Adsorption and separation of cations on chemically modified silica gel synthesised via the sol–gel process

Abstract

The reaction of ethylene sulfide [(H₂C)₂S] with 3-aminopropyltrimethoxysilane resulted in a new silylating agent, which was anchored onto a silica surface via the sol–gel procedure. The synthesised silica gel surface has been used to adsorb divalent cations from aqueous solutions at room temperature. The series of isotherms of adsorption were adjusted to a modified Langmuir equation from data obtained by suspending the solid in water with MCl₂ (M = Cu, Ni, Co, Pb and Hg) solutions, which gave the maximum number of moles adsorbed as 1.66, 1.44, 1.26, 1.90 and 8.51 mmol g⁻¹, respectively. The immobilised surface was also used for the separation of these five cations in a column. Column resolution, R_(s), was determined for all cations as the ability of the surface to separate metal ions, determined as R_(s)Co–Ni = 0.20, R_(s)Co–Cu = 0.73, R_(s)Co–Pb = 2.50, R_(s)Co–Hg = 1.73, R_(s)Ni–Cu = 0.55, R_(s)Ni–Pb = 2.25, R_(s)Ni–Hg = 1.69, R_(s)Cu–Pb = 1.33, R_(s)Cu–Hg = 1.52 and R_(s)Pb–Hg = 1.35.