Chemists have discovered a more efficient way to extract lithium from industrial waste

Chemists at the Department of Energy's Oak Ridge National Laboratory have discovered a more efficient way to extract lithium from waste fluids from mine sites, oil fields and used batteries. They demonstrated that a common mineral can absorb at least five times more lithium than has been collected using previously developed absorbent materials.

„It's a low-cost high-lithium-consumption process,” said Parnas Paranthaman, ORNL Corporate Fellow and National Inventors Fellow, who has issued 58 patents. along with Jayanthi Kumar, an ORNL materials chemist who specializes in the design, synthesis and characterization of layered materials.

„The main advantage is that it works over a wider pH range of 5 to 11 compared to other direct lithium extraction methods,” said Paranthaman. The acid-free extraction process takes place at 140°C, compared to traditional methods of roasting mined minerals at 250°C or 800 to 1000°C without acid.

The team has applied for a patent discovery.

Lithium is a lightweight metal commonly used in energy-dense and rechargeable batteries. Electric vehicles, required to achieve net-zero emissions by 2050, rely on lithium-ion batteries. Industrially, lithium is extracted from brine, rocks and clay. The ORNL discovery will help meet the growing demand for lithium by making domestic sources commercially viable.

The research reveals a way out of the status quo: a linear economy in which products are produced from mining, refining or recycling, and at the end of their life, discarded as waste. Work is moving towards a circular economy where products are kept in circulation as much as possible to reduce the consumption of virgin resources and the generation of waste.

The ORNL discovery relies on aluminum hydroxide, a mineral abundant in the Earth's crust. The scientists used aluminum hydroxide as a sorbent, a substance that takes up another substance — in this case, lithium sulfate — and holds it.

In a process called lithiation, an aluminum hydroxide powder extracts lithium ions from a solvent to form a stable layer of double hydroxide, or LDH, phase. Later in delithiation, treatment with hot water causes the LDH to drop the lithium ions and regenerate the sorbent. During recycling, the sorbent is reused to extract more lithium. „This is the basis for a circular economy,” Paranthaman said.

Research is Published in the magazine ACS application objects and interfaces. A second related paper was published simultaneously The Journal of Physical Chemistry cinvestigated the stability of delithiation under various conditions.

Aluminum hydroxide exists in four highly ordered crystalline polymorphs and one amorphous or disordered form. Form plays a major role in the performance of the sorbent.

Kumar moved to Arizona State University to work with Alexandra Navrodsky to measure the thermodynamics of chemical reactions. ORNL Corporate Fellow Bruce Moyer, a renowned expert in separation science and technology, provided insight into the kinetic experiments.

„Based on calorimetric measurements, we knew that amorphous aluminum hydroxide is the least stable form of aluminum hydroxides and thus is more reactive,” Kumar said. „This was a key to this method, which resulted in higher lithium extraction efficiency.”

Since amorphous aluminum hydroxide is the least stable in inorganic forms, it spontaneously reacts with lithium from brine leaching from waste clays. „It was only when we did the measurements that we realized that the amorphous form is way, way, way less stable. That's why it's more reactive,” Kumar said.

Kumar optimizes the process by absorbing lithium from fluids containing lithium, sodium and potassium to form LDH sulfate.

At the DOE Office of Science User Facility Nanophase Materials Sciences Center at ORNL, researchers used scanning electron microscopy to characterize the morphology of aluminum hydroxide during lithiation. It is a charged neutral layer that contains atomic vacancies or small holes. Lithium is absorbed at these sites. The size of these vacancies is the key to the selectivity of aluminum hydroxide for lithium, which is a positively charged anion or cation.

„That empty site is so small that it only fits lithium-sized cations,” Kumar said. Sodium and potassium are cations with large radii. Large cations do not fit into the vacant site. However, it is more suitable for lithium.

The choice of amorphous aluminum hydroxide for lithium results in nearly perfect performance. At one point, the process captured 37 milligrams of lithium per gram of recoverable sorbent—roughly five times more. A crystalline form of aluminum hydroxide, known as gibbsite, was previously used For lithium extraction. The first step in lithiation involves extracting 86% of the lithium in leachate or brine from mine sites or oil fields. A second pass of the leachate through an amorphous aluminum hydroxide sorbent picks up the remaining lithium. „In two steps, you can completely recover the lithium,” Paranthaman said.

Venkat Roy and Fu Zhao at Purdue University examined the lifecycle benefits of a circular economy from direct lithium extraction. They compared the ORNL process to a standard method using sodium carbonate. They found that the ORNL technology used one-third the material, one-third the energy, and subsequently produced fewer greenhouse gas emissions.

Next, the researchers want to extend the process to extract more lithium and recreate the sorbent in a specific form. Now, when the amorphous aluminum hydroxide sorbent reacts with lithium and then removes the purified lithium with hot water to regenerate the sorbent, the resulting aluminum hydroxide polymorph changes from an amorphous state to a crystalline form called bayerite.

„The bayerite form is less reactive,” Kumar said. „It takes longer to react — 18 hours — or more concentrated lithium, which reacts within 3 hours to take all the lithium out of the leach solution, as opposed to the amorphous form. We have to find a way to get back to the amorphous phase, which we know is very reactive.

Success in optimizing the new process for extraction speed and efficiency could be a game-changer for domestic lithium supply. More than half of the world's land-based lithium reserves are located in places with high concentrations of dissolved minerals, such as California's Salton Sea or oil fields in Texas and Pennsylvania.

„Domestically, we don't really have lithium production,” Paranthaman said. „Less than 2% of the lithium for production comes from North America. If we can use the new ORNL process, we have many different sources of lithium across the US. The sorbent is so good, you can use it for any brine or solutions from recycled lithium-ion batteries.

Note: Jayanthi K, Lamichane TN, Roy V, et al. An Integrated Circular Economy Model System for Direct Lithium Extraction: From Minerals to Batteries Using Aluminum Hydroxide. ACS Appl Mater Interfaces. 2023;15(50):58984-58993. doi: 10.1021/acsami.3c12070

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