Hollow fiber supported liquid membrane for the separation/concentration of gold(I) from aqueous cyanide media: Modeling and mass transfer evaluation

The application of a hollow fiber supported liquid membrane (HFSLM) for the simultaneous recovery and concentration of gold(I) from alkaline cyanide media using microporous hydrophobic polypropylene hollow fiber is considered. In HFSLM configurations, the organic extractant used for gold(I) extraction was 2-16% (v/v) LIX 79 (Hankel Corp.) diluted with n-heptane. The study of HFSLM includes the influence of hydrodynamic and chemical conditions, i.e., the flow rate of feed solution through the fibers, the lifetime of the system, the initial Au(I) concentration in the feed solution, the NaOH concentration in the stripping phase, and the pH of aqueous phases. A model is presented which describes the transport mechanism, indicating different rate-controlling steps. The validity of this model was evaluated with experimental data and found to tie in well with theoretical values. It was possible to achieve a 35-40-fold concentration in product (NaOH) in the presence of other metal cyanide salts such as Fe(II), Cu(I), Ni(II), and Ag(I) using the HFSLM technique. The effect of excess cyanide in the feed up to 1000 ppm did not affect the recovery of gold.