Red Mud Can Be a Source of Climate-Friendly Steel by Reducing Oxygen From Iron Oxide [Study]

(Photo: Wikimedia Commons/Civertan)
Red Mud Can Be a Source of Climate-Friendly Steel by Reducing Oxygen From Iron Oxide [Study]

Mining for aluminum has left billions of tons of red mud. However, researchers found a way to utilize them using a simple chemical process called reduction.

Steel From Red Mud

In a new study, scientists discovered that red mud deemed a waste, can still be used to create climate-friendly steel. Yiannis Pontikes, a mechanical engineer at KU Leuven who was not involved in the study, said the result was "very promising." He, however, clarified that they had only tried the process with one type of red mud, so he didn't want to generalize the result.

Mining bauxite, a rock rich in aluminum oxide or alumina, is the first stage in manufacturing aluminum. Red mud, a waste product left over from the extraction of alumina, is highly alkaline and may also include hazardous heavy metals like cadmium.

This method produces 180 million tons of red mud annually. Dam breaks have caused devastating floods, leaving the material in reservoirs to dry. Currently, very little of the waste is processed to reduce its causticness. The residual material can be utilized as fill-in construction materials.

About 70% of the iron in red mud is coupled to oxygen to form oxides. Iron oxide reduction can eliminate oxygen by melting it and combining it with carbon. This is the conventional process for producing steel from iron oxide ore. Although this method is inexpensive and efficient, it produces carbon dioxide, a greenhouse gas, and uses a lot of fossil fuel.

Matic Jovičević-Klug and Isnaldi Souza Filho of the Max Planck Institute for Iron Research and other materials scientists have shown that hydrogen gas can reduce iron ore. Jovičević-Klug and Souza Filho have built on that advancement in the lab, melting ore in an electric arc furnace while subjecting it to a plasma of ionized hydrogen atoms.

Hydrogen gas does not remove oxygen atoms from iron as quickly as electrically charged hydrogen ions. Some steelmakers intend to test this method on iron ore using renewable energy. Following a 10-minute furnace melt of 15 grams of the mud, the researchers discovered pearl-sized spheres of almost pure iron. Souza Filho admitted that he was surprised with the results.

The primary benefit over alternative methods is that neither the iron nor the red mud that goes into the furnace needs to be processed, like roasting, which serves tons of energy. Furthermore, the carbon footprint of producing steel in an industry-sized electric furnace driven by renewable energy sources might be significantly reduced.

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What Is Red Mud and Why It's Dangerous?

Red mud includes every gangue material in the original bauxite ore, which is the foundation for successfully extracting aluminum oxide.

These mostly consist of different silicic acid compounds and oxides of iron and titanium. Iron(III) oxide, the primary ingredient of red mud, gives it its distinctive red color and may prove to be a highly lucrative resource for the production of green steel in the future.

Certain elements are extremely valuable and uncommon, while others are highly hazardous. Its high alkalinity and its poisonous heavy metals make it highly caustic and harmful to soil and living things, making its disposal difficult. This valuable but poisonous waste is one of the main issues in aluminum production.