SEPARATION OF COBALT AND NICKEL BY LIQUID SURFACTANT MEMBRANES CONTAINING A SYNTHESIZED CATIONIC SURFACTANT

Separation of cobalt(II) and nickel(II) by using a hydroxyoxime extrac tant has been investigated both in liquid-liquid extraction and in a l iquid surfactant membrane (LSM) system. In the liquid-liquid equilibri um extraction studies, hydroxyoximes showed significant extractability for nickel ions, although LIX 84 was found to have exceptional chelat ing affinity for nickel ions. In the LSM system functionalized by hydr oxyoxime, the cobalt ions were efficiently separated from nickel ions as a result of slower permeation of nickel chelates across the emulsio n membrane. More complete cobalt recovery was achieved in the LSMs dos ed with LM 860 than when the same carrier was applied to the liquid-li quid extraction system. Furthermore, cobalt permeation rate was enhanc ed threefold when a quaternary ammonium type of cationic surfactant wa s used as an emulsifier due to carrier interaction with surfactant at the reaction interface. The permeation mechanism of ions in LSMs was e lucidated by an interfacial reaction model which took into account the adsorption of the carrier and surfactant at the reaction interface.