Exploiting supramolecular chemistry in metal recovery: novel zwitterionic extractants for nickel(<scp>ii</scp>) salts
作者:Nilgun Akkus、John C. Campbell、James Davidson、David K. Henderson、Hamish A. Miller、Andrew Parkin、Simon Parsons、Paul G. Plieger、Ronald M. Swart、Peter A. Tasker、Lee C. West
DOI:10.1039/b300176h
日期:——
Hexadentate tris-salicylaldimine ligands bearing ortho-N-dialkylaminomethyl substituents have been shown to function as ditopic ligands for NiSO4 or NiCl2. The incorporation of the Ni-ion into the N3O33− site templates the pendant alkylammonium groups to allow them to hydrogen bond to the attendant anion(s). Formulation as complexes of the trianionic/tricationic ligand is supported by X-ray structure determinations of solvated forms of the complexes [Ni(L)SO4] and [Ni(L)Cl]Cl, where L = tris-1,1,1-2-hydroxy-3-(piperidin-1-ylmethyl)-5-tert-butylbenzaldiminomethyl}ethane. The kerosene-soluble ligand, tris-2,2′,2″-2-hydroxy-3-(di-n-hexylaminomethyl)-5-nonylbenzaldiminomethyl}amine, functions as a good extractant for nickel salts, showing high selectivity for recovery of NiCl2 over NiSO4. This reagent can be stripped and recycled directly using aqueous ammonia or by first displacing the Ni2+ with acid and then neutralising the pendant alkylammonium groups. The acid-stripping is accompanied by hydrolytic degradation of the reagent, but in many other respects this novel class of reagent shows promise in opening up novel flowsheets for nickel recovery, based on transport of the metal salt as opposed to ion-exchange based processes.
带有正-N-二烷基氨基甲基取代基的六价三水杨醛亚胺配体已被证明可作为 NiSO4 或 NiCl2 的二价配体。将镍离子加入 N3O33- 位点可模板化悬挂的烷基铵基团,使它们能够与相应的阴离子氢键结合。[Ni(L)SO4]和[Ni(L)Cl]Cl(其中 L = 三-1,1,1-2-羟基-3-(哌啶-1-基甲基)-5-叔丁基苯甲醛二甲基}乙烷)的溶解形式的 X 射线结构测定支持了三阴离子/三阳离子配体复合物的配方。煤油溶性配体--三-2,2′,2″-2-羟基-3-(二正己胺甲基)-5-壬基苯甲醛二氨甲基}胺是一种很好的镍盐萃取剂,在回收 NiCl2 而不是 NiSO4 时具有很高的选择性。这种试剂可以直接使用氨水进行剥离和回收,也可以先用酸置换 Ni2+,然后中和悬挂的烷基铵基团。酸脱除伴随着试剂的水解降解,但在许多其他方面,这一类新型试剂显示出开辟新的镍回收流程的前景,其基础是金属盐的运输,而不是基于离子交换的工艺。