Probing the Deep Blue for Green Resources

Ironically, the world’s largest untapped resource might be available on tap. Scientists are examining new ways to utilize water as a source of raw materials, and it could be a game changer for the renewables industry. 

 

RephiLe water purification system laboratory. Image used courtesy of Unsplash

 

New Sources of Raw Materials

Transitioning to a green economy — especially at a time when supply chains are struggling — means mining materials to build more batteries, solar panels, magnets, and other components of a renewable energy infrastructure. 

However, traditional mining can damage ecosystems and pose human health risks. Finding new sources of raw materials is crucial for advancing renewable energy safely and cleanly. 

The Earth also has vastly more water than land. Because people don’t build or farm most of it, mining water for resources leaves more land available for human development.

Researchers from the U.S. Department of Energy’s Argonne National Laboratory published a paper in March 2023 detailing methods for extracting resources from water. The publication “Material Design Strategies for Recovery of Critical Resources from Water” explains that cobalt, lithium, nickel, platinum, cerium, and palladium are economically significant minerals often in short supply. 

The authors assert that acid mine drainage, groundwater, seawater, geothermal brines, municipal water, and even industrial wastewater serve as sources of critical resources. The oceans, in particular, offer vast quantities of materials because of their size. It’s just a matter of developing the technology to mine them. 

Aquifers and geothermal brines often contain lithium, a silvery metal highly prized for its role in battery production. With many people switching to electric cars, demand for the material has skyrocketed — experts project the world will need 2.1 million tons of lithium annually by 2030. But miners haven’t been able to keep up. 

 

Groundwater, seawater, municipal water, and industrial wastewater serve as sources of critical resources. Image used courtesy of Adobe Stock

 

Extracting lithium from brine pits is already draining nearby communities in Chile and Argentina. Seawater could offer an alternative way to source the material without depleting the water people depend on. Extracting lithium from the ocean would require different technology than miners currently use in geothermal brines, but the techniques the researchers are exploring could make it possible from a technical and economic standpoint. 

 

Water Extraction Techniques

The scientists from the Argonne National Laboratory outlined several possible methods for retrieving minerals from water, including: 

1. Polymeric Membranes

Polymeric membranes — already widely used in separation industries — are one potential solution. Researchers must address the low mechanical stability, insufficient surface charge, confinement dimensions, wettability, and other undesirable metrics to make it viable for widespread use.

2. Nanomaterials

2D-material nanofiltration membranes looked promising for resource recovery from water. Researchers cited the technology’s mechanical strength, modifiable chemistry, tunable physical confinement dimension, and geometry as positive characteristics.

3. Biological Materials

Biomass from animals, plants, or biodegradable waste could act as sorbents for filtering resources out of water. The authors noted that biological material is abundant, simple to process, and breaks down in the environment. 

4. Electrodes

Applying a current to water forces ions to move toward specific electrode surfaces. By reducing cations and placing them on a cathode’s surface — or storing them on the electrode’s surface or crystal structure — and then releasing them in a small amount of clean water, scientists could recover materials from the water. 

5. Interfacial Solar Steam Generators (ISSGs)

ISSGs can simultaneously clean water and extract resources from it. They use a porous, photothermal material that converts sunlight to heat. The photothermal material floats on the water’s surface. As the ISSG forces water to evaporate, technicians can collect the evaporated water from a hydrophobic surface suspended above the device. 

 

A Promising Outlook

The Argonne National Laboratory is uniquely positioned to study the chemistry and process engineering needed to extract critical minerals from water. The lab’s recent publication offers hope for innovative solutions to one of the world’s biggest challenges — finding enough materials to go around.