Efficient and Selective Magneto-Electrochemical Separation of Critical Materials

Efficient separation of critical elements, including nickel (Ni), cobalt (Co), lanthanum (La), and dysprosium (Dy), is crucial for the development of advanced technologies like renewable energy systems, electric vehicles, and high-performance materials. These elements, essential for applications such as powerful magnets, lithium-ion batteries, and energy-efficient lighting, frequently occur together in mineral ores, complicating their isolation. Conventional techniques like solvent extraction and ion exchange, while widely used, are resource-intensive and environmentally unsustainable, underscoring the need for novel, sustainable separation strategies.
Electrochemical separation is sustainable because of higher efficiency and ease of integration with available energy sources. Ion transport plays a pivotal role in controlling the efficiency and selectivity of electrochemical reactions at the electrode-electrolyte interface (EEI). Traditional methods for separating and manipulating ions in electrochemical separation, such as membranes, chemical ligands, and adsorption techniques, often come with high costs, inefficiencies, and loss of selectivity over time.
Our research focused on leveraging external electric and magnetic fields to precisely control the selectivity of ion transport (transference number), heralding a shift in equilibrium ion concentration near the electrodes for selective electrodeposition or electrosorption. A flow cell with a carbon electrode was utilized to study the transport behaviors of paramagnetic metal cations such as Ni²⁺, Co²⁺, La³⁺, and Dy³⁺ in aqueous electrolytes. Electric fields enabled selective ion enrichment through Faradaic and non-Faradaic mechanisms, while magnetic fields influenced ion transport via magnetophoretic effects, driven by differences in magnetic susceptibility. The combined utilization of electric and magnetic fields facilitated selective enrichment and reduction, providing a novel approach to separating elements with overlapping chemical properties. Voltammetric techniques combined with ex-situ x-ray photoelectron spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS) are used to reveal the selectivity of electrodeposition of Ni²⁺ and Co²⁺ with applied magnetic fields. In the case of La³⁺ and Dy³⁺, voltammetric techniques combined with fluorescence and absorbance measurements are employed to determine the selectivity of ion enrichment. Advanced imaging techniques, including Scanning Electrochemical Cell Microscopy (SECCM) and Mach-Zehnder Interferometry (MZI), are employed to analyze ion transport pathways and field-induced deposition dynamics at the EEI as well as understand the interplay between concentration gradients, electric fields, and magnetic fields in driving efficient and selective ion separation. Overall, our research offers a sustainable and energy-efficient method for separating critical elements and establishes a pathway for designing next-generation separation systems for recycling battery materials and recovering rare earth elements.