While carbon dioxide (CO2) in the atmosphere attracts the most attention to environmental concerns, much of that ends up in oceans, lakes, and ponds, making them more acidic and harming marine creatures. Scientists have created “nanojars” that can capture CO2 and other harmful pollutants from the water to address this.
These tiny nanojars, much smaller than the width of a human hair, are molecules comprising multiple repeating copper ion units (a pyrazole group and a hydroxide) suspended in an organic solvent. When they come across an ion with a -2 charge – which includes significant pollutants such as carbonate, arsenate, chromate, and phosphate – these molecules bind to the target, neutralizing it.
Gellert Mezei, one of the scientists working on the project, said:
We’ve shown that we can extract chromate and arsenate to below US Environmental Protection Agency-permitted levels for drinking water – really, really low levels.
Since the solvent drifts on top of the water, forming a layer on the surface, the nanojars can be easily removed from the water. Once the nanojar solvent is taken out of the water, a weak acid is added to unravel the nanojars and release the confined ions. Afterward, these can be disposed of safely or recycled into valuable products, such as fertilizer or “green” solvents.
Furthermore, these nanojars can also be customized to target different ions. For example, using one pyrazole makes for nanojars that will target whatever -2-charged ions are present, but using two joined by a propylene linker, targets sulfate more powerfully. Meanwhile, using two pyrazoles linked with ethylene binds better to carbonate, a particularly significant pollutant.
When CO2 in the air dissolves into the ocean, it forms an excess amount of bicarbonate ions, which changes the water chemistry and makes it more acidic. Ocean acidification wreaks havoc on the aquatic environment, dissolving crabs’ shells and degrading sharks’ tough skin, messing with many biological processes.
These tiny nanojars could help solve this problem as they split bicarbonate into carbonate and captures it. However, the process is still in the first stages of development, and scientists need to figure out how to scale it up for real-world applications.
Whether this process for removing carbon dioxide from water – and indirectly, the atmosphere – would be competitive with other technologies, that I don’t know yet. There are many aspects that have to be taken into account, and that’s a tricky business.
The study was presented on Aug. 25 at the American Chemical Society Fall 2021 meeting, as seen below.