1. State Key Laboratory for Research and Comprehensive Utilization of Rare Earth Resources in Bayan Obo, Baotou 014030, China; 2. Baotou Research Institute of Rare Earths, Baotou 014030, China; 3. National Engineering Research Centre of Rare Earth Metallurgy and Function Materials, Baotou 014030, China
Abstract：High purity zirconium oxychloride is an important raw material for the production of high purity zirconium chemicals. As a common impurity element in high purity zirconium oxychloride, the content of iron is in range of 0.000 1%-0.005 0% (mass fraction, the same below). The accurate determination of iron content is of great significance for the research of high purity zirconium oxychloride production technology and its downstream application. The sample was dissolved with hydrochloric acid (1+1). Based on the characteristic that potassium thiocyanate and 1, 10-phenanthroline could react with iron in sample in the dilute hydrochloric acid medium to form a purplish red ternary complex, a method for determination of trace iron in high purity zirconium oxychloride was established by potassium thiocyanate and 1, 10-phenanthroline coloring spectrophotometry with methyl isobutyl ketone extraction. The determination conditions were optimized as follows: the volume of hydrochloric acid in the coloring system was 1.0-2.5 mL. 2.0 mL of 500 g/L potassium thiocyanate solution and 2.0 mL of 2.5 g/L 1, 10-phenanthroline ethanol solution were added. After vibration for 10 s and coloring for 1 min, 5.0 mL methyl isobutyl ketone was added for extraction with 30 s oscillation. The absorbance of solution was measured at 520 nm by spectrophotometer. The results showed that the iron content in coloring system in range of 0.50-16 μg had a good linear relationship with its corresponding absorbance, and the linear correlation coefficient of the calibration curve was r=0.999 7. The molar absorption absorptivity was 2.081 8×104 L·mol-1·cm-1. The detection limit of the method was 0.000 048%. The contents of iron in three high purity zirconium oxychloride samples were determined according to the proposed method. The relative standard deviations (RSD, n=11) were between 2.6% and 9.0%, and the recoveries were between 96% and 107%.
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