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KMID : 1059519920360040540
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Journal of the Korean Chemical Society
1992 Volume.36 No. 4 p.540 ~ p.545
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A Study on the Solvent Extraction Kinetics of Complex Nickel(Ⅱ) 8-Hydroxyquinolinate by Spectrophotometry
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Lee Heung-Lark
Oh In-Gyung
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Abstract
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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 × KHOx / KD,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.
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KEYWORD
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