Magnesium battle between EVs and cattle

Researchers from the Pacific Northwest National Laboratory and University of Washington have dicovered a simple way to extract what could be considered one of the most critical minerals to the United States and European Union, magnesium.

Since ancient times, Mankind has extracted salts from the ocean. While table salt is the easiest to obtain, seawater is a rich source of different minerals, and scientists have long been exploring the possibility of isolating specific minerals from its vast volume.

One such mineral, magnesium, is abundant in the sea and has become increasingly useful on land. This includes emerging sustainability-related applications such as carbon capture, low-carbon cement, and potential next-generation batteries.

These applications are bringing renewed attention to the domestic production of magnesium, which the U.S. relies on imports from countries like China for roughly 55% of its needs.

Currently, magnesium is produced in the U.S. through an energy-intensive process from salt lake brines. Seawater and natural brine accounted for about 64% of U.S. magnesium compound production last year, with the balance split between roughly six companies.

In addition to the increased demand for magnesium in the tech sector, there is a generally unknown reason why this mineral is perhaps truly critical – cows.

The roughly 94 million cows at nearly 32,000 dairy farms in the U.S. each require around 0.6 ounces of supplemented magnesium per day for optimum performance – that is a lot of magnesium.

Add that to the USGS Mineral Commodity Summary 2022 stating that the largest consumer of magnesium oxide included the quantity presumably needed for cows, as part of the total 78%, and one can begin to understand how critical this mineral is.

The battle for magnesium

While magnesium is the eighth most abundant element in nature, with it forming roughly 2.4% of the Earth's crust, it does not occur in a native state. Rather, it is found in a variety of compounds in seawater, brines, and other rocks.

It has a wide range of uses in industry and is also an important element in medicines. Often alloyed with aluminum due to its ability to lighten this already lightweight metal without negatively impacting its characteristics, magnesium is perhaps the most critical mineral of all.

For while the world has been priming itself for a new era of clean energy, the supply may become stretched too thin and impact an industry America relies on every day – dairy.

With magnesium as a metal sharing a place among the various other uses for raw magnesium compounds, due to the increasing use of it in the automotive industry and perhaps new battery technologies, the battle between car and cattle has got automakers and dairy farmers pulling their hair out over supply.

Although there are numerous methods to acquiring magnesium, it is going to take an ocean-sized effort to ensure that there is enough of this mineral for traditional dairy farms and emerging EV applications alike.

An ocean of magnesium

With the new uses of magnesium metal in clean energy and other applications competing for its continuing need to keep dairy cows healthy, Pacific Northwest National Laboratory and the University of Washington have come up with a means to efficiently extract pure magnesium salt, a feedstock for magnesium metal, from seawater.

Their new method, detailed in a paper published in the "Environmental Science & Technology Letters," flows two solutions side-by-side in a long stream. This technique, known as the laminar co-flow method, takes advantage of the fact that the flowing solutions create a constantly reacting boundary; this plays a new trick with an old process.

In the mid-20th century, chemical companies successfully created magnesium feedstock from seawater by mixing it with sodium hydroxide, commonly known as lye.

With the laminar co-flow method, the researchers flow seawater alongside a solution of hydroxide. The magnesium-containing seawater quickly reacts to form a layer of solid magnesium hydroxide. This thin layer also acts as a barrier to the solution mixing.

The resulting magnesium hydroxide salt, which gives the antacid milk of magnesia its name, was then processed to make magnesium metal. However, the process results in a complex mixture of magnesium and calcium salts, which are hard and costly to separate. This recent work produces pure magnesium salt, enabling more efficient processing.

"The flow process produces dramatically different results than simple solution mixing," said PNNL postdoctoral researcher Qingpu Wang. "This initial solid magnesium hydroxide barrier prevents calcium from interacting with the hydroxide. We can selectively produce pure solid magnesium hydroxide without needing additional purification steps."

It is the selectivity of this process that makes it particularly powerful, as generating pure magnesium without any calcium contamination allows future manufacturers to skip energy-intensive or expensive purification steps.

"Normally, people move separations research forward by developing more complicated materials," said Pacific Northwest National Laboratory chemist and University of Washington Affiliate Professor of Materials Science and Engineering Chinmayee Subban. "This work is so exciting because we're taking a completely different approach. We found a simple process that works. When scaled, this process could help drive the renaissance of U.S. magnesium production by generating primary feedstock. We're surrounded by a huge, blue, untapped resource."

Sustainable and necessary

This new and gentle process has the potential to be highly sustainable. For example, the sodium hydroxide used to extract the magnesium salt can be generated on-site using regular seawater and powered by marine renewable energy.

As removing magnesium is a necessary pre-treatment for seawater desalination, coupling this new process with existing technologies could make it easier and cheaper to turn seawater into freshwater.

The team is particularly excited about the future of the process. Their work not only demonstrated the first use of the laminar co-flow method for selective separations but has many additional potential applications. Nevertheless, more work needs to be done to understand the underlying chemistry of the process.

This new void of knowledge, however, offers many new possibilities and research directions for powering a "blue economy" or utilizing the ocean in a more efficient and sustainable way.

"We want to take this work from the empirical to the predictive," said PNNL materials scientist Elias Nakouzi. "There is an exciting opportunity to develop a fundamental understanding of how this process operates while applying it to important problems like creating new energy materials and achieving selective separation of hard-to-separate ions for water treatment and resource recovery."