Determination of Total Iron in Carbon-Containing Iron Ore by Perchloric Acid-Assisted Digestion and Potassium Dichromate Titration
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摘要:
快速、准确地测定铁矿石中的全铁含量，对于选矿研究和提升炼铁效率至关重要。铁矿石在炼铁前需经过选矿处理，采用磁选技术通常使用固态还原剂，如烟煤、褐煤等高碳物质。铁矿石试样中的高碳成分在溶解试样过程中难以完全去除，导致溶液浑浊甚至呈现深黑色，当采用SnCl2、TiCl3还原和重铬酸钾滴定法测定含固态还原剂铁矿石中的全铁时，无法直接进行测定。尽管可以通过先焙烧除碳再分析的传统方法测定全铁含量，但该方法误差大、分析周期长(2～4h)、能耗高。本文提出了在硫磷混合酸溶解试样过程中滴加高氯酸，去除试样中的碳，通过条件实验，确定了除碳最佳条件为在硫酸烟刚离开液面时滴加高氯酸。采用本方法测定由铁矿石标样和烟煤标样按不同比例配制的样品，全铁测定结果的相对标准偏差(RSD)为0.07%～0.43%，相对误差为0.10%～0.28%。对于固态还原剂为褐煤、焦炭、无烟煤、石墨分别与铁矿石标样按1∶1配制的样品，本方法有良好的除碳效果，RSD为0.25%～0.33%，相对误差为0.04%～0.19%。采用本方法和传统方法测定不同含碳量的实际样品，RSD分别为0.08%～0.40%和0.14%～0.68%，单个样品分析时间分别为30min和2～4h。与传统的焙烧法相比，本方法省去了焙烧试样除碳的步骤，降低了分析误差，并以简便的操作流程提升了工作效率，降低了能耗。
Abstract:Rapid and accurate determination of total iron content in iron ore is crucial for mineral processing research and improving iron-making efficiency. Iron ore needs to undergo beneficiation treatment before iron-making. Solid reducing agents, such as coal and brown coal, are commonly used in magnetic separation technology. However, the high carbon component in iron ore samples is difficult to completely remove during the dissolution process, resulting in cloudy or even black solutions. When SnCl2, TiCl3 reduction and potassium dichromate titration are used to determine total iron in iron ore containing solid reducing agents, direct determination of total iron becomes impossible. Although the traditional method of roasting to remove carbon before analysis can be used to determine the total iron content in iron ore, this method has large errors, a long analysis cycle (2−4h), and high energy consumption. A method is proposed here for removing carbon from the sample by adding perchloric acid during the dissolution process of sulfur phosphorus mixed acid, which has achieved good results. Through conditional experiments, the optimal condition for carbon removal was determined to be the drop-wise addition of perchloric acid when sulfuric acid smoke just left the liquid surface. This method was used to determine samples prepared from iron ore standard samples and bituminous coal standard samples in different proportions, with relative standard deviation (RSD) of 0.07%−0.43%, and relative error of 0.10%−0.28%. For samples prepared with solid reducing agents of lignite, coke, anthracite, and graphite in a 1∶1 ratio with iron ore standard samples, this method had good decarbonization effects, with RSD of 0.25%−0.33%, and relative error of 0.04%−0.19%. Using this method and the traditional method to determine actual samples with different carbon contents, the RSD ranged from 0.08%−0.40% and 0.14%−0.68%, respectively, and the analysis times for a single sample were 30min and 2−4h, respectively. Compared with the traditional roasting method, this method eliminates the step of removing carbon from roasted samples. It reduces the error of analysis results, improves work efficiency and reduces energy consumption with its simple operation process.
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Key words:
- potassium dichromate titration /
- iron ore /
- removing carbon /
- perchloric acid /
- solid reducing agents
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表 1 试样质量配比
Table 1. The mass ratio of samples
样品编号 质量配比(铁矿-煤) 试样1 1∶0 试样2 4∶1 试样3 1∶1 试样4 1∶4 
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表 2 不同质量配比烟煤存在下铁矿石全铁含量测试结果
Table 2. Analytical results of total iron content in iron ore in the presence of bituminous coal with different mass ratios
样品编号 TFe含量计算值
(%)TFe含量6次测定值
(%)TFe含量平均值
(%)RSD
(%)相对误差
(%)试样1 52.20 52.15 52.18 52.10 52.11 52.20 52.15 52.15 0.08 0.10 试样2 41.83 41.82 41.80 41.75 41.78 41.77 41.75 41.79 0.07 0.10 试样3 26.28 26.20 26.22 26.18 26.24 26.28 26.17 26.22 0.16 0.23 试样4 10.72 10.67 10.73 10.75 10.62 10.69 10.68 10.69 0.43 0.28
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表 3 不同质量配比固态碳存在下铁矿石全铁含量测试结果
Table 3. Analytical results of total iron content in iron ore in the presence of solid reductant with different mass ratios
样品名称 TFe含量计算值
(%)TFe含量6次测定值(%) TFe含量测定
平均值(%)RSD
(%)相对误差
(%)铁矿石-褐煤(1∶1) 26.34 26.30 26.39 26.33 26.19 26.22 26.29 26.29 0.27 0.19 铁矿石-焦炭(1∶1) 26.42 26.35 26.37 26.42 26.48 26.29 26.46 26.40 0.27 0.08 铁矿石-无烟煤(1∶1) 26.31 26.42 26.16 26.33 26.46 26.28 26.18 26.26 0.33 0.19 铁矿石-石墨(1∶1) 26.19 26.18 26.29 26.10 26.19 26.25 26.17 26.20 0.25 0.04
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表 4 不同方法测定全铁含量结果比对
Table 4. Comparison of analytical results of total iron content determined by different methods
样品编号 本方法测定TFe含量 传统焙烧法测定TFe含量 6次测定值(%) 平均值
(%)RSD
(%)6次测定值(%) 平均值
(%)RSD
(%)S1 31.22 31.28 31.19 31.29 31.17 31.24 31.23 0.15 31.29 31.17 31.10 31.31 31.14 31.18 31.20 0.26 S2 40.65 40.60 40.67 40.58 40.62 40.64 40.63 0.08 40.69 40.60 40.74 40.71 40.60 40.68 40.67 0.14 S3 25.53 25.49 25.40 25.44 25.47 25.52 25.48 0.19 25.59 25.45 25.42 25.48 25.58 25.57 25.52 0.29 S4 20.26 20.31 20.34 20.28 20.37 20.30 20.31 0.20 20.20 20.31 20.14 20.20 20.35 20.27 20.25 0.39 S5 11.13 11.18 11.16 11.23 11.20 11.11 11.17 0.40 11.10 11.22 11.19 11.29 11.20 11.09 11.18 0.68
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