RECOVERY OF AG AND AU FROM AQUEOUS THIOUREA SOLUTIONS BY LIQUID-LIQUID EXTRACTION

摘要

In order to replace CN~- ions in the leaching of gold and silver, systems which employ thiourea have been investigated. In this paper, the results of silver and gold ion recovery, by liquid-liquid extraction, from aqueous thiourea solutions which originate from ore dissolution processes are discussed. The influence of thiourea on the extraction efficiency of the metal ions is studied. The highest extractions in the presence of thiourea were obtained when the aikylthiophosphinic acids Cyanex 302 and Cyanex 301 were used. To elucidate the nature of the species extracted into the organic phase, a simple thermodynamic model of extraction is proposed for the case of the extraction of gold(Ⅰ) from H_2SO_4/thiourea media. In this model, the complexation of the metal ion with thiourea in the aqueous phase is taken into account through a side reaction coefficient.