碘量法测定铁矿石中全铁及磁性铁的分析方法探讨

摘要

采用碘量法对不同类型铁矿石尤其是常规酸、碱分解方法难以分解完全的矿石中铁的测定进行分析研究,使用过氧化钠碱熔法测定全铁,并对传统磁性铁测定方法进行了改进.分析了不同酸度、碘化钾加入量、放置时间对测定结果的影响,以及干扰元素的影响及去除.实验方法全铁分析时过氧化钠加入量确定为3.0g,磁性铁分析时过氧化氢加入量确定为1滴(300 g/L);全铁和磁性铁分析反应起始酸度控制在0.5~1.0 mol/L,临近终点酸度控制在pH值为3.0~4.0;碘化钾溶液加入量为10 m L(250 g/L);并成功地分离了干扰元素.选取不同类型和含量的铁矿石标准物质和实际样品分别采用实验方法和传统的重铬酸钾无汞滴定法对全铁和磁性铁做方法对比试验,实验方法的测定结果与认定值或铬酸钾无汞滴定法的测定值基本一致.实验方法全铁测定结果的相对标准偏差(RSD)在0.076% ~0.19% 之间,磁性铁测定结果RSD在0.083% ~0.13% 之间,正确度与精密度均符合DZ/T 0130—2006质量管理规范的要求.%The determination of iron in iron ores(especially the ores which were hardly decomposed com-pletely by conventional acid and base decomposition method)by iodometry was analyzed and studied.Total iron was determined using sodium peroxide alkali fusion method.Moreover,the traditional determination method of magnetic iron was modified.The effect of acidity,addition amount of potassium iodide and pla-cing time on the determination results was investigated.The influence and elimination method of interfer-ence elements were studied.For the analysis of total iron in experiments,the addition amount of sodium peroxide was 3.0g.For the analysis of magnetic iron,the addition amount of hydrogen peroxide solution (300g/L)was one drop.The initial acidity was controlled at 0.5-1.0mol/L for the analysis of total iron and magnetic iron.The pH was controlled at about 3.0-4.0 near the endpoint of reaction.The addition amount of potassium iodide solution(250g/L)was 10mL.The interference elements were successfully separated.The content of total iron and magnetic iron in certified reference materials and actual samples of iron ore with different types and contents were determined using the experimental method and traditional potassium dichromate mercury-free titration for comparison.The found results of experimental method were basically consistent with the certified values or those obtained by potassium dichromate mercury-free titration method.The relative standard deviations(RSD)of determination results of total iron and magnetic iron were 0.076%-0.19% and 0.083%-0.13%,respectively.Both correctness and precision could meet the requirements of quality management standard in DZ/T 0130-2006.