Complexing and acid-base properties of silica gels modified with oligoethyleneamines

Acid-base and complexing properties of adsorbents on the basis of silica gel modified with propylamine, ethylenediamine, diethylenetriamine, and tetraethylenepentamine (1) were systematically studied. Conditions for the adsorption of Cu(2), Ni(2), Co(2), Cd(2), Zn(2), Mn(2) and Fe(2) from aqueous solutions were studied. It was demonstrated that these metals, except for Mn(2), are quantitatively extracted from solutions at pH 6-7 and reversibly desorbed with decreasing pH. All the studied metal ions are quantitatively desorbed at pH below 3. On the strength of its properties, 1 is the optimum adsorbent for the separation of transition metals by conventional chromatographic techniques and by chromatofocusing with intercolumn pH gradient. (author)