An accidental discovery by researchers at the University of Michigan opens new possibilities for lithium extraction from brines previously considered “low quality,” with high magnesium content.
The discovery allows for lithium separation without the need for water or energy-intensive processes, which could transform the way this key resource for the energy transition is obtained.
The problem of lithium and magnesium
- Lithium is mainly obtained from hard rock and concentrated brines, both with high environmental impact.
- Rock mining involves large earth movements and the risk of aquifer contamination.
- Brines require extensive solar evaporation ponds, with massive water and time consumption.
- Magnesium, chemically similar to lithium but with a higher charge, complicates traditional processes. In brines with a six-to-one ratio compared to lithium, separation becomes expensive and polluting.
The new method
The developed system breaks with this logic:
- It does not use electricity or external pressure.
- It is based on a negatively charged membrane, with brine on one side and pure water on the other.
- Surprisingly, lithium crosses the membrane before magnesium, contrary to what classical theory would expect.
- The phenomenon was discovered during control experiments in electrodialysis and was repeated under different conditions with consistent results.
The explanation lies in the charge balance: chlorides cross the membrane into the pure water, and lithium accompanies them to maintain electrical neutrality, while magnesium remains trapped, compensating for the negative charges of the membrane.
Environmental advantages
- Drastically reduces the need for evaporation.
- Redistributes water instead of eliminating it, reducing water consumption.
- Generates less concentrated residual brines.
- Works even with high salinities, where other technologies fail.
This approach could alleviate tensions in arid regions like the South American salt flats, where intensive water use affects communities and ecosystems.
Limitations and possible combinations
- The system does not separate lithium from other monovalent ions like sodium.
- It can be combined with selective adsorbents, shorter evaporation stages, or specific chemical reactions to precipitate lithium.
- Research is advancing towards real techno-economic analyses to define which combinations work best outside the laboratory.
Implications for the energy transition
- Allows for thinking about more distributed and local lithium extraction, less concentrated in a few iconic salt flats.
- Facilitates smaller-scale projects, with a lower water and chemical footprint.
- In the medium term, it could be integrated into industrial water circular economy strategies, where brines are considered a resource and not waste.
- In the long term, it reinforces the idea that the energy transition should avoid reproducing the extractive mistakes of the past.
The discovery by the University of Michigan does not promise miracles, but it does offer a concrete and realistic improvement for lithium extraction. By opening the door to utilizing discarded brines, it reduces environmental impacts and expands options for an essential resource in batteries and clean technologies.
