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Title: Solvent extraction of Cu(II) by purified cyanex 272
Authors: Biswas, R K
Singha, H P
Keywords: Liquid-liquid extraction
Sulphate medium
Cyanex 272
Issue Date: May-2007
Publisher: CSIR
Series/Report no.: B01D11/00, C22B3/26
Abstract: The solvent extraction of Cu(II) from 0.10 mol/dm³ sulphate medium by purified cyanex 272 (bis-2,4,4-trimethylpentylphosphinic acid, BTMPPA, H₂A₂) dissolved in distilled aliphatic kerosene has been investigated. The equilibration time is less than 15 min. The distribution ratio is found to decrease appreciably with equilibrium Cu(II) concentration in the aqueous phase, particularly, at its higher concentration region indicating some sort of association of Cu(II) species in either of the phases. The pH and the extractant concentration dependences on distribution ratio are 1 and 1.2, respectively. The distribution ratio is almost independent of sulphate ion concentration in the aqueous phase. The ΔH value is 27.3 ± 0.5 kJ/mol. The 60% extraction equilibrium reaction is suggested to be: CuHSO₄⁺ + H₂A₂₍₀₎ ⁀ CuHSO₄ A. 0.5 H₂A₂₍₀₎ + H⁺ and some 40% extraction is likely to occur via the reaction, CuHSO₄⁺ + 1.5 H₂A₂₍₀₎ ⁀ CuHSO₄A.H₂A₂₍₀₎ + H⁺ satisfying the extractant dependence of 1.20. The apparent extraction equilibrium constant (Kex) is estimated to be 10⁻³˙¹⁵. The loading capacity of BTMPPA is 13.47 g Cu(II)/100 g BTMPPA. Among H₂SO₄, HCl and HNO³ solutions as stripping agent, 1 mol/dm³ H₂SO₄ solution is found to be the best; 99.6% Cu(II) in the organic phase can be stripped off in three stages (O/A = 1 in each stage). The Cu(II) distribution ratio measured at pH = 4 in different diluents does not show good correlation with the cross-sectional area of BTMPPA molecules at interfaces formed by different diluents at pH 0.80.
Description: 269-275
ISSN: 0971–457X
Appears in Collections:IJCT Vol.14(3) [May 2007]

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