Synthesis and characterization of schiff's base doped mesoporous silica and application to solid-phase extraction of metal

Abstract

Four types of Schiff’s base doped mesoporous silica were synthesized using one of the following Schiff base ligand, namely, salen, saltn, salophen and haen as a doping molecule, tetraethoxysilane as a silica precursor and sodium hydroxide as a catalyst. The influence of Schiff’s base/TEOS mole ratios was also considered. The existence of Schiff’s base molecules in the modified silica was detected by FT-IR analysis. The physical properties of these synthesized materials were characterized using X-ray diffraction technique and N₂ sorption measurement. The results suggested that all synthesized silica had good ordered arrangement of mesopore with narrow pore size distribution. These materials had large surface area and pore volume. The SEM studies demonstrated the spherical morphology of all synthesized silicas. The extraction behavior of the modified silica towards Co(II), Cu(II), Fe(II), Fe(III) and Mn(II) were determined. Various parameters including pH, effect of salts present in metal solution, temperature and amount of silica were investigated. Interestingly, all Schiffs base doped mesoporous silica had high selectivity to Cu(II) and Fe(III) extraction. The metal extraction capacity of Schiffs base doped mesoporous silica was found to be in this order: saltn > salen > salophen > haen doped mesoporous silica. Complete elution of both Cu(II) and Fe(III) ions were achieved using 0.1 M HNO₃ as desorption agent.