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Electrochemistry of neodymium in phosphonium ionic liquids: the influence of cation, water content, and mixed anions

journal contribution
posted on 01.01.2020, 00:00 authored by L Sanchez-Cupido, Jenny PringleJenny Pringle, A Siriwardana, Cristina Pozo-GonzaloCristina Pozo-Gonzalo, Maria ForsythMaria Forsyth
Electrodeposition using ionic liquids has emerged as an environmentally friendly approach to recover critical metals, such a neodymium. The investigation of ionic liquid chemistries and compositions is an important part of the move towards efficient neodymium recovery from end-of-life products that needs further research. Thus, in this paper we have investigated a series of phosphonium ionic liquids as potential electrolytic media. Anions such as bis(trifluoromethylsulfonyl)imide (TFSI), dicyanamide (DCA), and triflate (TfO) have been investigated, in combination with short- and long-alkyl-chain phosphonium cations. The work here suggests that [TFSI]- is one of the most promising anions for successful deposition of Nd and that water plays an important role. In contrast, electrochemical behaviour was significantly hindered in the case of DCA ionic liquid, most likely owing to strong coordination between [DCA]- and Nd3+. Mixtures of anions, [TfO]- and [TFSI]-, have also been investigated in this work, resulting in two reduction processes that could be related to a different deposition mechanism involving two steps, as observed in the case of dysprosium or, alternatively, different coordination environments that have distinct deposition potentials. Additionally, we investigated the influence of electrode substrates-glassy carbon and copper. Cu electrodes resulted in the largest current densities and thus were used for subsequent electrodeposition at constant potential. These findings are valuable for optimising the deposition of Nd in order to develop more efficient and inexpensive recycling technologies for rare earth metals.

History

Journal

Australian journal of chemistry

Volume

73

Issue

11

Pagination

1080 - 1087

Publisher

CSIRO Publishing

Location

Clayton, Vic.

ISSN

0004-9425

eISSN

1445-0038

Language

eng

Publication classification

C1 Refereed article in a scholarly journal