熔融制样-波长色散X射线荧光光谱法测定铌精矿石中铌锶钡硅铝铁等13种主次量元素

Determination of 13 Major and Minor Elements includings Nb, Sr, Ba, Si, Al, Fe in Niobium Concentrates by Wavelength Dispersive X-ray Fluorescence Spectrometry Using Fused Bead Sample Preparation

  • 摘要: 针对铌精矿石中铌锶钡等13种主次量元素的测定,现有电感耦合等离子体发射光谱法和质谱法(ICP-OES/MS)、分光光度法、重量法、比色法、原子吸收光谱法等常规方法,这些方法普遍存在样品预处理流程繁琐,且无法实现同一方法测定多个主次量元素的缺陷。对于岩石矿物中硅铝铁钙镁钾钠钛磷锰等造岩元素分析,对操作者有一定的经验要求,而对铌元素的测定采用酸溶或碱熔均存在共存元素干扰,测定结果不够准确。X射线荧光光谱法(XRF)具备快速批量分析优势,已应用于多种矿石检测。本文采用四硼酸锂-偏硼酸锂(质量比67∶33)混合熔剂熔融样品,使待测元素以稳定氧化物形式均匀分布于玻璃样片,有效解决基体效应、矿物效应、颗粒效应。通过钽矿石、铌精矿石、岩石成分分析标准物质及人工配制标准物质建立校准曲线,除铌、锶采用Rh Kα线康普顿散射强度作内标校正基体效应外,其余元素采用经验系数法来校正元素间的基体效应,并优化熔剂选择、稀释比等实验条件,解决Br对Al、Sn对Si、Y和Th对Nb等谱线干扰问题。经配制的铌矿石分析标准物质验证、方法比对,各元素检出限≤0.011%,相对标准偏差(RSD)≤3.05%(n=6),相对误差(RE)≤7.14%(n=6),符合DZ/T 0130.3—2006规范要求。该方法预处理简单、分析效率高,实现13种主次量元素同法同时测定,解决了传统方法的诸多难题。

     

    Abstract: For the determination of 13 major and minor elements (including Nb, Sr, Ba, etc.) in niobium concentrate, conventional techniques such as inductively coupled plasma-optical emission spectrometry/mass spectrometry (ICP-OES/MS), spectrophotometry, gravimetry, colorimetry, and atomic absorption spectrometry are widely adopted. These methods are generally plagued by cumbersome sample pretreatment procedures and the inherent limitation of being unable to simultaneously determine multiple major and minor elements. The analysis of rock-forming elements (e.g., Si, Al, Fe, Ca, Mg, K, Na, Ti, P, Mn) in rocks and minerals demands a certain level of operational experience. For Nb determination, both acid dissolution and alkali fusion approaches are susceptible to interference from coexisting elements, resulting in compromised result accuracy. X-ray fluorescence spectrometry (XRF) boasts the advantage of rapid batch analysis and has been extensively applied in the detection of various ores. In this work, samples were fused with a mixed flux of lithium tetraborate-lithium metaborate (mass ratio 67∶33), which ensured the uniform distribution of target elements in the form of stable oxides within glass pellets, thereby effectively eliminating matrix effects, mineral effects, and particle effects. Calibration curves were constructed using standard reference materials (SRMs) for tantalum ore, niobium concentrate, and rock composition analysis, as well as artificially synthesized standard reference materials. Matrix effect correction was performed using Rh Kα Compton scattering intensity as the internal standard for niobium and strontium, while the empirical coefficient method was employed for the other elements. Experimental parameters including flux selection, dilution ratio, pre-oxidation, fusion temperature, and holding time were optimized to address spectral interference issues (e.g., Br on Al, Sn on Si, Y and Th on Nb).Validation via artificially synthesized niobium ore standard reference materials and method comparison demonstrated that the limit of detection (LOD) for each element was ≤0.011%, the relative standard deviation (RSD) was ≤3.05% (n=6), and the relative error (RE) was ≤7.14% (n=6). These performance metrics comply with the requirements specified in the standard DZ/T 0130.3—2006 (Quality Management Specification for Testing in Geological and Mineral Laboratories). This proposed method offers simple pretreatment and high analytical efficiency, enabling the simultaneous determination of 13 major and minor elements with a single technique and overcoming numerous drawbacks of conventional methods.

     

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