highly favorable, spontaneous and endothermic in nature which allows application of amino-functionalized MCM-41 as a promising adsorbent for the treatment of industrial effluents and other environmental samples.