Improvement of ion exchange separation-Na2EDTA titration for the determination of zinc in nickel-cobalt-zinc concentrate
ZUO Hongyi1, LIN Ruoxu2
1. Shenzhen Zhongjin Lingnan Nonferrous Metals Co., Ltd. Science and Technology Development Institute, Shaoguan 512024, China; 2. China Nonferrous Metals Industry Standard Metrology and Quality Institute, Beijing 100080, China
Abstract：With the increasing depletion of zinc resources, the composition of zinc concentrates becomes more and more complex. It is of great significance to accurately determine the content of zinc in zinc concentrate. In experiments, the sample was dissolved with hydrochloric acid- ammonium fluoride-nitrate acid-sulfuric acid-perchloric acid. In the medium of hydrochloric acid (1+5), the metal elements including nickel, cobalt, iron, manganese and aluminum were separated with macro-reticular type strong alkaline anionic resin. Zn2+ was eluted with ammonia-ammonium chloride solution. A small amount of ammonium fluoride and sodium hyposulfite was added into the solution after impurity separation to mask the residual iron and trace copper, respectively. The total contents of zinc and cadmium were directly titrated with Na2EDTA standard titration solution. The content of zinc could be obtained by deducting the cadmium content. Consequently, a method for determination of zinc (11%-62%) in nickel-cobalt-zinc concentrate by Na2EDTA titration with ion exchange separation was established. The partition coefficients (Kd) of metal ions on three typical strong alkaline anion resins with different acidity were investigated. The ion exchange separation conditions were finally selected as follows: D296 macro-reticular type strong alkaline anionic exchange resin and hydrochloric acid (1+5) medium. The test results showed that the presence of little NH+4 would not influence on the adsorption of Zn2+. The adsorption loss rate was less than 0.10% when the height of ion exchange column was 30 cm. The working efficiency was high and adsorption loss rate was low when the flow rate of sample solution through ion exchange column was in range of 8-10 mL/min. The proposed method was applied for the determination of zinc in three nickel-cobalt-zinc concentrate samples, and the found results were basically consistent with those obtained by sodium hydroxide precipitation separation-EDTA titration and dimethylglyoxime precipitation separation-EDTA titration. The relative standard deviations (RSD, n=11) of determination results were between 1.6% and 5.6%.
左鸿毅, 林若虚. 离子交换分离-Na2EDTA滴定法测定含镍钴锌精矿中锌的改进[J]. 冶金分析, 2022, 42(7): 46-53.
ZUO Hongyi, LIN Ruoxu. Improvement of ion exchange separation-Na2EDTA titration for the determination of zinc in nickel-cobalt-zinc concentrate. , 2022, 42(7): 46-53.
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