PNNL course of extracts magnesium salt from seawater utilizing laminar coflow


Researchers from Pacific Northwest Nationwide Laboratory (PNNL) and the College of Washington (UW) have developed a easy technique to isolate a pure magnesium salt, a feedstock for magnesium steel, from seawater. The brand new technique flows two options side-by-side in a protracted stream. Known as the laminar coflow technique (LCM), the method takes benefit of the truth that the flowing options create a continually reacting boundary. Recent options circulation by, by no means permitting the system to achieve a steadiness.


Wang et al.

A paper on their work is revealed in Environmental Science & Expertise.

Right here, we present that the nonequilibrium circumstances in LCM achieved utilizing a microfluidics machine and by merely coinjecting a NaOH answer with seawater may end up in improved selectivity for Mg(OH)2 in contrast to in a standard bulk mixing technique. The ensuing precipitates are characterised for composition, and the method yield and purity are optimized by means of systematic variations of the response time and the focus of NaOH. That is the primary demonstration of LCM for selective separation, and as a one-step course of that doesn’t depend on novel sorbents, membranes, or exterior stimuli, it’s straightforward to scale up. LCM has the potential to be broadly related to selective separations from advanced feed streams and various chemistries, enabling extra sustainable supplies extraction and processing.

—Wang et al.

Within the mid-20th century, chemical corporations 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 identify, was then processed to make magnesium steel. Nevertheless, the method ends in a fancy combination of magnesium and calcium salts, that are laborious and dear to separate. This latest work produces pure magnesium salt, enabling extra environment friendly processing.

PNNL chemist and UW Affiliate Professor of Supplies Science and Engineering Chinmayee Subban and the group examined their new technique utilizing seawater from the PNNL-Sequim campus, permitting the researchers to make the most of PNNL amenities throughout Washington State.

Within the laminar coflow technique, seawater flows alongside an answer with hydroxide. The magnesium-containing seawater rapidly reacts to kind a layer of stable magnesium hydroxide. This skinny layer acts as a barrier to answer mixing.


The laboratory-scale circulation machine for extracting magnesium salt. ({Photograph} courtesy of Qingpu Wang | Pacific Northwest Nationwide Laboratory)

The selectivity of this course of makes it significantly highly effective. Producing pure magnesium hydroxide, with none calcium contamination, permits researchers to skip energy-intensive and costly purification steps.

The brand new and delicate course of has the potential to be extremely sustainable. For instance, the sodium hydroxide used to extract the magnesium salt may be generated on web site utilizing seawater and marine renewable power. Eradicating magnesium is a vital pre-treatment for seawater desalination. Coupling the brand new course of with present applied sciences might make it simpler and cheaper to show seawater into freshwater.

This new strategy has many further potential purposes, however extra work must be carried out to know the underlying chemistry of the method.

The revealed research was supported by the PNNL Laboratory Directed Analysis and Improvement program. Elisabeth Ryan of UW was additionally a co-author of the research. Present growth 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.


  • Qingpu Wang, Elias Nakouzi, Elisabeth A. Ryan, and Chinmayee V. Subban (2022) “Movement-Assisted Selective Mineral Extraction from Seawater” Environmental Science & Expertise Letters 9 (7), 645-649
    doi: 10.1021/acs.estlett.2c00229


Leave a Comment