Base metal hydrometallurgy in a chloride medium has considerable advantages, as metals can be recovered by solvent extraction through a neutral complex mechanism without extra reagent addition, leading to ready lixiviant recycling and significantly reduced wastewater discharge. However, the recovery of Ni(II) using this hydrometallurgical method is challenging because of the unavailability of appropriate extraction reagents. In this study, a new reagent, N-2-ethylhexylpyridine-3-formamide (MEH3), was used to efficiently extract Ni(II) from weakly acidic (pH > 2.5) or neutral chloride solutions in the form of neutral complexes without pH adjustment. Some other metal ions can also be extracted; the selectivity of the reagent for each metal decreased in the following order: Cu(II) > Zn(II) > Ni(II) > Fe(III) > Co(II) > Mn(II). The reagent had weak ability to extract other metal ions such as Ca, Al, Cr(III), Mg, and Li. The extraction of Ni(II) was positively correlated with the Cl concentration in the aqueous solution, indicating that Cl is a driving force for Ni(II) extraction. The Ni(II) loaded organic phase was stripped with water, and approximately 50 g/L of Ni(II) in the loaded strip liquor was obtained at an O/A ratio of 15:1. The Ni(II) extraction mechanism was further studied using crystal structure analysis, FT-IR spectroscopy, and the maximum loading capacity. The results showed that a Ni(MEH3)Cl complex was formed via Ni(II) extraction. In conclusion, the MEH3 system can selectively extract Ni(II) from a chloride solution without consuming alkaline reagents, and no new substances are produced, which is beneficial for the realization of mother liquor recycling and has a positive impact on clean hydrometallurgy.

中文翻译：

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使用 N-2-乙基己基吡啶-3-甲酰胺从氯化物溶液中萃取镍 (II)：清洁湿法冶金的新试剂以及红土镍矿氯化物浸出液的拟议流程


在氯化物介质中进行贱金属湿法冶金具有相当大的优势，因为可以通过中性复杂机制通过溶剂萃取来回收金属，无需添加额外的试剂，从而实现浸滤剂的回收并显着减少废水排放。然而，由于缺乏合适的萃取试剂，使用这种湿法冶金方法回收 Ni(II) 具有挑战性。在本研究中，使用一种新试剂 N-2-乙基己基吡啶-3-甲酰胺 (MEH3)，以中性络合物的形式从弱酸性 (pH > 2.5) 或中性氯化物溶液中高效萃取 Ni(II)，无需考虑 pH 值调整。还可以提取其他一些金属离子；试剂对每种金属的选择性按以下顺序降低：Cu(II) > Zn(II) > Ni(II) > Fe(III) > Co(II) > Mn(II)。该试剂对Ca、Al、Cr(III)、Mg、Li等其他金属离子的萃取能力较弱。 Ni(II)的萃取与水溶液中Cl浓度呈正相关，表明Cl是Ni(II)萃取的驱动力。用水反萃取负载 Ni(II) 的有机相，在负载反萃液中以 15:1 的 O/A 比获得约 50 g/L 的 Ni(II)。利用晶体结构分析、FT-IR 光谱和最大负载量进一步研究了 Ni(II) 的萃取机理。结果表明，通过 Ni(II) 萃取形成 Ni(MEH3)Cl 络合物。综上所述，MEH3系统可以在不消耗碱性试剂的情况下从氯化物溶液中选择性萃取Ni(II)，且不产生新物质，有利于实现母液循环利用，对清洁湿法冶金产生积极影响。