Metal-Organic Frameworks


Some of today’s greatest energy efficiencies are born at the interface of water and energy conservation. A new filtering material used for desalination has introduced the possibility of efficiency gains by facilitating the removal of sodium from seawater or process brine while simultaneously extracting lithium.

Modern desalination plants typically use polymer membranes to convert seawater into fresh water. However, the process of forcing water through these membranes is energy-intensive and therefore costly. Researchers at Monash University, the Commonwealth Scientific and Industrial Research Organization, and the University of Texas at Austin have developed a more selective filtering material that can collect lithium ions from seawater while simultaneously removing the sodium. The research was published recently in Science Advances.

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Lithium is in increasing demand for battery production. As we’ve discussed previously in this blog, the soft, silvery-white metal, known for its light weight, contributes remarkable power-density in lithium-ion batteries. It is typically harvested from brine in arid regions of South America, Australia, China, and Africa.

“With lithium currently worth about $100 a pound, it could significantly offset the high cost of seawater desalination, helping produce important new supplies of freshwater for a thirsty planet,” University of Texas professor of chemical engineering Benny Freeman, a co-author of the study, told Water Deeply. “It would also work with the briny wastewater generated by oil and gas wells (known as produced water), which is now often injected back underground.”

The key to the process is MOFs, which have the largest internal surface area of any known material, according to the New Atlas. Their intricate internal structure makes them able to effectively capture, store, and release molecules.

“Produced water from shale gas fields in Texas is rich in lithium,” says Freeman. “Advanced separation materials concepts such as ours could potentially turn this wastestream into a resource recovery opportunity.”

With burgeoning markets for electric cars and lithium-ion batteries, and an increasing number of large-scale energy storage projects worldwide, researchers predict an increasing need for lithium in the future. One study from the University of Michigan projected a steady growth in demand for lithium up until the year 2100. Smithsonian Magazine reports that the global need will be an estimated 12 million and 20 million metric tons.

What are your impressions? Do you think that the concurrent extraction of sodium and lithium could offer enough resource recovery opportunities to offset desalination costs? Could the efficiencies offered by MOFs accelerate the adoption of desalination technologies? De Bug Web

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