Researchers can isolate magnesium feedstocks from the ocean, essential for renewable vitality purposes. Credit score: Cortland Johnson | Pacific Northwest Nationwide Laboratory
Magnesium salt is extracted from Sequim seawater utilizing a novel flow-based method.
Folks have been utilizing salts from the ocean, like desk salt, since prehistoric instances. Whereas desk salt is essentially 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 all these minerals that’s ample within the sea and is turning into increasingly helpful on land.
Magnesium has rising makes use of in sustainability, equivalent 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 america to supply magnesium. The Division of Vitality included magnesium on its just lately launched record of crucial supplies for home manufacturing.
The laboratory-scale stream gadget for extracting magnesium salt. Credit score: Qingpu Wang | Pacific Northwest Nationwide Laboratory
Researchers at Pacific Northwest National Laboratory (PNNL) and the University of Washington (UW) have found a easy methodology to separate a pure magnesium salt, a feedstock for magnesium metallic, from seawater. Their findings are detailed in an paper that was just lately revealed within the journal Environmental Science & Know-how Letters. Their progressive strategy flows two options side-by-side in an extended stream. The method, referred to as the laminar coflow strategy, makes use of the boundary that’s constantly reacting on account of the flowing options. The system by no means achieves equilibrium since new options are at all times being launched.
This methodology performs a brand new trick with an outdated course of.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 referred to as lye. The ensuing magnesium hydroxide salt, which provides the antacid milk of magnesia its title, was then processed to make magnesium metallic. Nonetheless, the method ends in a fancy combination of magnesium and calcium salts, that are exhausting and expensive to separate. This current work produces pure magnesium salt, enabling extra environment friendly processing.
“Usually, individuals transfer separations analysis ahead by growing extra difficult supplies,” mentioned 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 very totally different strategy. We discovered a easy course of that works. When scaled, this course of might assist drive the renaissance of U.S. magnesium manufacturing by producing major 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 stable salt
Subban and the workforce examined their new methodology utilizing seawater from the PNNL-Sequim campus, permitting the researchers to benefit from PNNL amenities 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,” mentioned 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 methodology, the researchers stream seawater alongside an answer with hydroxide. The magnesium-containing seawater rapidly reacts to type a layer of stable 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,” mentioned PNNL postdoctoral researcher Qingpu Wang. “The preliminary stable magnesium hydroxide barrier prevents calcium from interacting with the hydroxide. We are able to selectively produce pure stable magnesium hydroxide without having extra 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 will be generated on-site utilizing seawater and marine renewable vitality. Eradicating magnesium is a crucial pre-treatment for seawater desalination. Coupling the brand new course of with current applied sciences might 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 methodology for selective separations. This new strategy has many extra potential purposes, however extra work must be executed to know the underlying chemistry of the method. The information hole affords new potentialities and analysis instructions for powering the blue economic system.
“We wish to take this work from the empirical to the predictive,” mentioned PNNL supplies scientist Elias Nakouzi. “There may be 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 vitality supplies and reaching selective separation of hard-to-separate ions for water remedy 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 Might 2022, Environmental Science & Know-how Letters.
DOI: 10.1021/acs.estlett.2c00229
The revealed research was supported by the PNNL Laboratory Directed Analysis and Growth program. Elisabeth Ryan of UW was additionally a co-author of the research. The present improvement of this expertise is supported by the Division of Vitality, Workplace of Vitality Effectivity and Renewable Vitality, Water Energy Applied sciences Workplace beneath the Marine Vitality Seedlings Program.