碘-乙醇分离—重铬酸钾滴定法间接测定脱硫渣中金属铁

脱硫渣中金属铁的含量对其再利用具有重要的指导意义,因此测定脱硫渣中金属铁的方法受到关注。在采用碘-乙醇浸取—重铬酸钾滴定法直接测定脱硫渣中金属铁时,因碘-乙醇的存在会干扰后续重铬酸钾滴定法对金属铁的测定,故在过滤分离沉淀后,需在高温下除尽滤液中的碘-乙醇后再进行测定,不仅操作较繁琐,且存在一定的安全隐患。据此,提出了碘-乙醇分离—重铬酸钾法间接测定脱硫渣中金属铁的方法,并对测定条件进行了优化。称取两份相同质量的试样,一份试样采用重铬酸钾滴定法测定其中的全铁量;另一份试样用碘-乙醇浸取其中的金属铁,过滤分离,弃去滤液,采用相同方法测定沉淀中的全铁量;两者之差即为一份试样中的金属铁量,以此间接计算出试样中金属铁的含量。采用实验方法测定金属铁质量分数在0.63%~2.63%之间的脱硫渣生产试样,测定结果与碘-乙醇浸取—重铬酸钾滴定直接测定法相符,相对标准偏差(RSD,n=6)在3.1%~15.9%之间。选择2个脱硫渣生产试样,分别加入不同质量的纯铁进行加标回收试验,金属铁的加标回收率在96%~108%之间。

Indirect determination of metallic iron in desulfurization slag by potassium dichromate titration after iodine-ethanol separation

The content of metallic iron in desulfurization slag has important guiding significance for its reuse, so the determination method of metallic iron in desulfurization slag has attracted much attention. During the direct determination of metallic iron in desulfurization slag by potassium dichromate titration after iodine-ethanol leaching, the presence of iodine-ethanol will interfere with the subsequent determination of metallic iron in by potassium dichromate titration. Therefore, after filtration and precipitate separation, the iodine-ethanol in filtrate must be fully removed at high temperature before determination. As a result, the operation is cumbersome and time-consuming with certain security risks. On the basis of this problem, an indirect determination method of metallic iron in desulfurization slag by potassium dichromate titration after iodine-ethanol separation was proposed, and the measurement conditions were optimized. Two samples with same mass were tested. One of them was firstly determined by potassium dichromate titration to obtain the total iron content. The metallic iron in another sample was leached with iodine-ethanol. The filtrate was discarded after filtration and separation, and the content of total iron in precipitate was determined using same method. The difference value of total iron mass was the metallic iron mass in one sample. Thus the content of metallic iron in sample could be indirectly calculated. The proposed method was applied for the determination of production samples of desulfurization slag (the mass fraction of metallic iron was in range of 0.63%-2.63%). The found results were consistent with those obtained by direct determination using potassium dichromate titration after iodine-ethanol separation. The relative standard deviations (RSD, n=6) were between 3.1% and 15.9%. Different masses of pure iron were added into two production samples of desulfurization slag for the recovery tests. The recoveries of metallic iron were between 96% and 108%.