Abstract：The content of metallic iron is the main indicator to evaluate the quality of direct reduction iron, which is an indispensable raw material to produce high-quality steel. Therefore, the determination of metallic iron content in direct reduction iron is of great significance to optimize steel structure and improve steel quality. Bromine-methanol non-aqueous system was selected to dissolve metallic iron (MFe) in direct reduction iron. The residue was separated by suction filtration with polytetrafluoroethylene (PTFE) microfiltration membrane (bore diameter of 0.45 μm). Metallic iron existed in the filtrate in the form of ferric tribromide, realizing its separation from other iron compounds with different valence. Sulfuric acid was added into the filtrate followed by adding hydrogen peroxide for several times. The solution was heated to form sulfuric acid smoke to remove bromide and methanol in the filtrate, which could avoid their interference with the determination of metallic iron. Most ferric irons in the filtrate were reduced to ferrous ions with stannous chloride. The residual ferric irons in the filtrate were reduced with titanium trichloride using sodium tungstate as the indicator. The excessive titanium trichloride was oxidized with dilute potassium dichromate solution. The content of ferrous ions was titrated with potassium dichromate standard solution using sodium diphenylamine sulfonate as the indicator. Consequently, a method for determination of metallic iron in direct reduction iron by potassium dichromate titration was established after separation with bromine-methanol non-aqueous system. Five direct reduction iron samples were selected to perform the precision tests according to the experimental method. The relative standard deviations (RSD, n=9) of the determination results were between 0.24% and 0.54%. The proposed method was applied for determination of metallic iron in two certified reference materials of direct reduction iron. The relative errors between the determination results and the certified values were between 0.012% and 0.15%.
胡晓静, 王雷, 富瑶, 陈新, 杨宇, 刘倩. 溴-甲醇非水体系分离-重铬酸钾滴定法测定直接还原铁中金属铁[J]. 冶金分析, 2022, 42(6): 70-75.
HU Xiaojing, WANG Lei, FU Yao, CHEN Xin, YANG Yu, LIU Qian. Determination of metallic iron in direct reduction iron by potassium dichromate titration after separation with bromine-methanol non-aqueous system. , 2022, 42(6): 70-75.
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