Waste solution from the Ni non-electric plating process contains 4.0kg/㎥ Ni (II), 0.1kg/㎥ Fe (III), 0.01kg/㎥ Zn (II), 48kg/㎥ SO₄²⁻, 98kg/㎥ HP0₃²⁻ and 31kg/㎥ lactic acid as a typical composition. Solvent extraction, cementation, ion exchange resin and precipitation methods may be used for the treatment of this kind of solution. In this study, solvent extraction of Ni (II) is investigated using two kinds of extractant in order to clarify the relation between extraction percent age and pH for various extractant mixtures. As Ni ions have an octahedral structure with ligands, the synergistic effect for Ni extraction may be effected by using two types of extractants
