Clay may be a simple solution to tackle carbon pollution

Clay, one of Earth’s most common nanomaterials, might soon play a surprising role in reducing carbon emissions. Researchers have found a way to use this simple, abundant material to capture carbon dioxide (CO₂) directly from the air.

The scientists behind this work are from Purdue University, working in collaboration with Sandia National Laboratories. Their recently published study earned a 2024 R&D 100 Award and has a patent application underway.

The research could lead to new solutions for reducing the amount of carbon dioxide in the atmosphere, an urgent challenge in managing the global climate crisis.

Small clay particles, big potential

The Purdue University team has been studying clay minerals for more than 30 years. Over time, they’ve unraveled important details about how these tiny particles behave.

Cliff Johnston is lead researcher and professor of agronomy in the College of Agriculture and Earth, Atmospheric, and Planetary Sciences in the College of Science at Purdue University.

“Clay minerals have an exceptionally high surface area,” he said. “One tablespoon of clay has approximately the same surface area as an American football field.”

“Most of this surface area is found in the internal pores of the clay. Over decades of research, we have found that these internal pores have polar and nonpolar regions.”

Engineers can design clays that selectively absorb CO₂ by leveraging the molecule’s preference for nonpolar regions compared to water’s preference for polar regions.

The focus of the study is a group of clays called smectites, which are some of the most common nanomaterials found in nature. Their vast surface area and tiny size make them ideal candidates for environmental applications, especially for capturing gases like carbon dioxide.

Building on past experience

In previous research, the team examined how clays absorb toxic pollutants from water. “Our prior work focused on absorption of toxic organic pollutants on clay minerals from aqueous solution,” noted Johnston.

“We found that certain types of smectites have hydrophobic surfaces and can sorb significant levels of hydrophobic contaminants, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, one of the most toxic organic compounds known.”

Dioxins, often the result of combustion and industrial activities, are harmful pollutants found at many Superfund cleanup sites. The success of clay-based materials in capturing such toxins gave the researchers confidence to apply similar methods to absorb gases like carbon dioxide.

Clay’s surprising benefits

Until recently, most efforts to capture carbon dioxide focused on high-tech materials like zeolites, metal-organic frameworks, and solid amine-based sorbents. For instance, Climeworks’ Orca facility in Iceland uses amine-based technology to pull carbon dioxide from the air.

However, clay minerals were often overlooked. They seemed too ordinary. This new study changes that perspective.

The team focused on a specific type of smectite called saponite. They explored how saponite manages carbon dioxide and water vapor – both of which compete for space in the clay’s tiny pores.

Instead of heating the clay to boost its absorption ability, the researchers took a different route. They studied the effect of humidity.

The experts found that saponite has a strong attraction to carbon dioxide when humidity is low. This behavior was confirmed using advanced spectroscopic and gravimetric techniques.

This is the first time that researchers have shown how a clay mineral can absorb both carbon dioxide and water vapor at conditions close to what we experience in everyday life – ambient concentrations of carbon dioxide and room temperature.

Tackling the climate crisis

The implications of this discovery are promising. With clay being abundant and inexpensive, it could offer a scalable way to capture carbon dioxide from the air.

People could use it to cut emissions from factories or store carbon dioxide underground, keeping it out of the atmosphere long-term.

This idea isn’t just theoretical. Johnston has already written nearly 200 papers, many of which explore how soil minerals interact with pollutants and gases. This extensive background adds weight to the new findings.

In a world looking for cost-effective and scalable solutions to the climate crisis, tiny clay particles might just have a very big role to play.

The full study was published in the journal The Journal of Physical Chemistry C.

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