Influence of precursors on synthesis and metal sorption properties of Schiff's base doped Silica

Abstract

To investigate the influence of silica precursor on the synthesis and metal sorption properties of Schiff’s base doped mesoporous silica. Different silica precursors including TEOS, calcined mesoporous silica, silica gel 60, VTES, PTMS and ETES were used. Various Schiff’s bases namely, salen, saltn and haen were used as doping molecules. The Schiff’s base doped mesoporous silica synthesized from TEOS, calcined mesoporous silica, VTES, PTMS, and ETES had large surface area, narrow pore size distribution, crystalline structure, and spherical shape. The extraction properties of the modified silica towards Cu(II), Fe(III) and Ni(II) were determined. The influence of the ratio of Schiff’s base/TEOS on the synthesis and extraction properties were investigated. The maximum amounts of incorporating Schiff’s base were found to be 1.00, 0.86, and 0.96 mmol g [superscript -1] for salen, saltn, and haen doped mesoporous silica, respectively. The extraction of Fe(III) was increased with the increase of amount of incorporated Schiff’s base. The profound extraction studies were performed on the salen doped mesoporous silica synthesized from TEOS or calcined mesoporous silica due to their excellent physical and chemical properties. Adsorption kinetic of these sorbents was consistent with the pseudo-second order model. The adsorption isotherm was best fitted to the Langmuir model. The Cu(II) and Fe(III) maximum extraction capacity of salen doped mesoporous silica synthesized from calcined mesoporous silica was found to be 18.42 and 20.70 mg g-1 respectively. The reusability of the modified silica was also assessed for three successive adsorption-desorption cycles.