EXTRACTION OF SILVER FROM CONCENTRATED CHLORIDE SOLUTIONS: USE OF TRI-n-BUTYL- AND TRI-n-OCTYLPHOSPHINE SULPHIDES

摘要

Tri-n-butyl- and tri-n-octylphosphine sulphides have been synthesised by reaction of the respective phosphines with sulphur, the results collected for their characterisation and purity being in accordance with expected data. Both alkylphosphine sulphides were then evaluated for silver extraction from concentrated chloride media, a stabilised sodium thiosulphate aqueous solution being utilised for the stripping of the metal ion. The selectivity of both extractants towards the precious metal, when 10-to 60-fold molar contents of Cu(II), Fe(III) and Pb(II) are present in the feed aqueous medium, was also investigated. The information obtained from the study of the dependency of silver ion distribution data on acid and chloride contents, as well as on extractant concentration, allows the proposal of the most probable silver extraction pathways. The overall results achieved are systematically compared with those previously obtained for triisobutylphosphine sulphide, commercially available from Cytec under the trade name of Cyanex 471X.