PULLING LITHIUM FROM FRACKING WATER

AS THE USE OF ELECTRIC VEHICLES and other green energy solutions have increased, so has the demand for lithium, a metal vital to producing the high-power rechargeable batteries at the heart of these technologies. Lithium mining, however, is expensive and environmentally unfriendly. However, researchers at Virginia Tech's Department of Mining and Minerals Engineering have optimized an extraction process that would draw lithium and other critical minerals from produced water, a derivative of oil and gas production.

Produced water is injected into underground reserves to enhance recovery of petroleum products or to remove heat from the process. Until now, lower concentrations of lithium, which would need significant refinement to become battery-grade quality, and its cost per pound have discouraged more widespread produced water extraction efforts. However, by refining the process to efficiently extract lower concentrations and remove more contaminants, this research is showing potential for large-scale industrial implementation.

A MEMBRANE BOOST

Traditional methods for lithium extraction rely on evaporative brine processing and hard rock mining. In the evaporative process, workers pump high-lithium brine into large ponds for solar evaporation. As the water evaporates, the brine becomes concentrated with lithium, sodium, and other minerals. Common in South America, this method consumes vast amounts of land, water, and time. Hard rock mining involves removing large sections of earth and processing the material to separate lithium from other minerals. This energy-intensive process requires land clearing as well.

The cost- and resource-heavy nature of traditional methods makes them unsuitable for low-concentration lithium sources such as produced water. But the Virginia Tech team's breakthrough in lithium extraction from produced water offers a promising alternative.

The process to separate lithium ions from solutions relies on an ion exchange membrane enhanced by an aluminum-based adsorbent for better lithium extraction. Aluminum-based adsorbents have gained success in industrial applications due to their strength and durability across multiple cycles, allowing for repeated use while maintaining effectiveness in attracting lithium ions. This newer method works faster, uses less water, and reduces environmental impact compared to traditional approaches, making it ideal for extracting lithium from lower concentration produced water.

For its five-phase approach, the Virginia Tech team modified a lithium/aluminum layered double hydroxide (Li/Al-LDH) resin membrane by enlarging the pores to increase the surface area and adding functional groups to enhance lithium-ion attraction while preserving the structural integrity of the Li/Al-LDH.

“Chemical modification increased the material’s adsorption capacity and physical modification produced a hierarchical porous structure, which expanded surface area and pore diameter to boost adsorption further,” explained Wencai Zhang, associate professor at the Department of Mining and Minerals Engineering at Virginia Tech.

The first phase removes solid particles while retaining critical minerals. The second phase uses selective precipitation followed by further refining to produce high-purity non-lithium critical mineral products. The third phase uses an efficient resin membrane to attract and separate lithium ions from the solution. Ion exchange minimizes environmental impact, requiring less water and space compared to other lithium mining methods. Benchtop continuous lithium extraction and battery-grade lithium compound production will be carried out at Austin Elements, an industrial partner of Zhang’s team with lithium extraction and purification expertise.

In phase four, carbon mineralization is used to fix carbon dioxide and remove alkaline earth metals from the solution. Carbon dioxide is then added to bond with the minerals, forming solid carbonates, which can then be filtered out of the solution. In phase five, which is still under development, the team is aiming to reduce salinity and eliminate the remaining contaminants through Phyto-microbial treatment, using genetically modified plants with enhanced purification traits.