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Lithium has become an extremely necessary and rather scarce metal amid the rapid development of mass production of electronic devices and batteries.
Traditionally, lithium has been extracted from mining ores. This is an expensive, complex and time-consuming process that also causes damage to the environment.
However, it is likely that most of the lithium production relies on evaporation brine from huge reservoirs under the Sun for a year or even longer. The evaporation process leaves a lithium-rich solution.
Extracting lithium from this solution requires the use of appropriate chemicals that are potentially toxic. Researchers from Imperial College London have now presented a new technology for extracting lithium from salt lakes and geothermal sources.
The scientists have created a membrane of polymers with tiny, precisely designed pores in the shape of hourglass cells that can selectively capture lithium ions from complex salt solutions. These saline solutions are rich in lithium and contain sodium, potassium, magnesium, and other ions. Traditional methods lithium extraction did not allow for effective separation of lithium ions.
During traditional lithium extraction The brine is poured into huge ponds, where the evaporation process can take months or even years. This process requires the use of large amounts of water, as well as toxic chemicals and leads to greenhouse gas emissions.
The new technology promises a significant reduction in the cost of this process, as well as a reduction in harmful emissions. The polymer membrane contains tiny nanopores that act as a molecular sieve. They are coated with groups of hydrophilic elements that help guide lithium ions through the membrane and block larger ions.
During the experiments, the membrane allowed 200 lithium ions to pass through for every magnesium ion The technology’s performance is superior to most similar membrane materials, which in most cases do not achieve an efficiency of even 10:1.
When the electrodialysis device is activated, the membrane uses an electric current to pull lithium ions through its pores, leaving magnesium and other impurities behind. In tests using simulated salt lakes, the system produced high-purity lithium carbonate suitable for use in batteries.
The polymeric materials used to create the membranes are easily soluble in common solvents and can be manufactured using existing industrial technologies.
«We are in the process of establishing a climate technology company and are looking to partner with companies that extract lithium on a large scale using brine solutions», — said the lead author of the study, Dr Qilei Song.
Global demand for lithium continues to grow amid a shift to electric vehicles and alternative energy sources Lithium extraction from brine using membranes can be a more sustainable and cost-effective alternative to traditional methods, especially if the process is carried out using renewable energy sources.
The researchers have already increased the size of their own membranes and tested them on much larger electrodialysis capacitors In one of the experiments, they managed to concentrate lithium from a mixed salt solution to more than 3 moles per liter, a level that meets the requirements for the production of high-purity lithium carbonate, a key ingredient in batteries.
This technology can be used to purify water, extract valuable metals from mining wastewater, or even copper and other important materials.
«This technology has enormous potential in a variety of commercially important areas: from energy storage to water purification and recovery of critical materials in a circular economy», — emphasizes Director of Entrepreneurship at the Department of Chemical Engineering, Imperial College London, Professor Sandro Macchiotto.
The results of the study are published in the journal Nature
Source: ZME Science