Silica gel modified with Titan Yellow as a sorbent for separation and preconcentration of trace amounts of heavy metals from alkaline earth or alkali metal salts

Abstract

Sorption of 12 metal ions (Ca, Mg, Al, Cu, FeIII, Ni, Co, Cd, Zn, Pb, HgII and CrIII) on silica gel impregnated with a mixture of Aliquat 336 and Titan Yellow was investigated in the pH range 1–9. All these metals were retained from alkaline, neutral or slightly acidic aqueous solutions except calcium and magnesium, which were retained only from alkaline solutions. All the retained metals can be eluted with dilute solutions of HClO4(>0.05 mol l–1) or HCI (>0.5 mol l–1) without elution of the chelating reagent from the sorbent taking place, which makes possible the use of the same column for a number of sorption–elution processes. The rate of sorption of Cu, Fe, Cr, Al, Zn, Ca and Mg was also studied and it was found that relatively high flow rates (up to 4 ml min–1) could be used for solutions passing through the column. The sorbent was applied to the separation of solutions of analytical-reagent grade sodium, potassium, calcium, magnesium and ammonium chloride, used as supporting electrolytes in anodic stripping voltammetry, from traces of Cu, Pb, Cd and Zn, and for separation of some metal ion mixtures by column extraction chromatography.