The international group of researchers from the UK, France, and China have published their findings in Nature Water.
In a statement, co-author Professor Melanie Britton from Birmingham University said: “There is a critical demand for more sustainable processes addressing the global challenges of mineral availability and clean water supply, which lead to a circular economy.
“We believe our findings could lead to more efficient and sustainable lithium extraction, which is crucial for the batteries powering everyday devices such as smartphones, laptops, and electric vehicles.”
The new filtration membranes enable direct lithium extraction from salt-lake brines through a selective electrodialysis process that efficiently separates lithium ions from other ions present in the brine.
Research lead Dr Qilei Song from Imperial College London said: "Our research could reduce the environmental impact of lithium mining and contribute to the development of more efficient energy storage systems for renewable energy sources. There may also be applications in other areas of resource recovery, for example, critical metal recovery from wastewater, plastic and battery recycling.”
These novel filters can differentiate between ions with one electrical charge (monovalent) and those with two charges (divalent) - making them very good at separating different types of salt ion.
The membranes use sub-nanometre channels lined with special chemical groups that interact with the ions as they pass through.
PhD student Louie Lovell from Prof Britton’s team applied pulsed field gradient nuclear magnetic resonance (PFG-NMR) to characterise the water and ion diffusion in the sub-nanometre channels in the membranes.
They found that the water diffusion co-efficients strongly depend on the channel sizes and the chemical groups within the membranes. These membranes can produce very pure lithium carbonate (Li2CO3), which the team said is of good enough quality to be used in batteries.
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