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

摘要

This investigation is concerned with tbe applications of hollow fiber supported liquid membranes for the recovery of gold(I) (Au(CN)_2) from alkaline cyanide media using microporous hydrophobic hollow fiber with modified membrane extractant (carrier). The organic extractant used for gold(I) permeation was LIX79 alone and mixture of TOPO+LIX79 diluted with n-heptane. The mixture of LIX79+TOPO affords better performance than LIX79 alone. P_Au value was 2.8 x l0~-5 cm/s with LIX79 alone, whereas P_Au value was found to be 9.5 x l0~-5 cm/s with only TOPO membrane caITer Transport of Au(CN)_2 from alkaline cyanide solutions with TOPO alone was also observed indicating gold(I) complexation takes place most likely by solvation reaction mechanism (M~+... Au(CN)_2.S_n). The permeability of Au(I) was enhanced by 220 folds by using mixture of TOPO+LIX79 with respect to only LIX79 and 57 times with respect to only TOPO while maintaining aqueous feed at pH I0.3. 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. In addition, selectivity of Au(I) with respect to Zn(Il) and Ag(I) cyanide salts was improved. It was possible to recover Au(I) in presence of other metal cyanide salts of Fe(II), Cu(l), Ni(II), Ag(I) and Zn(II) which approves the potential of mixture of extractants (TOPO+LIX79) for hydrometallurgical solutions.