Determination of Total Iron in Carbon-Containing Iron Ore by Perchloric Acid-Assisted Digestion and Potassium Dichromate Titration

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.