Synthesis of pyridin-3-yl-functionalized silica as a chelating sorbent for solid-phase adsorption of Hg(II), Pb(II), Zn(II), and Cd(II) from water

Silica gel modified with 3-aminopropyltrimethoxysilane was anchored with nicotinaldehyde to prepare a new chelating surface (or matrix). It was synthesized and characterized by elemental analysis, cross-polarization magic-angle spinning ¹³C nuclear magnetic resonance (NMR) spectroscopy, diffuse reflectance infrared Fourier-transform spectroscopy, nitrogen adsorption–desorption isotherm, Brunauer–Emmett–Teller surface area, and Barrett–Joyner–Halenda pore sizes. The new surface exhibits good chemical and thermal stability as determined by thermogravimetry curves. This new organic–inorganic material was used for preconcentration of Hg(II), Pb(II), Zn(II), and Cd(II) from water prior to their determination by inductively coupled plasma atomic emission spectrometry. The optimum pH for quantitative sorption of these metal ions is in the range of 6–8, and the sorption capacity is in range of 486–1,449 μmol/g. By batch method, 95 % extraction takes ≤30 min. All the metals could be desorbed with a solution of hydrochloric acid (6 N) without loss of the expensive ligand. Solutions of the metal ions were prepared by dissolution of the nitrate solution.