On Cadmium (II) Membrane-Based Extraction using Cyanex 923 as Carrier

ISSN： 0736-6299

Source： Solvent Extraction and Ion Exchange, Vol.26, Iss.3, 2008-05, pp. : 192-207

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Abstract

The facilitated transport of cadmium (II) from HCl medium by Emulsion Pertraction Technique (EPERT), using Cyanex 923 (phosphine oxides mixture) as ionophore, is investigated as a function of various experimental variables: hydrodynamic conditions, concentration of cadmium (II) (5-100 mg L-1) and HCl (0.2-5 M) in the source phase, carrier concentration (5-40% v/v) and diluent in the organic phase. A model that describes the transport mechanism is derived, consisting of diffusion through a source aqueous diffusion layer, a fast interfacial chemical reaction, and diffusion of the carrier and the metal complexes through the membrane. The thickness of the source phase boundary layer was calculated as 2.2×10-3 cm. The organic membrane diffusional resistance (Δorg) and aqueous diffusional resistance (Δaq) were calculated from the model, and their values were 1.0×107 s cm-1 and 347 s cm-1, respectively, whereas the values of the bulk diffusion coefficient (Dorg,b) and diffusion coefficient (Dorg) also calculated from the model were 4.8×10-9 cm2 s-1 and 1.3×10-9 cm2 s-1. The separation of Cd(II) against Zn(II), Fe(III), Cr(VI) and Cu(II) and also the performance of the system in relation with other extractants were evaluated.