Researchers can isolate magnesium feedstocks from the ocean, essential for renewable power functions. Credit score: Cortland Johnson | Pacific Northwest Nationwide Laboratory
Magnesium salt is extracted from Sequim seawater utilizing a novel flow-based method.
Individuals have been utilizing salts from the ocean, like desk salt, since prehistoric occasions. Whereas desk salt is probably the most simply obtained, seawater is a wealthy provide of different minerals, and researchers are investigating which of them could also be extracted from the ocean. Magnesium is one in every of these minerals that’s plentiful within the sea and is changing into increasingly more helpful on land.
Magnesium has growing makes use of in sustainability, similar to carbon seize, low-carbon cement, and potential next-generation batteries. These makes use of are reviving curiosity in home magnesium manufacturing. At present, salt lake brines, a few of that are threatened by droughts, are utilized in an energy-intensive course of in the US to provide magnesium. The Division of Vitality included magnesium on its not too long ago launched checklist of essential supplies for home manufacturing.
The laboratory-scale stream system for extracting magnesium salt. Credit score: Qingpu Wang | Pacific Northwest Nationwide Laboratory
Researchers at Pacific Northwest Nationwide Laboratory (PNNL) and the College of Washington (UW) have found a easy technique to separate a pure magnesium salt, a feedstock for magnesium metallic, from seawater. Their findings are detailed in an paper that was not too long ago printed within the journal Environmental Science & Expertise Letters. Their progressive method flows two options side-by-side in an extended stream. The method, often known as the laminar coflow method, makes use of the boundary that’s constantly reacting because of the flowing options. The system by no means achieves equilibrium since new options are all the time being launched.
This technique performs a brand new trick with an outdated course of. Within the mid-20th century, chemical firms efficiently created magnesium feedstock from seawater by mixing it with sodium hydroxide, generally often known as lye. The ensuing magnesium hydroxide salt, which supplies the antacid milk of magnesia its title, was then processed to make magnesium metallic. Nevertheless, the method ends in a posh combination of magnesium and calcium salts, that are arduous and expensive to separate. This latest work produces pure magnesium salt, enabling extra environment friendly processing.
“Usually, individuals transfer separations analysis ahead by growing extra sophisticated supplies,” stated PNNL chemist and UW Affiliate Professor of Supplies Science and Engineering Chinmayee Subban. “This work is so thrilling as a result of we’re taking a totally totally different method. We discovered a easy course of that works. When scaled, this course of may assist drive the renaissance of U.S. magnesium manufacturing by producing main feedstock. We’re surrounded by an enormous, blue, untapped useful resource.”
Seawater from the PNNL-Sequim campus fueled this analysis undertaking. Credit score: Andrea Starr | Pacific Northwest Nationwide Laboratory
From Sequim water to strong salt
Subban and the workforce examined their new technique utilizing seawater from the PNNL-Sequim campus, permitting the researchers to benefit from PNNL services throughout Washington State.
“As a Coastal Sciences workers member, I simply referred to as a member of our Sequim chemistry workforce and requested a seawater pattern,” stated Subban. “The following day, we had a cooler delivered to our lab in Seattle. Inside, we discovered chilly packs and a bottle of chilled Sequim seawater.” This work represents the collaboration that may occur throughout PNNL’s Richland, Seattle, and Sequim campuses.
Within the laminar coflow technique, the researchers stream seawater alongside an answer with hydroxide. The magnesium-containing seawater rapidly reacts to type a layer of strong magnesium hydroxide. This skinny layer acts as a barrier to answer mixing.
“The stream course of produces dramatically totally different outcomes than easy answer mixing,” stated PNNL postdoctoral researcher Qingpu Wang. “The preliminary strong magnesium hydroxide barrier prevents calcium from interacting with the hydroxide. We will selectively produce pure strong magnesium hydroxide while not having further purification steps.”
The selectivity of this course of makes it notably highly effective. Producing pure magnesium hydroxide, with none calcium contamination, permits researchers to skip energy-intensive and costly purification steps.
Sustainability for the longer term
The brand new and mild course of has the potential to be extremely sustainable. For instance, the sodium hydroxide used to extract the magnesium salt could be generated on-site utilizing seawater and marine renewable power. Eradicating magnesium is a mandatory pre-treatment for seawater desalination. Coupling the brand new course of with current applied sciences may make it simpler and cheaper to show seawater into freshwater.
The workforce is especially enthusiastic about the way forward for the method. Their work is the primary demonstration of the laminar coflow technique for selective separations. This new method has many further potential functions, however extra work must be executed to know the underlying chemistry of the method. The information hole affords new prospects and analysis instructions for powering the blue financial system.
“We wish to take this work from the empirical to the predictive,” stated PNNL supplies scientist Elias Nakouzi. “There’s an thrilling alternative to develop a basic understanding of how this course of operates whereas making use of it to essential issues like creating new power supplies and attaining selective separation of hard-to-separate ions for water therapy and useful resource restoration.”
Reference: “Stream-Assisted Selective Mineral Extraction from Seawater” by Qingpu Wang, Elias Nakouzi, Elisabeth A. Ryan and Chinmayee V. Subban, 31 Could 2022, Environmental Science & Expertise Letters.
DOI: 10.1021/acs.estlett.2c00229
The printed examine was supported by the PNNL Laboratory Directed Analysis and Growth program. Elisabeth Ryan of UW was additionally a co-author of the examine. The present growth of this expertise is supported by the Division of Vitality, Workplace of Vitality Effectivity and Renewable Vitality, Water Energy Applied sciences Workplace below the Marine Vitality Seedlings Program.
