Analysis of Interfacial Adsorption Equilibrium and Reaction Rate of Phosphorous Acid with Tri-n-octylamine in Toluene

概要

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In order to clarify the extraction mechanism of phosphorous acid with tri-n-octylamine from a spent electroless nickel-plating bath, the interfacial adsorption equilibrium of the chemical species relating to the extraction and the interfacial reaction rate of phosphorous acid in the aqueous solution with tri-n-octylamine in toluene was investigated at 303K. The interfacial tensions between the aqueous and organic phases, containing various concentrations of phosphorous acid and TOA, were measured and analyzed by the Langmuir and Gibbﾕs adsorption isotherms. The interfacial adsorption constants and the interfacial area occupied by TOA and its complex with phosphorous acid were determined. The initial extraction rate of phosphorous acid with TOA in toluene was measured using a Lewis-type transfer cell. The experimental results were analyzed based on an interfacial reaction model in which the reaction proceeds by successive reactions between TOA and the extraction complexes adsorbed at the interface and the undissociated phosphorous acid in the aqueous solution. The extraction rate in the initial stage of the extraction is interpreted by the rate equation in which the release step of the A'B complex species from the interface is the rate-determining step. The reaction rate constant and the equilibrium constant for the each reaction step were determined.
Japanese Association of Solvent Extraction,日本溶媒抽出学会の論文