氢化物发生分离去除锑干扰-火焰原子吸收光谱法测定高锑岩石矿物中的金

Determination of Gold in High-Antimony Rocks and Minerals by Flame Atomic Absorption Spectrometry with Hydride Generation Separation to Eliminate Antimony Interference

  • 摘要: 金是全球关键稀缺矿产资源,高锑岩石矿物是金矿化的重要载体,其中金常以微细粒自然金、硫化态金或包裹态赋存,高锑含量会严重干扰金的精准测定。现有方法难以同时解决“金无包裹损失” “还原体系稳定高效” “锑彻底脱除”三大难点,制约此类资源的精准评估与高效开发,主要问题是难以在避免金损失的前提下实现锑的彻底脱除与稳定还原。本文提出“分步焙烧、还原转化、氢化物发生分离”的前处理思路,通过系列试验明确干扰来源,采用阶梯式焙烧避免金颗粒包裹,在硫脲-抗坏血酸复合体系中将锑完全转化为Sb(Ⅲ),并结合活性炭动态富集-火焰原子吸收光谱法(FAAS)测定金含量。标准物质和实际样品验证表明:当锑含量高于18%时,样品焙烧结块,溶液中锑量大于60 mg (6%)时干扰金分析;最优除锑条件为硼氢化钾用量1.5 g(浓度15%,加入量10 mL),锑去除率与金回收率均>95%;金检出限为0.028 μg/g,检测范围为0.12 ~ 50 μg/g;标准物质测定相对误差为1.75% ~ 2.32%,RSD为2.70% ~ 3.58%,优于国标方法;实际样品加标回收率为97.2% ~ 102.3%,t检验值均<2.571,符合《地质矿产实验室测试质量管理规范》(DZ/T 0130—2006)要求。该方法可有效消除锑干扰,为同类干扰基体的贵金属分析提供参考。

     

    Abstract: Gold is a globally critical and scarce mineral resource. High-antimony rocks and minerals are important carriers of gold mineralization, where gold usually occurs as fine-grained native gold, sulfide-bound gold, or encapsulated gold, and high antimony content seriously interferes with the accurate determination of gold. Existing methods cannot simultaneously solve the three core difficulties of “no encapsulation loss of gold”, “stable and efficient reduction system” and “complete removal of antimony”, which restricts the accurate evaluation and efficient development of such resources, and the core scientific problem is how to achieve complete removal and stable reduction of antimony while avoiding gold loss. To address this problem, this paper proposes a strategy of “stepwise roasting, reduction transformation, and hydride generation separation”, clarifies the nature of interference through a series of experiments, uses stepwise roasting to avoid encapsulation of gold particles, completely converts antimony to Sb(Ⅲ) in the thiourea-ascorbic acid composite system, and determines the gold content by flame atomic absorption spectrometry (FAAS) combined with dynamic enrichment with activated carbon. Verification with reference materials and actual samples shows that when the antimony content is higher than 18%, the sample sinters during roasting; when the antimony content in the solution is more than 60 mg (6%), it interferes with gold analysis; the optimal antimony removal conditions are 1.5 g of potassium borohydride (15% concentration, 10 mL dosage), with both antimony removal rate and gold recovery rate >95%; the detection limit of gold is 0.028 μg/g, and the detection range is 0.12–50 μg/g; the relative errors of reference material determination are 1.75%–2.32%, and the RSDs are 2.70%–3.58%, which are better than those of the national standard method; the spiked recovery rates of actual samples are 97.2%–102.3%, and the t-test values are all <2.571, meeting the requirements of Specification for Testing Quality Management of Geological and Mineral Laboratories (DZ/T 0130—2006). This method can effectively eliminate antimony interference and provide a reference for the analysis of precious metals in similar interference matrices.

     

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