Extraction Method Inspired by Mussels

close up photograph of green mussels with white barnacles attached to shell

Innovation

Pennsylvania State University

Image: add2007 / iStock / Some rights reserved

Capture, Absorb, or Filter Chemical Entities

Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.

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Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Chemically Assemble Metal-Based Compounds

The vast majority of biochemical assembly and break down processes––even by the most complex organisms––occur within cells. In fact, cells are able to perform hundreds, even thousands, of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, the insertion of magnesium to protoporphyrin IX in the biosynthesis pathway of chlorophyll occurs in the plastid organelle within plant cells.

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Chemically Assemble Inorganic Compounds

The vast majority of biochemical assembly and break down processes––even by the most complex organisms––occur within cells. In fact, cells are able to perform hundreds, even thousands, of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). For example, coral polyps transform dissolved calcium and carbonate ions into crystalized calcium carbonate within the calicoblastic cells.

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The mussel-inspired nanocellulose (MINC) coating from Pennsylvania State University uses negatively charged ions to pull rare earth elements from water while using little energy.

Benefits

Reduced energy
Reduced pollution

Applications

Green power generation
Electric vehicles

UN Sustainable Development Goals Addressed

Goal 6: Clean Water & Sanitation
Goal 7: Affordable & Clean Energy
Goal 9: Industry Innovation & Infrastructure

The Challenge

Similar to other rare earth elements, neodymium (Nd) is an important ingredient for powering green technologies such as wind turbines and electric vehicles that help lower our society’s environmental footprint. Paradoxically, conventional methods of extracting Nd and other rare elements from the earth consume high levels of energy that cause both air and water pollution.

Biological Model

Mussels tether themselves to underwater rocks with stringy fibers called byssal threads. Each thread has a foamy adhesive “plaque” at the end containing a mixture of s that give mussels their amazing adhesive qualities. One protein repels negatively charged ions on the surfaces of rocks, like a magnet turned the wrong way, clearing the path for another protein to latch on.

See Related Strategy

Biological Strategy

Mussels Hold On With Fancy Footwork

Common mussel

Mussel byssal threads attach to wet rocks using adhesive proteins that first prime their surfaces and then chemically bind to them.

Innovation Details

The extractive coating is composed of an array of tiny nanocrystals. The hair-like tendrils of the nanocrystals are negatively charged ions, making them highly selective towards positively charged neodymium ions. The attractive force enables the coating to pull out the rare earth element from industrial wastewater similar to how a magnet would attract iron—but without using high quantities of energy.

References

Journal article

Mussel-Inspired Nanocellulose Coating for Selective Neodymium Recovery

ACS Applied Materials and Interfaces | 2023 | Shang-Lin Yeh, Dawson Alexander, Naveen Narasimhalu, Roya Koshani, and Amir Sheikhi

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