Functionalization of SBA-15 mesoporous silica with bis-schiff base for the selective removal of Pb(II) from water

Abstract

The SBA-15 type mesoporous silica functionalized by the bis-Schiff base was designed and prepared through three surface modification steps. The obtained nanohybrid, MS-AP, was systematically characterized by a series of analytical techniques, and these thereby confirmed that the bis-Schiff ligand was successfully immobilized and the hexagonal pore structure of SBA-15 was well kept after the modification. Once modified, adsorption tests for Pb(II) were carried out in a bath under various conditions. Kinetic analyses demonstrated that adsorption kinetic was better represented by the pseudo-second-order model and besides this, the adsorption isotherms were well-fitted to the Freundlich model. Under optimal conditions, the theoretical maximum amount of Pb(II) that could be adsorbed by the MS-AP was measured to be 151.5 ​mg ​g−1, which suggested an excellent ions removal performance by the adsorbent. The thermodynamic study confirmed the spontaneous and endothermic nature of Pb(II) sorption with enhanced randomness. In the binary or the multiple mixed ions solutions, the MS-AP exhibited enhanced selectivity for Pb(II) with respect to Cu(II), Cd(II), Mn(II), Mg(II), Co(II) and Ni(II), when compared with the commonly used amine-grafted SBA-15. Furthermore, the ionic strength of the solution had no significant inhibition effect on Pb(II) sorption. Considering the good regeneration ability and reusability of the adsorbent, MS-AP could be promising for the selective removal of Pb(II) from water.