Improvement of determination method of molybdenum in ferromolybdenum by lead molybdate gravimetric method
LEI Honghong1, ZHOU Xiang1, SHI Ruiqi2, WANG Zhaohui3, CHEN Kai1, JIANG Peng*3
1. Beijing Phoenix Electronic Materials Technology Research Institute Co., Ltd., Beijing 100095, China; 2. China University of Geosciences Beijing, Beijing 100083, China; 3. University of Science and Technology Beijing, Beijing 100083, China
Abstract：Nitric acid and ammonium fluoride are used to dissolve ferromolybdenum in the lead molybdate gravimetric method for determining the content of molybdenum in ferromolybdenum in GB/T 5059.1-2014.After separating the interference elements such as iron with sodium hydroxide, Na2EDTA is added to further mask the interfering elements.Methyl orange indicator and tannin external indicator are used to determine the reaction endpoint.The hydrogen fluoride generated in thermal decomposition of ammonium fluoride will corrode the glass beaker.Moreover,this method also has some other shortcomings,for example,the operation of filtration and washing of hydroxide precipitation is time-consuming,the coloring of indicator is unclear,and many kinds of chemical reagents are used.To shorten the detection time and simplify the experimental process,the method above was improved:the ferromolybdenum sample was dissolved at low temperature of 50-70 ℃ with a mixed solution of acetic acid-nitric acid, the solution was boiled and evaporated to nearly dryness to remove the nitrogen oxides;then it was diluted with water to 150 mL,and 30 mL of Na2EDTA solution was added for complexation with iron,copper,and other impurity ions.In the medium of acetic acid-ammonium acetate buffer solution, 120 g/L lead acetate solution was added to fully convert molybdenum into lead molybdate precipitate. The precipitate was dried at 120 ℃, ashed in muffle furnace at 180 ℃, and then burned at 550 ℃.The sample was weighed to calculate the content of molybdenum.The experimental method was applied for the determination of molybdenum in three ferromolybdenum samples,and the relative standard deviation (RSD, n=5) of the results was less than 0.2%. The content of molybdenum in certified reference materials of ferromolybdenum was determined according to the experimental method,and the found results were consistent with the certified values.The improved method not only solved the corrosion problem of glass beaker by the solution, but also did not require sodium hydroxide precipitant and coloring indicator. It reduced the experimental error and shortened the test time,so this method was suitable for the rapid determination of molybdenum content in ferromolybdenum in production-type enterprises.
雷红红, 周详, 史锐奇, 王照辉, 陈凯, 蒋朋. 钼酸铅重量法测定钼铁中钼的方法改进[J]. 冶金分析, 2022, 42(5): 85-90.
LEI Honghong, ZHOU Xiang, SHI Ruiqi, WANG Zhaohui, CHEN Kai, JIANG Peng. Improvement of determination method of molybdenum in ferromolybdenum by lead molybdate gravimetric method. , 2022, 42(5): 85-90.
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