LIQUID EXTRACTION OF SILVER FROM THIOUREA SOLUTIONS
Abstract
The most famous method for precious metals extraction from ores and concentrates is hydrometallurgy and utilization of acidic thiourea solutions for precious metals leaching is an advisable alternative.
The leaching process is generally familiar and precipitation is prinnciple question in hydrometallurgical procedure of precious metals extraction from thiourea solutions.
At the present time there are several methods (cementation, electrolytical precipitation, adsorption on active carbon, ion sorbtion and liquid extraction) for silver precipitation from thiourea solutions.
The possibilities of silver precipitation from thiourea solutions by DEHPA (diethylhexyl phosphoric acid) and TBP (tributyl phosphate) using benzene and cyklohexanone as solvents has been studied.
Synthetic solution as well as real thiourea leachate solution has been used to study liquid extraction of precious metals from acidic thiourea solutions reached from Hodrusa's concentrate leaching.
The study of distribution coeficient of silver (DAg) vs. organic phase composition shows that maximum DAg at silver extraction from thiourea solutions is 0,675 at different proportion of DEHPA, TBP and benzene.
In following experiments the organic solvent - benzene was replaced by cyklohexanone and DAg was increased on 4,8 and extraction efficiency was 82%.
Distribution coeficient DAg was 21 and extraction efficiency was 95,45% when only TBP (50 vol.%) and cyklohexanone (50 vol.%) were used to extract silver from thiourea solutions.
Distribution coeficient of silver was lower in the solution reached from Hodrusa's concentrate acidic thiourea leaching then in synthetic one.
The presented work represent experimental study of selection of advisable extraction material for liquid extraction of silver from thiourea solutions.
The results show that the mixture of TBP and cyklohexanone appears the most suitable extraction matter for silver extraction from the thiourea solutions.
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