Thioglycolic acid was immobilized covalently onto silica gel surface by using 3-chloropropyltrimetoxysilane (CPTS) as precursor silylating agent to yield silica 3- propylthioacetic acid (≡Sil-SO₂). The amount of thioglycolic acid immobilized was 0.90 mmol per gram of silica. This new surface displayed a chelating moiety containing sulphur and oxygen basic centres, which are potentially capable of extracting cations from aqueous solution, such as MCl₂ (M = Cu, Ni, Co, Zn). This process of extraction was carried out by the batch method when similar chemisorption isotherms were observed for all cations. The data were adjusted to a modified Langmuir equation. The sequence of the maximum retention capacity was Cu = Ni > Zn > Co. The adsorption generated metal: ligand ratios of 1 : 1 for cations Cu, Ni and Zn, and of 1: 1.5 for Co. The  standard molar enthalpy concerning the formation of modified silica complexes of divalent Cu, Ni, Zn, and Co, as measured by reaction-solution calorimetry in water, at 25 ± 0.001 °C, gave values of 0.56 ± 0.01, 2.56 ± 0.02, 2.7 ± 0.04, and -6.40 ± 0.15 kJmol^-1, respectively.