Engineering MXene nanochannels for water transport and desalination

Vahid Rad

doi:10.17918/00011447

Freshwater scarcity and declining source-water quality are intensifying the demand for energy-efficient desalination and water reuse technologies. Membrane-based separations offer major advantages over conventional methods, including lower energy consumption, higher efficiency, simpler operation, and reduced secondary pollution. Among emerging membrane materials, Ti₃C₂T_x MXene has attracted significant attention because of its tunable interlayer nanochannels and highly functionalized surfaces. This dissertation investigates how cation intercalation and interfacial engineering can be used to regulate transport behavior in MXene lamellar membranes. Experimental and theoretical analyses were conducted to examine the effects of intercalating K⁺, Na⁺, Li⁺, Ca²⁺, and Mg²⁺ cations, which span wide ranges of hydration diameters and binding affinities. The results demonstrate that cation chemistry systematically controls interlayer spacing, hydrogen-bond networks, water flux, and ion permeation. Furthermore, water flux exhibited a strong dependence on cation hydration-shell size and hydration enthalpy, consistent with predictions of the Hagen-Poiseuille equation. Building on these findings, a two-step interfacial engineering strategy was developed to suppress swelling and enhance ion selectivity under forward osmosis conditions. MXene nanosheets were first functionalized with vinyltriethoxysilane to introduce polymerizable vinyl groups and tailor the surface charge. Sulfonated monomers were then UV-crosslinked within the MXene nanochannels to form hydrated ion-exchange polymer networks integrated throughout the laminate structure. The resulting hybrid membranes combine the structural tunability of MXene laminates with the ion-selective characteristics of crosslinked polyelectrolytes. The optimized membrane exhibited strongly suppressed ion permeation, high salt rejection (>99.2%), stable water permeance, excellent swelling resistance, and long-term operational stability. This work establishes new design principles for engineering MXene-based nanofluidic membranes for energy-efficient desalination and advanced water purification applications.

Engineering MXene nanochannels for water transport and desalination

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Engineering MXene nanochannels for water transport and desalination

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