微波消解-电感耦合等离子体发射光谱法测定石煤钒矿中钒铝铁钛铜锰镍磷

Determination of Vanadium, Aluminum, Iron, Titanium, Copper, Manganese, Nickel, and Phosphorus in Stone Coal Vanadium Ore by Microwave Digestion-Inductively Coupled Plasma-Optical Emission Spectrometry

  • 摘要: 石煤钒矿已成为全球钒产品的重要来源,准确测定其成分是勘探、研究和综合利用的一项基础工作。石煤钒矿中钒、铝、铁、钛、磷含量为10−2量级,铜、锰、镍含量为10−6量级。采用电感耦合等离子体发射光谱法(ICP-OES)测定上述元素的效果较好,但碱熔时背景干扰及检出限较高;酸溶需先灼烧除碳,过程繁琐;不灼烧敞开酸溶时易残留碳渣。本文试验优选了硝酸-氢氟酸-硫酸(体积比3∶2.5∶1)三元体系及消解条件,于最高消解温度220℃、梯度升温30 min、消解1.5 h实现样品湿法充分消解,并于180℃和260℃分段平稳赶酸。建立了微波消解ICP-OES测定石煤钒矿中8种元素的方法。结果表明:在微波高温密闭条件下,硫酸提供持续的高温液态环境并脱水氧化,氢氟酸破坏硅酸盐晶格,硝酸和硫酸彻底氧化碳质,三酸协同实现硅质碳质石煤钒矿样品的充分消解。方法检出限为0.0005% ~ 0.003%,精密度为0.91% ~ 3.8% (RSD,n = 7),标准物质的测定值与标准值一致。课题组前期采用的五酸敞开溶矿难以将高碳质彻底氧化,但残留碳质中基本不含待测元素,测定结果准确;本研究采用微波消解可彻底消除高碳质,待测溶液透明澄清,两种方法均满足测定要求。对于碳质含量高于15%的样品,建议优先采用微波消解法;碳质含量低于15%的样品,若批量大且检测效率要求高,建议优先采用五酸敞开溶矿法。

     

    Abstract: Stone coal vanadium ore has become an important source of vanadium products globally. Accurate determination of its composition is a fundamental task for exploration, research, and comprehensive utilization. The contents of V, Al, Fe, Ti, and P in stone coal vanadium ore are on the order of 10−2 wt%, while those of Cu, Mn, and Ni are on the order of 10−6 wt%. Inductively coupled plasma-optical emission spectrometry (ICP-OES) performs well for the determination of these elements, but alkali fusion suffers from high background interference and detection limits; acid digestion requires pre-ashing to remove carbon, which is cumbersome; and open acid digestion without ashing tends to leave residual carbonaceous slag. In this work, a ternary acid system of HNO3-HF-H2SO4 (volume ratio 3:2.5:1) and digestion conditions were optimized. Complete wet digestion of the samples was achieved at a maximum digestion temperature of 220℃, with a gradient heating ramp of 30 min and digestion for 1.5 h, followed by stepwise acid evaporation at 180℃ and 260℃. A method for the determination of eight elements in stone coal vanadium ore by microwave digestion coupled with ICP-OES was established. The results indicate that under high-temperature sealed microwave conditions, sulfuric acid provides a sustained high-temperature liquid environment and promotes dehydration-oxidation, hydrofluoric acid breaks the silicate lattice, and nitric acid together with sulfuric acid thoroughly oxidizes the carbonaceous matter. The synergistic action of the three acids enables complete digestion of siliceous carbonaceous stone coal vanadium ore samples. The detection limits of the method range from 0.0005% to 0.003%, with precision (RSD, n=7) of 0.91% to 3.8%. The determined values for certified reference materials agree well with the certified values. The previously employed five-acid open digestion method by our group could not completely oxidise high-carbonaceous matter; however, the residual carbon contained essentially none of the target elements, so the results remained accurate. In contrast, microwave digestion can completely eliminate high-carbonaceous matter, yielding a clear and transparent solution. Both methods satisfy the analytical requirements. For samples with a carbon content exceeding 15%, microwave digestion is recommended as the preferred option; for samples with a carbon content below 15%, particularly when processing large batches with high throughput demands, the five-acid open digestion method is advisable.

     

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