Electrochemical (co)deposition of lanthanum and cobalt from trimethyl phosphate-based solutions

Understanding the process of lanthanide (co)deposition is an important step towards the possibility of their efficient recycling and the electrochemical formation of lanthanide-based materials. Growing interest in organic ionic systems such as ionic liquids is due to their excellent physicochemical properties, particularly nonvolatility, thermal and electrochemical stability. In addition, organic ionic systems can be used for the extraction of lanthanides. Thus, the combined process of extraction and electrodeposition has good prospects to practical purposes. In this work, we investigated the electrochemical (co)deposition of lanthanum and cobalt from trimethyl phosphate (TMP)-based solutions. It was shown that during cathodic polarization of a Pt electrode in a solution of Co(II) in TMP, a granular deposit of Co is formed, while no deposition of La was observed in a solution of La(III) in TMP. Nevertheless, voltammetric, microscopic, and elemental analysis data indicate that electrochemical codeposition of Co and La occurs in a solution containing both La(III) and Co(II). It is concluded that the presence of Co(II) in TMP induces the electroreduction of La(III) ions.

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