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))(2)SO(4)mixture 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))(2)SO(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 (<1%) at pH 3.0. Zinc ion was extracted to upper phase by about 24%, but it did not interfere the extraction of Cd(2+). The interaction between CdBr(4)(2-) and TBA(+) plays an important role in the extraction process.