Supported liquid membrane extraction of W(VI) ions using tri-n-octylamine as carrier

Abstract

Study of the extraction of W(VI) ions using supported liquid membrane has been carried out. The carrier used for this metal ion transport, is tri-n-octylamine (TOA) dissolved in xylene. The liquid was supported in microporous polypropylene film. The parameters studied are effect of carrier concentration in the membrane, acid concentrations in the feed solution, concentration of stripping agent on transport of W(VI) ions and of temperature on the transport properties of these supported liquid membranes. The optimum conditions of transport for these metal ions determined are, TOA concentration, 0.66 mol·dm⁻³ (TOA); HF concentration in the feed solution, 0.01 mol·dm⁻³ and concentration of NaOH used as stripping agent 2.5 mol·dm⁻³. The maximum flux and permeability determined under optimum conditions are 3.06·10⁻⁵ mol·m⁻²·s⁻¹ and 8.44·10⁻¹¹ mol· ·m²·s⁻¹ at 25±2°C and 4.21·10⁻⁵ mol·m⁻²·s⁻¹ and 11.55·10⁻¹¹ mol·m²·s⁻¹ at 65°C, respectively. The diffusion coefficients for the metal ion carrier complex in the membrane have also been determined. Under the optimum conditions the value for the metal ion carrier complex is 0.14·10⁻¹¹ mol·m²·s⁻¹. Mechanism of transport and the complex formed in the presence of HF have also been discussed. The transport process involves two carrier amine molecules and two protons.