Simultaneous Determination of Copper and Silver in Silver Concentrate by Atomic Absorption Spectrometry after Theorem Completion

A method has been reported in articles for the simultaneous determination of copper and silver in geological samples or samples of mineral processing and smelting by Atomic Absorption Spectrometry in an aqua regia-thiourea medium. However, interference from copper made the determination of silver in the aqua regia-thiourea medium difficult. In this paper, a method is decribed whereby the sample was dissolved with a four-acid system of HCl-HF-HNO₃-HClO₄, extracted by aqua regia and chelated by theorem. The continuous determination of silver and copper in silver concentrate was made by Flame Atomic Absorption Spectrometry (FAAS) in an aqua-thiourea medium. The interference of coexisting elements was eliminated by testing different sample digestion methods and different concentrations of the thiourea medium. The results show that the samples were completely dissolved with the four-acid system. By adding excessive amounts of thiourea within the 20 g/L, the white precipitation of Ag was completely transformed into the Ag[SC(NH₂)₂]₃⁺ ion in order to eliminate interference from copper. This method was applied to the analysis of samples with relative standard deviations (RSD, n=6) for Cu and Ag in the range of 1.20%-2.11% and 0.61%-1.18%. With the standard addition, the recoveries for Cu and Ag were in the range of 96.5%-107.0% and 97.3%-104.7%. The determination results are in agreement with fire assay and iodometry results. The method has the merits of easy, practicality and low cost, which meet the demands for silver concentrate processing.