(680e) Lithium Recovery from Unconventional Water Sources

Due to the threat of climate change and other potential issues surrounding fossil fuels, developing alternative energy carriers is of paramount importance. Renewable power sources such as wind turbines and photovoltaic panels are producing an ever-larger fraction of power. One major issue with these new power sources is that they are non-dispatchable, meaning production cannot be turned up or down at will. If the produced energy could be stored, however, it could be used as is needed, rather than as it is produced. Batteries are a good choice for scalable, location-independent, short-term power storage, and could provide the load balancing necessary for integrating these power sources. Beyond power sources, electrification of vehicles is a critical part of decarbonizing the economy, requiring large numbers of batteries. Lithium-Ion batteries are the most popular, flexible, and highest energy density batteries currently commercially available. However, to meet all these needs, a large amount of lithium will be required.

Lithium is produced from two major sources. The first is through hardrock mining of various minerals which can then be separated to produce lithium. The second is through recovery from lithium-rich brines. Currently, lithium is primarily produced from these lithium brines which are mostly found in South America, in a region called the lithium triangle. Brines are pumped to the surface and left in large pools in the sun for up to a year to evaporate off excess water, thus concentrating the brine. The concentrated brine is then processed to remove the lithium. Solar evaporation ponds involve long lead times, as the concentration process typically takes a year, meaning that increasing production volumes cannot be done quickly or easily. Further, solar evaporation ponds don’t recover any water and require disposal of excess other salts present in the brines.

To overcome the limitations of conventional methods for lithium production, alternative processes which are faster and more scalable are being considered. Two such separation techniques of particular interest are ion exchange and ion intercalation. Ion exchange, a mature and widely applied technology, has already realized commercial application for lithium extraction and is gaining momentum. Lithium intercalation, though still an emerging lithium recovery technology by comparison, has shown exceptional promise in terms of ion-ion selectivity and has attracted a great deal of research attention. Another benefit of these technologies is that they can also be applied to unconventional feedwaters which may contain valuable quantities of lithium. For example, oil and gas produced water often has a high concentration of lithium; however, there are many coexisting contaminants which may complicate separation. Industrial wastewaters also may have high concentrations of lithium, particularly when the producing process involved lithium in some way. A final major unconventional feedwater source includes natural waters, such as seawater and brackish waters, which offer the benefit of being widespread but suffer from relatively low concentrations of lithium (and high concentration of competing ions such as sodium).

If these alternative technologies could be used to effectively recover lithium from unconventional feedwater sources, that would offer many important benefits, such as faster production of lithium, scalability, and less pollution. Further, by applying these techniques to unconventional feedwaters, sources of lithium can be harnessed which will allow for greater natural resource independence. Easily producible lithium will strengthen national security for any nation which may employ these technologies.

The project develops a techno-economic analysis & life cycle assessment which can be used to evaluate these alternative separation technologies for unconventional feedstocks. It establishes what the current economic viability & environmental sustainability of these technologies are, and what is necessary to make them viable and sustainable if they are not already. In this work, ion exchange and intercalation will be investigated as alternative technologies and evaluated using seawater and brackish water desalination brines as the lithium source. The results will be compared against the conventional solar evaporation ponds. This work will use lithium carbonate as the end product.

The work aims to determine the economic viability of lithium extraction by assessing the levelized cost of lithium of each extraction technology according to the different water sources. The levelized cost of lithium is a per-kilogram cost to produce lithium including both capital and operating costs. Additionally, the life cycle assessment will calculate the environmental load in the form of kilograms of CO₂-equivalents to be able to compare new technologies relative to the conventional method.

Further, these technologies will be explored to determine what technical improvements may be necessary to make the technology viable. Monte-Carlo methods will be used to explore how improving economic and technical parameters will affect the viability and sustainability of the technology. Improvements which will explored include reducing the capital cost, improving the energy efficiency, improving the selectivity, or increasing the lifetime of the technology.

The major outcome of this study is to offer technoeconomic and environmental insight on the current status of alternative lithium extraction technologies. It will provide information on what may be the most economically and environmentally sustainable technology choices for future lithium production from brines, including seawater desalination brine. Finally, it will explore the impact of technical improvements on the performance of lithium extraction technologies to determine which improvements are the most beneficial.