Polish researchers have demonstrated a method for recovering nearly all available lithium from solid salt mixtures that mimic waste deposits left after lithium-rich brines are processed, offering a potential way to reduce losses of the critical battery metal.
In a study published in Angewandte Chemie International Edition scientists from the Institute of Organic Chemistry of the Polish Academy of Sciences, Cardinal Stefan Wyszyński University and Warsaw University of Technology showed that chemical compounds long used to detect sodium ions can be modified to selectively capture lithium from complex salt mixtures.
The researchers recovered about 95% of available lithium chloride from a sample designed to resemble waste salts generated during brine processing. The recovered material contained approximately 95% lithium chloride.
Lithium is a key component of lithium-ion batteries used in smartphones, laptops, electric vehicles and energy storage systems. Demand for the metal is expected to increase as countries expand renewable energy generation and electrify transport.
Current lithium production methods are often energy-intensive and environmentally demanding. Lithium is primarily obtained either from hard-rock deposits, which require high-temperature processing and chemical treatment, or from natural brines, where extraction commonly relies on months of evaporation in large ponds.
Conventional brine processing can leave substantial amounts of lithium behind. Researchers said only about half of the lithium is often recovered, with the remainder ending up in solid salt residues that are typically discarded.
Recovering lithium from such waste streams could improve resource efficiency, reduce pressure for new mining projects and lower raw material losses.
One of the main challenges is that lithium is present alongside much larger quantities of sodium, potassium, magnesium and calcium. Many of their salts have similar chemical properties, making separation difficult.
The researchers addressed the problem using ionophores, molecules capable of selectively binding specific ions. While sodium ionophores have long been used in ion-selective electrodes to detect sodium, the new study found that the same molecular framework can preferentially bind lithium under appropriate conditions.
The team examined eight related compounds that shared a common chemical structure but differed in their side groups. The comparison allowed the researchers to determine how small structural modifications affected lithium binding.
For one compound, the researchers observed the formation of a stable complex consisting of one ionophore molecule and one lithium ion.
The method relies on solid-liquid extraction. A solid salt mixture is contacted with an organic liquid containing the ionophore. The selected compound transfers lithium salt into the organic phase while leaving most sodium, potassium and magnesium salts behind in the solid residue.
Researchers said the approach could potentially be applied to salt waste generated during brine processing, low-grade salt deposits and selected battery waste streams.
To test the method, the team used about 100 grams of a multi-component salt mixture designed to mimic the ionic composition of brine from the Salar de Atacama, one of the world's most important lithium-producing regions.
After two extraction cycles, nearly all available lithium chloride had been recovered. According to the study, the ionophore transferred lithium into the organic phase thousands of times more readily than sodium, potassium or magnesium, resulting in high selectivity.
Separating lithium from calcium proved more difficult, and calcium chloride remained the main impurity in the recovered product.
Researchers also highlighted the relative simplicity of the ionophore molecules. Many previously developed lithium receptors have complex structures that complicate large-scale production.
The compounds used in the study have a modular design and can be synthesized from readily available chemical building blocks. The team reported producing ionophores in batches of up to 58 grams, a scale that could support further development of the technology.
The researchers said the findings suggest that relatively simple and scalable chemical compounds could help improve lithium recovery from waste salt streams and reduce losses of a raw material considered essential for the global energy transition. (PAP)
PAP - Science in Poland
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