Use of modified membrane carrier system for recovery of gold cyanide from alkaline cyanide media using hollow fiber supported liquid membranes: feasibility studies and mass transfer modeling

This investigation is concerned with the applications of hollow fiber suppo rted liquid membranes for the recovery of gold(I) (Au(CN)(2)(-)) from alkal ine cyanide media using microporous hydrophobic hollow fiber with modified membrane extractant (carrier). The organic extractant used fur gold(I) perm eation was LIX79 alone and mixture of TOPO+LIX79 diluted with n-heptane. Th e mixture of LIX79+TOPO affords better performance than LIX79 alone. P-Au v alue was 2.8 x 10(-5) cm/s with LIX79 alone, whereas P-Au value was found t o be 9.5 x 10(-5) cars with only TOPO membrane carrier. Transport of Au(CN) (2) from alkaline cyanide solutions with TOPO alone was also observed indic ating gold(I) complexation takes place most likely by solvation reaction me chanism (M+...Au(CN)(2). S-n). The permeability of Au(I) was enhanced by 22 0 folds by using mixture of TOPO+LIX79 with respect to only LIX79 and 57 ti mes with respect to only TOPO while maintaining aqueous feed at pH 10.3. A model is presented which describes the transport mechanism, indicating diff erent rate-controlling steps. The validity of this model was evaluated with experimental data and found to tie in well with theoretical values. In add ition, selectivity of Au(I) with respect to Zn(II) and Ag(I) cyanide salts was improved. It was possible to recover Au(I) in presence of other metal c yanide salts of Fe(II), Cull), Ni(II), Ag(I) and Zn(II) which approves the potential of mixture of extractants (TOPO+LIX79) for hydrometallurgical sol utions. (C) 2000 Elsevier Science B.V. All rights reserved.