4-Phosphoryl pyrazolones for highly selective lithium separation from alkali metal ions

In this study, it is demonstrated that the 4-phosphoryl pyrazolones, H L 2 -H L 4 , in the presence of the typical industrial organophosphorus co-ligands tributylphosphine oxide (TBPO), tributylphosphate (TBP) and trioctylphosphine oxide (TOPO), are able to selectively recognise and extract lithium ions from aqueous solution. Structural investigations in solution as well as in the solid state reveal the existence of a series of multinuclear Li + complexes that include dimers (TBPO, TBP) as well as rarely observed trimers (TOPO) and represent the first clear evidence for the synergistic role of the co-ligands in the extraction process. Our findings are supported by detailed NMR, MS and extraction studies. Liquid-liquid extraction in the presence of TOPO revealed an unprecedented high Li + extraction efficiency (78%) for H L 4 compared to the use of the industrially employed acylpyrazolone H L 1 (15%) and benzoyl-1,1,1-trifluoroacetone (52%) extractants. In addition, a high selectivity for Li + over Na + , K + and Cs + under mild conditions (pH ~ 8.2) confirms that H L 2 -H L 4 represent a class of ligands that are very effective extractants for use in lithium separation.PMID:34652866 | DOI:10.1002/chem.202103640

Source: Chemistry - October 15, 2021 Category: Chemistry Authors: Jan J Weigand Jianfeng Zhang Marco Wenzel Johannes Steup Gerrit Schaper Felix Hennersdorf Hao Du Shili Zheng Leonard F Lindoy Source Type: research