Separation and Concentration of Traces of Metallic Elements (Au, Hg, Pt, Pd) in Silver, Copper and Lead Metals by the Use of Sulfur as Collector

Abstract

A new separation and concentration method of traces of Au, Hg, Pt and Pd in silver, copper and lead metals using sulfur as collector is described. One ml of radioactive standard solution and 0.05-3 ml of (NH4)2S solution (Assay (as S): minimum 0.6%)were added to 35 ml of 0-5.5 HNO₃ solution containing 0.5 g (as metal base) of matrix element. Then, sulfur was produced by the following two procedures. (1) Rapid decomposition method: To the solution heated previously, 10-12 ml of conc. HNO₃ was added with stirring. (2) Slow decomposition method: 10-12 ml of conc. HNO₃ was added to the cold solution and the solution was heated with stirring.
The yield was determined by the measurement of r-activity with a 3 95x 3 NaI(T1) or 41 ml GOLD detector coupled to a multi-channel pulse height analyser. Test results: Better recovery and reproducibility were obtained by the former method. Optimum amount of (NH4)2S solution to be added was about 0.5 ml. Presence of excess of HNO₃ and HCl showed the tendency to decrease the concentration factor and recoveries of trace elements.
Au, Hg (in silver, copper and lead) and Pt (in copper) were collected almost quantitatively in sulfur. Recoveries of Pt (in lead) and Pd (in copper and lead) were not quantitative but reasonably high. Recoveries of Ag, Ir, Sb (in silver, copper and lead) and Pd (in silver) were low. Behavior of Hg in silver was interesting, because although Hg did not co-precipitate with Ag2S, it was collected almost quantitatively in sulfur.