The separation of nickel(II) from base metal ions using 1-octyl-2-(2鈥?pyridyl)imidazole as extractant in a highly acidic sulfate medium

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• 作者：Adeleye I. Okewole ; Nomampondo P. Magwa ; Zenixole R. Tshentu ; ^{z.tshentu@ru.ac.za}
• 关键词：Nickel ; Pyridylimidazole ; Base metals ; Sulfate medium
• 刊名：Hydrometallurgy
• 出版年：2012
• 期刊代码：38_0304386x
• 类别：ce
• 出版时间：June, 2012
• 卷：121-124
• 期：Complete
• 页码：81-89
• 文件大小：1332 K

摘要

In this study, 1-octyl-2-(2鈥?pyridyl)imidazole (OPIM), along with dinonylnaphthalene sulfonic acid (DNNSA) as a synergist, was investigated as a potential selective extractant of Ni^2 + from base metals in a solvent extraction system using 2-octanol/Shellsol 2325 (4:1) as a diluent and modifier, respectively. The separation of Ni^2 + from the borderline and hard acids; Co^2 +, Cu^2 +, Zn^2 +, Fe^2 +, Fe^3 +, Mn^2 +, Mg^2 + and Ca^2 + was carried out at a pH range of 0.5-3.5 in sulfate and sulfate/chloride media. The separation of Ni^2 + from Co^2 + in 0.001 M solutions was achieved with an optimised concentration of 0.025 M OPIM along with 0.02 M DNNSA to the tune of a 鈭唒H_陆 鈮?#xA0;1.6. The extraction system further proved the rejection of 0.001 M Fe^3 +, Mn^2 +, Mg^2 + and Ca^2 +. The absence of DNNSA resulted in very low extraction efficiencies of the Ni^2 + metal ions in the pH range under investigation, thus highlighting the role of the synergist (DNNSA). The three-stage counter-current extraction of Ni^2 +, at the optimised pH of 1.89, from a synthetic mixture of Ni^2 +, Co^2 + and Cu^2 +, yielded 99.01 (卤 1.79)%. The total co-extracted Cu^2 + was 48.72 (卤 0.24)%of the original quantity in the mixture, and it was 19.85 (卤 0.28%) for Co^2 +. The co-extracted Cu^2 + was scrubbed off from the loaded organic phase at pH 鈮?#xA0;8.5 by using an ammonium buffer, while co-extracted Co^2 + was selectively and quantitatively stripped with H₂SO₄ at pH 1.64. The total recovery of Ni^2 + by stripping at pH 0.32 was 94.05 (卤 1.70)%. The underlying chemistry in this extraction system was studied through solid state/solution studies for the complexation of the ligand with the base metals, and it is apparent from the qualitative/semi-quantitative data that the separations achieved are of kinetic origin rather than thermodynamic, nor are they being driven by stereochemical preferences. Therefore, 1-octyl-2-(2鈥?pyridyl)imidazole can be effectively utilized alongside DNNSA as a co-extractant in the separation of Ni^2 + from base metals in acidic sulfate and sulfate/chloride media.