硫脲络合-火焰原子吸收光谱法同时测定银精矿中的铜和银

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

在高氯酸-硫脲介质中用原子吸收光谱法同时测定地质及选冶样品中银和铜已有文献报道;但在王水-硫脲介质中存在铜对银的测定干扰。本文采用盐酸-氢氟酸-硝酸-高氯酸四酸溶矿,王水提取、硫脲络合,用火焰原子吸收光谱法对银精矿中铜、银进行连续测定。通过筛选不同的样品消解方法,试验了硫脲介质浓度的影响,对共存元素的干扰进行消除。结果表明:四酸溶矿效果最好;通过加入过量的硫脲并控制其浓度在20 g/L以内,使溶液中银的白色沉淀与硫脲生成可溶的Ag[SC(NH2)2]3+配离子,消除了铜对银测定的干扰。该方法用于样品分析,相对标准偏差RSD(n=6)铜为1.20%～2.11%,银为0.61%～1.18%;加标回收率铜为96.5%～107.0%,银为97.3%～104.7%。测定值与碘量法、火试金法结果相符。本法具有简单、实用、成本低等优点,可满足银精矿选矿工艺生产的需要。

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 HC1-HF-HNO3-HC104 , 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 ] ; 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.