Facilitated transport of cadmium as anionic iodo-complexes through bulk liquid membrane containing hexadecyltrimethylammonium bromide

The transport of cadmium ions from iodide solutions across a bulk liquid membrane by using hexadecyltrimethylammonium bromide (HDTBr) as carrier dissolved in dichloromethane has been studied at 22 °C. The effect of the fundamental parameters influencing the transport process, e.g. iodide concentration in the feed phase, carrier concentration and type of organic diluent used in the membrane, type and concentration of stripping reagent in the receiving phase, and time dependency of the process has been investigated and discussed. The transported amount of cadmium ions (initial concentration 1 × 10−5 M) from a 0.01 M potassium iodide solution (pH 7) across a dichloromethane solution of HDTBr (1 × 10−3 M) into the receiving phase (H2SO4, 0.05 M) was found to be 96.3 (±0.4)% after 6 h. The selectivity and efficiency of the proposed method were evaluated by performing the competitive transport experiments on the mixtures containing Cd2+, Ni2+, Co2+, Zn2+, Cu2+ and Pb2+ ions. The applicability of the method for recovering the cadmium ions from a solution obtained by acid leaching of spent rechargeable Ni–Cd batteries was examined.