2026-01-09 パシフィック・ノースウェスト国立研究所（PNNL）
＜関連情報＞
- https://www.pnnl.gov/publications/local-magnetic-field-gradients-enable-critical-material-separations
- https://www.sciencedirect.com/science/article/abs/pii/S1383586625047458
局所的な磁場勾配は、イオン濃縮と重要な金属分離のための電気化学ポテンシャルの形成を加速します Localized magnetic field gradients accelerate ion enrichment and formation of electrochemical potentials for critical metal separation
Giovanna Ricchiuti, Zachary Fox, Bruce Palmer, Mohammadhasan Dinpajooh, Ivani Jayalath, Yang Huang, Shuai Zhang, Evan Mondarte, Grant E. Johnson, Alan G. Joly, Jaehun Chun, Kevin Crampton, Venkateshkumar Prabhakaran
Separation and Purification Technology Available online: 24 November 2025
DOI:https://doi.org/10.1016/j.seppur.2025.136148
Graphical abstract
Magnetic field gradients enable voltage-free, selective ion transport and interfacial enrichment of paramagnetic rare earth elements via a self-regulating drift–diffusion mechanism, leading to the selective crystallization of critical materials.
Highlights
- Local magnetic field gradients drive selective ion enrichment without applied voltage.
- Paramagnetic and diamagnetic ions exhibit opposing wave-like redistribution behavior.
- Mach–Zehnder interferometry visualizes ion transport at the magnet–liquid interface.
- Spontaneous electrochemical potentials arise from magnetically induced ion gradients.
- Enables tunable, low-energy REE crystallization for sustainable critical material recovery.
Abstract
Selective separation and crystallization are vital for recovering rare earth elements (REEs) from secondary sources like produced water, mine tailings, and coal ash. However, the near-identical chemistry of lanthanides renders conventional methods inefficient. Magnetic separation offers a compelling alternative by exploiting differences in magnetic moments, yet fields from low-cost permanent magnets are often dismissed as too weak to drive selective ion transport without chemical or electrochemical inputs. Here, we demonstrate that inhomogeneous magnetic field gradients alone, without applied electric fields, induce long-range, directed transport and spatial redistribution of solvated lanthanide ions. High-resolution Mach–Zehnder interferometry reveals the emergence of concentration waves and sustained ion enrichment, uncovering a dynamic force balance between magnetic drift and other forces in solution. These spatiotemporal observations are supported by a modified Poisson–Nernst–Planck (PNP) model that incorporates magnetic drift, standard diffusion, and charge imbalance forces. Such a magnetically driven non-equilibrium mechanism elevates near-surface concentrations to 3–4 times above bulk values, forming condensed ionic domains that not only shift the local electrochemical potential of paramagnetic species but also trigger crystallization of well-defined dysprosium oxalate crystals at the magnetized interface. These newly observed phenomena unlock a powerful, field-responsive strategy for actively sculpting interfacial energetics, expanding beyond traditional chemical functionalization and opening new avenues for controlling ionic behavior at the nanoscale. Furthermore, a conservative technoeconomic analysis suggests that these inhomogeneous field based passive magnetic separation can significantly reduce energy and chemical costs for paramagnetic REEs compared to conventional methods, offering a scalable and sustainable platform for critical metal recovery from complex feedstocks.
