Adsorption of Cu2+ on Amino Functionalized Silica Gel with Different Loading

Silica gel (G) and amino functionalized silica gel with three different loading of an aminopropyl group viz. 0.51, 1.01, and 1.45 mmol/g, (GN1, GN2, and GN3) were synthesized, characterized, and used as adsorbents for the adsorption of Cu 2+ ions from aqueous solution. The specific surface area, pore volume, and BJH pore size of silica gel decreased with an increase in the loading of aminopropyl groups. Kinetic of adsorption of Cu 2+ on GN2 followed pseudosecond order. Adsorption isotherms of Cu 2+ on functionalized silica samples were best fit by the Sips model for all the three functionalized silica gels, among the four models used to describe the Cu 2+ adsorption isotherms. The monolayer copper adsorption capacity for the gel GN1 (0.515 mmol Cu 2+ /g) and GN2 (0.55 mmol Cu 2+ /g) were found to be almost similar even when the loading of the amino group increased from 0.51 to 1.01 mmol/g. The NH 2 /Cu mole ratio was found to be around 1 and 2 for GN1 and GN2, respectively. In the case of GN3 (1.45 mmol NH 2 /g), the monolayer capacity was found to be 1.05 mmol Cu 2+ /g with a NH 2 /Cu mole ratio of 1.38. This study indicates that the population density of NH 2 determines the NH 2 /Cu 2+ ratio at saturation of Cu 2+ on the functionalized silica gel and the affinity of the gel for the Cu 2+ .