ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 36, Number 4
JKCSEZ 36(4)
August 20, 1992 

Kinetics and mechanism on the solvent extraction of nickel(Ⅱ) with 8-hydroxyquinoline (HOx) was studied spectrophotometrically. Absorbance variation was measured by changing the 8-hydroxyquinoline concentration in the chloroform organic phase and the pH values in the aquous phase. By analyzing absorbance data the reaction rate was found to be the first order for 8-hydroxyquinoline concentration and the inverse first one for [H+]. Therefore the rate determining step of the extraction reaction is the formation of the one-to-one metal chelate NiOx+ and the rate equation is as follows; -d[Ni2+]/dt = k[Ni2+][Ox-] = k'[Ni2+][HOx]_o/[H+]. The value of k' was evaluated from the slope of plot of log [Ni2+]_o/[Ni2+]_t versus time and the rate constant k was calculated according to the equation k' = k × K_HOx / K_D,HOx. From the temperature dependence of the extraction rate, the activation energy Ea = 6.26 kcal/mol is calculated, and activation parameters, △G^≠₂₉₈ = 6.59 kcal/mol, △H^≠₂₉₈ = 5.68 kcal/mol, △S^≠₂₉₈ = -3.09 eu/mol are estimated.