Voltammetry of Lanthanide Triflate Complexes in Acetonitrile: Implications for Separations

Krysti Knoche Gupta; Nadeesha P. W. Rathuwadu; Johna Leddy

doi:10.1149/MA2025-02612851mtgabs

Lanthanides are critical materials in many advanced technologies. High purity lanthanides are useful in many applications. However, the standard potentials E 0 for reduction of lanthanide trications LN 3+ species are outside the potential windows of common electrochemical solvents. The E 0 for LN 3+ species are not well differentiated. Excluding Eu and Yb, the average E 0 for LN 3+ + 3e ⇌ LN 0 is -(2.318 ± 0.028) V vs NHE. Ligation of metal cations is known to shift standard potentials. Here, voltammetry of seven lanthanide triflates (LN = La, Pr, Nd, Sm, Gd, Dy, Yb) is demonstrated in acetonitrile at Nafion modified electrodes.[1-4] Triflate (F 3 CSO 3 - ) chelation of the LN 3+ cations shifts the standard potentials for LN(OTf) 3 into the acetonitrile solvent window. In addition, E 0 for the LN(OTf) 3 complexes are better resolved than for the E 0 for the free LN 3+ metal cations. Excluding Pr, the peak potentials for the LN(OTf) 3 range over 160 mV for the first A peak and 110 mV for the second B peak.[1,2] The separation is sufficient to facilitate separation of one lanthanide from another.[4] The Nafion films on the electrodes are thought to extract the lanthanide species to the electrode interface because the perfluorosulfonate structure is common to Nafion and triflate. In a second set of experiments, magnetic microparticles are added to the Nafion matrix. Magnetized microparticles establish magnetic gradients at the electrode surface that are known to increase electron transfer rates.[5] Voltammetry at electrodes modified with Nafion-micromagnet composites increases the electron transfer rates for the LN(OTf) 3 complexes. Under conditions where micromagnet composites are used, the formal potentials E 0’ for LN(OTf) 3 are less well differentiated.[2] Collective separation of all lanthanide species from other transition metals species is facilitated for LN(OTf) 3 complexes at magnetically modified electrodes in acetonitrile.[4]

Voltammetry of Lanthanide Triflate Complexes in Acetonitrile: Implications for Separations

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