Enhanced Removal of Metal Ions from Water by Novel Composite Magnesia-amended Silica Granules

The potential of a novel sorbent, magnesia-amended silica granules (MAS), for the removal of metal ions from aqueous solution has been examined. MAS, prepared by calcining magnesium chloride-impregnated silicon dioxide at 773 K, exhibited an adsorption capacity towards metal ions that was 15- to 30-times larger than that of silicon dioxide. Batch sorption studies were performed as a function of contact time and pH. X-Ray powder diffraction (XRD), infrared spectral analysis (FT-IR), porosity and surface area measurements were used to characterize the physicochemical properties of MAS. At an initial concentration of 50 mg/l, more than 90% removal of metal ions was achieved within 8 h contact time at a weak acid pH value. Of the kinetic models tested, the pseudo-second-order model gave the best fit to the kinetic data, while the Langmuir isotherm model provided the best fit to the equilibrium adsorption data for metal ions onto MAS. The adsorption processes were endothermic.