Recent study discovers Iron minerals’ hidden chemistry

Recent study discovers the hidden chemistry of Iron minerals on how soils trap carbon.

A new Northwestern University study now reveals exactly why these minerals are such powerful carbon traps, though all the scientists know the fact that iron oxide minerals help lock away enormous amounts of carbon, isolating it from the atmosphere. Engineers by exploring ferrihydrite which is a common iron oxide mineral discovered it works with different chemical strategies to grab carbon and lock it away.

The engineers found that the surface of ferrihydrite is not uniformly charged. Although it has an overall positive electrical charge its surface has positively and negatively charged patches resembling a nanoscale mosaic and to form strong chemical links between its surface and organic materials, ferrihydrite uses chemical bonds and hydrogen bonding, as it does not trap carbon using electrostatic attraction alone.

Iron oxide minerals turn into highly versatile carbon snatchers by these unexpected strategies capable of grabbing and holding onto many different types of organic molecules. New insights has discovered how these minerals in soils can trap carbon, preventing it from entering the atmosphere as climate-warming greenhouse gases for decades or even centuries.

Aristilde, a professor of civil and environmental engineering at Northwestern’s McCormick School of Engineering, and her team has spent years studying minerals and soil-dwelling microbes to determine the factors that cause soil to trap or release carbon. In the recent study, Aristilde's group focused on iron oxide minerals, which are linked to more than one-third of the organic carbon deposited in soils. The researchers looked specifically at ferrihydrite, a form of iron oxide mineral that is typically found around plant roots or in soils and sediments rich in organic matter.

Ultimately, the scientists discovered that chemicals attach to ferrihydrite through a variety of ways. Positively charged amino acids attached to negative patches on the ferrihydrite surface, whereas negatively charged amino acids linked to positively charged patches. Other molecules, such as ribonucleotides, are pulled to ferrihydrite by electrostatic attraction before forming considerably stronger chemical interactions with iron atoms. Sugars, which have the weakest connections, are connected to the mineral through hydrogen bonding.