硫酸亚铁铵滴定法测定氯化稀土中氧化铈含量的方法研究

摘要

硫酸亚铁铵滴定法是测定稀土矿石和矿物中氧化铈含量的常用方法，其测定范围较宽为0.1%～50%氧化铈。试样在酸性溶液中，用过硫酸铵、高氯酸、铋酸钠等氧化剂将低价态的铈氧化成高价态，然后用适当浓度的硫酸亚铁铵标准溶液进行滴定。其实验分析操作过程主要包括试样的溶解、氧化、滴定三个部分。以GB/T16484-2009为主要指导方法，同时结合以浓H2SO4作为溶剂的硫酸亚铁铵滴定法，分别选用过硫酸铵和高氯酸作为氧化剂，邻菲罗啉和苯代邻氨基苯甲酸作为滴定指示剂，对取样量、溶矿方法、氧化条件、氧化时间、指示剂选择等多方面因素进行方法研究试验，确定方法最佳试验条件，从而有效解决了硫酸亚铁铵滴定法测定氯化稀土中氧化铈含量测试结果不稳定性和重现性不强等诸多问题，提高了方法的准确度和精密度。%The ammonium ferrous sulfate titrimetric method is a common method for determination of cerium oxide content in rare earth ores and minerals, its measuring range is wide ( 0.1%~50%cerium oxide). Low valence cerium in samples is first oxidized into high valence state in acidic solution by using oxidants, such as ammonium persulfate, perchloric acid, sodium bismuthate and so on. And then ammonium ferrous sulfate standard solution with appropriate concentration is used to titrate. The experimental operation process includes three parts of sample dissolution, oxidation and titration. In this paper, taking GB/T16484-2009 as the main guidance method, combining with the ammonium ferrous sulfate titrimetric method with concentrated sulfuric acid as solvent, sample was determined by respectively using ammonium persulfate and perchloric acid as oxidant, phenanthroline and phenyl anthranilic acid as titration indicator. Effect of sampling amount, mineral dissolution method, oxidation condition, oxidation time, indicator selection and other factors on determination result was investigated, optimal experimental conditions were obtained, which can effectively solve the problems of instability test results and poor reproducibility in the determination of cerium oxide content in rare earth chloride by the ammonium ferrous sulfate titrimetric method, improve accuracy and precision of the method.