铅试金-硫氰酸钾滴定法测定铂钯精矿中银

准确测定铂钯精矿中银含量对其高效综合利用具有重要的指导意义。铂钯精矿中银含量高、基体复杂、测定难度大。采用铅试金预富集样品中的银,以留铅灰吹法避免银在灰吹时的损失;再用硝酸溶解铅珠,用丁二酮肟沉淀分离钯,消除钯对滴定终点颜色的干扰;最后用硫氰酸钾滴定法滴定银,建立了铅试金-硫氰酸钾滴定法测定铂钯精矿中银的分析方法。试验表明:经铅试金预富集银后,灰吹留铅量为2～3 g时可以减少银的损失;用4 mol/L硝酸消解铅珠,36 mL丁二酮肟乙醇溶液分离除去钯,能有效消除钯对测定的干扰。按照实验方法测定铂钯精矿实际样品和模拟样品中银,实际样品测定结果的相对标准偏差(RSD,n=7)为0.50%～0.72%,加标回收率为96%～101%,模拟样品的测定值与理论值吻合。

Determination of silver in platinum-palladium concentrate by potassium thiocyanate titration with lead fire assay

The accurate determination of silver in platinum-palladium concentrate has important guiding significance for its efficient and comprehensive utilization. However, the content of silver in platinum-palladium concentrate is high, and the matrix is complex, leading to high difficulty in determination. Silver in sample was preconcentrated with lead fire assay, and the loss of silver in cupellation was avoided by remaining lead cupellation. Then the lead beads were dissolved with nitric acid. Palladium was separated by dimethylglyoxime precipitation method, thus eliminating the interference of palladium with the titration end point color. Finally, silver was titrated with potassium thiocyanate titration. Consequently, a method for determination of silver in platinum-palladium concentrate was established by potassium thiocyanate titration combined with lead fire assay. The experimental results showed that the loss of silver could be reduced when the remaining lead in cupellation was 2-3 g after preconcentrating silver via lead fire assay. After lead beads was digested with 4 mol/L nitric acid and palladium was separated with 36 mL of dimethylglyoxime ethanol solution, the interference of palladium with the determination could be effectively eliminated. The content of silver in actual samples and simulated samples of platinum-palladium concentrate were determined according to the proposed method. For the actual sample, the relative standard deviations (RSD, n=7) of the results were between 0.50% and 0.72%, and the recoveries were between 96% and 101%. For the simulated samples, the results were consist with the theoretical values.