Browsing by Author "Biswas, R. K."

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    Some Physico-Chemical Properties of Cyanex 272 and Extraction of Some Metal Ions
    (University of Rajshahi, 2006-05) Singha, Hari Prosad; Biswas, R. K.
    Using a reported technique for purifying organophosphorous extractants, the as-received Cyanex 272 extractant containing 85% bis-2,4,4-trimethylpentyl- phosphinic acid [BTMPPA] has been purified to a purity of about 99% BTMPPA. The purified reagent has been characterized and compared to the literature values. A technique for the colorimetric estimation of purified Cyanex 272 has been developed. It consists of the digestion of pure sample or its aqueous solution (after evaporating out most of water) with concentrated HNO3 (70%) - HCIO (70%) mixture at 2:1 ratio for 1 h. The oxidizing mixed acid quantitatively converts Cyanex 272 to a clear solution of orthophosphate which can be easily estimated by the molybdenum blue colorimetric method at 830 nm. The method is sensitive with a molar extinction coefficient of 2.6 x 10 and reproducible within ± 2%. Applying this technique of analysis, the dimerization constant (K2), distribution or partition coefficient (K) and the ionization constant (K) of the purified Cyanex 272 ie. BTMPPA have been estimated to be 190, 53 and 5.52 x 10, respectively. Interactions of BTMPPA+ diluent (n-hexane cyclohexane / benzene / toluene / chloroform / carbon tetrachloride / 1,2-dichloroethane (DCE) / 1-heptanol) binary mixtures have been studied in terms of density and viscosity measurements and also in terms of derived properties such as excess molar volumes (V), excess viscosities (n) and excess Gibbs free energy changes of activation of flow (AGE). Variations of these values together with the variations of the Grunberg-Nissan interaction parameter (d) for BTMPPA diluent binary systems show that BTMPPA interacts with the diluents in varying degrees. However, no correlation between d, AGE, nor V and the Cu2+/ Fe3+ - extraction characteristics with BTMPPA could be noticed. - The interfacial adsorption property of Cyanex 272 (purified) at the 0.50 mol/dm3 H2SO4 (pH = 0.8) / BTMPPA - diluent (carbon tetrachloride / cyclohexane/ DCE/ n-hexane / toluene / kerosene / benzene / chloroform / 1-heptanol/ 1-hexanol) interface have been investigated. Applying the Gibbs adsorption isotherm to the y vs. log [BTMPPA] plots for each of the diluent used (y being the interfacial tension, mN/m), the apparent cross-sectional areas (A in A2) of BTMPPA molecules adsorbed at the interfaces have been estimated. A (A3) is found to vary in the order: CCl4 (157 A2)