Determination of Wolfram in Tungsten Ore by Pressurized Acid Digestion-Inductively Coupled Plasma-Atomic Emission Spectrometry
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摘要:
由于钨在酸性介质中极易发生水解生成水合三氧化钨,通常将钨矿石样品碱熔后采用重量法、光度法等传统方法进行测定,但这些方法操作繁琐,称样量较大(0.1~0.5 g)。本文采用封闭压力酸溶分解样品,钨矿石样品在170℃密闭20 h,然后迅速溶解于10%氢氟酸和5%浓硝酸的混合酸中,使钨形成稳定的易溶解的六价配合物,用耐氢氟酸进样系统的电感耦合等离子体光谱仪测定其中钨的含量,方法精密度为1.5%~6.4%(RSD,n=10),检出限为0.039~0.042 μg/g。方法经钨矿石国家标准物质验证,测定值与标准值一致;与分光光度法对照,测定结果吻合。本方法有效地解决了钨在酸性介质中极易水解的问题,溶样时间相对较短(20 h),无需进行赶酸、复溶等步骤,操作简单,可满足钨含量在0.015%~50%范围的钨矿石的日常分析要求。
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关键词:
- 钨矿石 /
- 钨 /
- 封闭压力酸溶 /
- 氢氟酸 /
- 电感耦合等离子体发射光谱法
Abstract:Tungsten is prone to hydrolysis of hydrated tungsten oxide in acidic medium, so it is usually measured using traditional methods of weight method and spectrophotometry after alkaline fusion, which needs complex operation and large sampling size (0.1-0.5 g). A new method of analysis of tungsten ores has been established by using pressurized acid digestion and a hydrofluoric acid system for Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) and is described in this paper. Tungsten ores were effectively decomposed at 170℃ for 20 h, and then the samples were quickly dissolved in mixed acids of 5% hydrofluoric acid and 10% nitric acid. Tungsten in the form of the stable eutectic hexavalent complexes was determined by ICP-AES with a hydrofluoric acid resistant device. The detection limits of this method are 0.039-0.042 μg/g. Both the accuracy and precision of the method were validated by analyzing standard reference materials GBW 07240, GBW 07241, with 1.53%-6.42% (RSD, n=10). The results were in good agreement with the certified values of the national standard materials. This method can effectively solve the problems of tungsten hydrolysis easily in acidic medium. The operation is simple and has a relatively short digestion time of 20 h. The method can be used to analyze tungsten content in the range of 0.015%-50%.
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表 1 标准系列浓度
Table 1. The concentrations of standard solution
元素 浓度(μg/mL) 系列1 系列2 系列3 系列4 系列5 系列6 系列7 系列8 Mo 20 50 100 300 - - - - W 5 10 25 50 - - - - Cu - - - - 5 10 20 - Li - - - - 5 10 20 - 表 2 元素波长和背景扣除
Table 2. Wavelength and background deduction used in ICP-AES analysis
元素 分析波长(nm) 级次 谱线强度 背景扣除位置 左 右 Cu 324.752 103 5000 1 15 Li 670.784 050 12000 3 12 Mo 202.030 166 500 1 12 203.845 165 250 1 15 W 224.876 149 180 5 15 239.708 140 250 1 12 表 3 不同浓度和酸度测定结果
Table 3. Analytical results of W in standard solution under different pretreatment conditions
溶液介质(酸度) 钨的测定值(μg/mL) 10 μg/mL钨标准溶液 25 μg/mL钨标准溶液 50 μg/mL钨标准溶液 1%氢氟酸,5%硝酸 9.48 24.1 46.7 5%氢氟酸,5%硝酸 9.88 25.2 49.0 10%氢氟酸,5%硝酸 10.2 25.8 50.0 15%氢氟酸,5%硝酸 10.3 26.1 50.8 20%氢氟酸,5%硝酸 10.6 26.3 49.5 表 4 标准溶液放置3天后的测定结果
Table 4. Analytical results of W in standard solution after standing for 3 days in sample preparation
溶液介质(酸度) 钨的测定值(μg/mL) 10 μg/mL钨标准溶液 25 μg/mL钨标准溶液 50 μg/mL钨标准溶液 1%氢氟酸,5%硝酸 9.71 24.6 47.1 5%氢氟酸,5%硝酸 10.0 25.7 49.1 10%氢氟酸,5%硝酸 10.4 25.8 50.6 15%氢氟酸,5%硝酸 10.6 26.4 50.8 20%氢氟酸,5%硝酸 10.8 26.4 49.6 表 5 样品分解温度及时间实验结果
Table 5. Analytical results of W under different decomposition temperature and time
溶矿温度(℃) 钨的标准值(μg/g) 钨的测定值(μg/g) 溶矿12 h 溶矿16 h 溶矿20 h 130 3465 3424 3603 150 3600 3488 3639 3635 170 3611 3683 3656 表 6 方法的精密度和准确度
Table 6. Precision and accuracy tests of the method
标准物质编号 项目 W Cu Li Mo 224.876nm 239.708nm 324.752nm 670.784nm 202.03nm 203.845nm GBW07240(钨矿石) 标准值(μg/g) 150±30 150±30 790±40 200 4.2±1.2 4.2±1.2 测定均值(μg/g) 138 149 761 193 - - RSD(%) 6.1 4.1 6.4 3.9 - - 相对误差(%) -8.26 -0.89 -3.63 -3.51 - - GBW07241(钨矿石) 标准值(μg/g) 2200±200 2200±200 960±40 300 980±60 980±60 测定均值(μg/g) 2212 2245 950 277 1017 1032 RSD(%) 1.6 1.5 1.8 2.7 1.7 1.7 相对误差(%) 0.54 2.06 -1.00 -7.62 3.77 5.26 注:GBW 07240中,Mo的测定结果较低,低于ICP-AES测定下限。 表 7 本方法与国家标准方法检测结果
Table 7. Analytical results of W in samples by standard method and ICP-AES
样品名称 钨的测定值(%) 硫氰酸钾-三氯化钛光度法 本法(ICP-AES) 黑钨矿石 0.13 0.13 白钨矿石 0.44 0.44 黑钨精矿 48.4 48.0 GBW 07241(钨矿石) 0.22 0.22 GBW 07284(钨矿石) 3.67 3.67 表 8 方法检出限
Table 8. The detection limits of the method
测定元素 波长(nm) 方法检出限(μg/g) Cu 324.752 0.015 Li 670.784 0.007 Mo 202.030 0.016 203.845 0.037 W 224.876 0.039 239.708 0.042 -
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[5] [6] [7] GB/T 14352. 1—2010, 钨矿石、钼矿石化学分析方法[S].
[8] [9] [10] [11] [12] GB/T 6150—2008. 1—2010, 钨精矿化学分析方法[S].
[13] GB/T 4324—2008. 钨化学分析方法[S].
[14] GB/T 14352—201. 钨矿石、钼矿石化学分析方法[S].
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