Interlayer-engineered MXenes for selective metal-ion capture, separation, and recovery in complex aqueous streams

초록

Selective capture of metal ions from seawater, brines, and wastewater is vital for resource supply, pollution control, and water management. Target ions such as Li+, U(VI), rare earths, Cu2+, Cr(VI), Pb2+, and Pd2+ are often present at low concentrations in complex matrices containing salts, organic matter, impurities, and variable pH. Traditional adsorbents face issues such as limited selectivity, chemical use, fouling, incomplete regeneration, and limited validation. This review critically examines interlayer-engineered MXenes, a family of twodimensional transition-metal carbides, nitrides, and carbonitrides, as tunable platforms for the selective capture, separation, detoxification, enrichment, and recovery of metal ions. Particular emphasis is placed on how surface terminations, wet-state interlayer spacing, swelling control, anti-restacking architectures, ligand functionalization, and electrochemical operation regulate ion recognition, confined transport, adsorption, electrosorption, redox-assisted capture, and voltage-controlled regeneration. The review also distinguishes removal, capture, detoxification, separation, and true recovery, highlighting the need for mass balance, elution or stripping efficiency, concentration factor, product purity, cycling stability, and real-water validation. Key challenges, including oxidation stability, fouling, scalability, matrix interference, and long-term operation, are also discussed to clarify the practical niche of MXenes in future metal-resource recovery technologies.

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