Important technologies like EV batteries, smartphones, and solar panels depend on critical minerals such as lithium and magnesiumโmost of which the U.S. imports, often from geopolitical rivals. The U.S. Government Accountability Officeโs Science & Tech Spotlight: Critical Minerals from Seawater highlights a potential domestic source: brine from seawater desalination. This waste byproduct contains high concentrations of critical minerals, and researchers have successfully extracted them using methods like membrane filtration. While promising, the approach’s scalability and economic viability are still being tested through pilot projects, including one at Oregon State University. They write:
Important technologies, including electric vehicle batteries, smartphones, and solar panels, require โcriticalโ minerals such as magnesium and lithium. But the U.S. obtains most of these minerals from foreign countries, including some adversaries. Wars, trade embargoes, or other supply disruptions could seriously affect U.S. manufacturing, energy production, the defense industrial base, and other industries. Developing domestic sources could help mitigate these risks.
- Technology advances make it possible to extract critical minerals from the brine left over from desalinating seawater.
- While researchers have successfully extracted minerals from seawater desalination brine, scalability and economic viability have not been demonstrated yet.
- Policymakers and industry face questions such as which minerals to extract and how to compare this source to other options, such as terrestrial mining and importation.
What is it?Seawater contains many dissolved minerals, including several that the U.S. government has identified as critical for national security and for economic sectors such as renewable energy and infrastructure. Although the concentration of minerals in seawater is low, the volume of water in the oceans potentially offers vast quantities of minerals for extraction.
One promising option is to extract minerals from the waste created by seawater desalination plants. These facilities remove salt and other minerals from seawater, producing fresh water to bolster municipal supplies. The process also produces brine that is traditionally considered a waste product, but has two times the mineral concentration of seawater. Researchers have successfully extracted critical minerals from this brine, demonstrating that it could be an option to reduce U.S. dependence on foreign sources.
How does it work?ย Critical minerals found in seawater desalination brine include magnesium, lithium, and gallium, which can be extracted using several different techniques. For example, one way to extract lithium is through an electrically driven separation process that uses a membrane filter. The filter enables lithium ions in the brine to pass through, while blocking other ions. The collected material is further refined to produce minerals of a quality to be processed into industry-ready material for rechargeable batteries and other products.
How mature is it?Pilot programs are underway in multiple countries, and one early project has begun full-scale operations. Specifically, the Saudi Water Authority (SWA) in Saudi Arabia reports that it has launched a facility that concentrates magnesium from seawater desalination brine. However, its output is not for industrial use but for supplementing drinking water to prevent magnesium deficiency. SWA continues to study filtration and extraction technologies to produce minerals for industrial use. Pilot programs, such as a 2-year pilot underway at Oregon State University, aim to demonstrate scalability and economic viability. Universities and private industry continue to research technologies to recover more minerals from desalination brine and to extract multiple minerals at once.
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