Committee Members

• Ph.D. Advisor: Professor Zhiping Lai (KAUST, Chemistry)
• External Examiner: Professor Zhiyong Ji (Hebei University of Technology)
• Committee Chair: Professor Kuo-Wei Huang (KAUST, Chemistry)
• 4th Committee Member:  Professor Yun Hau Ng (KAUST, Chemical Engineering)
• 5th Committee Member: Xu Lu (KAUST, Chemical Engineering)

Abstract

The increasing demand for lithium has intensified interest in dilute aqueous resources such as seawater, geothermal fluids, and oilfield brines. However, the low lithium concentration and high concentrations of competing ions, particularly Mg2+, make selective lithium recovery from these resources challenging. Lithium-ion-conducting ceramic membranes offer attractive opportunities because of their selective solid-state ion-transport pathways, chemical stability, and mechanical robustness, but their practical application is limited by the high temperatures and long processing times typically required for ceramic fabrication.

This dissertation investigates advanced manufacturing strategies for lithium-ion-conducting ceramic membranes, with emphasis on reducing processing temperature and processing time while establishing the relationships among membrane structure, Li⁺ transport, and lithium-separation performance. First, a melt-processable ZIF-62 metal–organic framework glass was integrated with lithium lanthanum titanate (LLTO) to fabricate LLTO/ZIF-62 glass composite membranes at substantially reduced temperatures. Thermal and structural characterization, mechanical testing, electrochemical impedance spectroscopy, and molecular simulations were combined to elucidate the effects of composition and microstructure on ion transport. Increasing LLTO content promoted the formation of an interconnected ceramic network, with a pronounced percolation transition at approximately x = 0.3. The optimized composite exhibited high Li⁺/Mg2+ selectivity, reaching approximately 59,000 in Red Sea water, and maintained stable separation performance during 30 days of continuous operation. The membrane was further demonstrated for lithium extraction from multiple natural brines with substantially different compositions.

Second, rapid Joule heating was investigated as a complementary strategy for shortening ceramic processing time. LLTO, lithium aluminum titanium phosphate (LATP), and lithium aluminum germanium phosphate (LAGP) were rapidly processed into consolidated ceramic bodies and subsequently sliced into thin membranes using diamond-wire cutting. Structural, morphological, electrochemical, and lithium-extraction characterizations demonstrated the feasibility of producing functional lithium-ion-conducting ceramic membranes through substantially shortened thermal treatment.
Overall, this dissertation establishes complementary materials and process-engineering strategies for ceramic membrane fabrication by reducing processing temperature and time, respectively. The findings demonstrate that processing conditions, microstructure, membrane geometry, ionic transport, and separation performance should be considered as an integrated materials-engineering problem for the development of practical ceramic membranes for selective lithium recovery.