“…Nickel, as well as copper and palladium, is extracted into the organic phase with hydroxyoximes as a square planar chelate according to the extraction reaction described by Ni2+ +2HR^=± NiR2 +2H+ (4) where the extraction equilibrium constant with HNAPOwas evaluated as Ke=3.2x\0~5 in the previous study. 5) According to the inter facial reaction scheme proposed by Komasawaet al (10) For the description of 6NiR+ as a function of the concentrations of the reactant species, three kinds of species should be taken into consideration as the adsorbed species: monomeric HNAPO, the intermediate complex and the final chelate.…”