Selective separation of cadmium from cobalt, copper, iron (III) and zinc by water-based two-phase system of tetrabutylammonium bromide

An aqueous two-phase system of tetrabutylammonim. bromide (TBAB) and (NH 4) 2SO 4mixture is proposed for the selective extraction of trace Cd 2+ from large amounts of Co 2+, Cu 2+, Fe 3+ and Zn 2+. Transparent two-phase system is prepared by mixing 3 ml of 1.0 mol/l TBAB, and 2 ml of sample solution and 1.1g of (NH 4) 2SO 4, the two-phase system thus obtained is of 1.5 ml upper phase and 4.1 ml bottom phase. TBAB was distributed between the upper and bottom phases respectively, but the concentration in upper phase is much higher than that of the bottom phase. The results showed that Cd 2+ is selectively extracted into the upper phase in the pH ranges 1.0–9.0, while Co 2+ Cu 2+ and Fe 3+ ions were little extracted (