ENVIRONMENTALLY BENIGN RECOVERY OF LITHIUM AND OTHER CRITICAL MINERALS FROM A NEVADA CLAY DEPOSIT

Lithium is an essential critical mineral for clean energy technologies, such as, electric vehicles (EVs), the big batteries used to store electricity which are critical to achieve carbon neutral by 2050. According to the consulting firm McKinsey, the current global lithium supply will not meet the projected demand for large lithium-powered batteries by 2030¹. Conventional lithium hard-rock mining is still very difficult to get approved in US because of environmental burden, such as contaminating groundwater, generating large amount of acid wastes. Thus, an environmentally friendly extraction method is highly desired.

Lithium-bearing clay minerals, ~7% of total lithium production, are important alternative mineral sources². The practical methods of extraction of Li from Li-bearing clay minerals are through acidification with strong acids, salt roasting and alkalization². In this study, we tested environmentally benign extraction method utilizing different combinations of citric acid, supercritical CO₂ and magnesium sulfate salt. The Nevada clay studied in this work has ~1800 ppm lithium and 266 ppm rare earth elements (REE) including Y and Sc. It contains 68% phyllosilicates, including majority illite/smectite and small amounts of chlorite. Other minerals include 7 wt% quartz, 15% k-feldspar and 10% calcite.

Magnesium sulfate as the leaching agent has been used to recover metals from ion adsorption type REE ores^{e.g., 3,4}. Our preliminary results indicate that MgSO₄ can barely remove REE, lithium and manganese from the studied clay deposit. The same is true for only supercritical CO₂. The combination of citric acid and MgSO₄, in contrast, is very effective in removing REE (60%), lithium (40%) and Mn (>90%). Ongoing work includes testing with all three leaching agents (citric acid, magnesium sulfate and supercritical CO₂).

References

1. McKinsey Report, mckinsey.com/industries/automotive-and-assembly/our-insights/battery-2030-resilient-sustainable-and-circular.
2. Zhao et al., 2023. DOI: 10.1016/j.hydromet.2023.106025.
3. Ran et al., 2017, DOI: 10.3390/min7090152
4. Xiao et al., 2015, DOI: 10.1016/j.hydromet.2015.02.011

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This project is supported by the U.S. DOE FECM via FWP-23-025668. SAND2024-07689A