A Nano‐Heterogeneous Membrane for Efficient Separation of Lithium from High Magnesium/Lithium Ratio Brine

Abstract

Lithium extraction from salt lake brines is highly demanded to circumvent the lithium supply shortage. However, polymer nanofiltration membranes suffer from low lithium permeability while nanofluidic devices are hindered by complicated preparation and miniaturized scales despite high permeability. Here, the authors report a facile strategy to prepare positively charged nanofiltration membranes for ultrapermeable and selective separation of lithium ions from concentrated magnesium/lithium mixtures. A new electrolyte monomer (diaminoethimidazole bromide, DAIB) containing bidentate amine groups is designed to modify pristine polyamide composite membranes. Structure characterizations and simulations show that the DAIB modification brings about nano-heterogeneity that not only improves surface hydrophilicity, but also reduces water transport resistance through the ≈100 nm thick separation layer. Water permeance of the modified membrane improves fivefold and is coupled with good stability in 200-h continuous nanofiltration. It exhibits high lithium flux (0.7 mol m −2 h −1) for brines (Mg 2+ /Li + ratio 20) at 6 bar operation pressure.

Nanofiltration Membranes Modified with a Clustered Multiquaternary Ammonium-Based Ionic Liquid for Improved Magnesium/Lithium Separation

“…Surface modification and functionalization represent an effective route to construct TFC membranes with improved membrane performance and selectivity in addition to expanding the membrane functionalities such as imparting antimicrobial and antibiofouling surface properties. Subsequently, the surface engineering of positively charged TFC membranes represents a feasible approach to economically enhance the membrane permeability of lithium without compromising its selectivity and stability . Therefore, the facile design and preparation of monomers with specific functionalities is imperative for membrane surface modification.…”

Crown Ether Grafted Graphene Oxide/Chitosan/Polyvinyl Alcohol Nanofiber Membrane for Highly Selective Adsorption and Separation of Lithium Ion

“…Salt lake brine is the main source of lithium extraction technology at present, and the common feature of salt lake lithium resources in China is the high ratio of magnesium to lithium [7]. Therefore, the development of lithium extraction and separation technology suitable for salt lake brines with high magnesium-to-lithium ratio in China has very important economic value and strategic significance [8].…”

Highly Porous Self-Supporting Graphene Oxide-Based Membranes for the Selective Separation of Lithium Ions

“…According to the theory of host–guest chemistry, the host chemical AB12C4 preferentially forms a stable host–guest complex with the guest metal Li + in a mixed ion solution because the cavity size of AB12C4 matches the size of Li + . The complex is mainly formed by the ionic bonding interaction between the negative oxygen atom on the AB12C4 ring and Li + through the coordination chelation force. , …”