Alloy Makes Iron On The Cheap

Electrodes made of a chromium-iron alloy may reduce the energy consumption and carbon footprint of iron production. Conventional smelters use carbon (coke) to chemically reduce ores composed of iron oxides. The process releases that carbon in the form of CO₂, emitting a massive quantity of the greenhouse gas into the atmosphere. Now, Donald R. Sadoway, Lan Yin, and Antoine Allanore of Massachusetts Institute of Technology have directly separated the iron and oxygen in iron ore in a bench-scale electrolysis experiment by using an anode made of a cheap alloy of the Earth-abundant metals chromium and iron (Nature 2013, DOI: 10.1038/nature12134). Other groups have demonstrated similar metal oxide electrolysis with iridium electrodes, but that rare element is too expensive for wide use. The MIT team’s alloy anode produces higher purity iron than that made by conventional smelting methods and liberates molecular oxygen as a secondary product. The iron-smelting industry, which has a capacity of billions of metric tons per year, could reap efficiency gains from processes based on the alloy, says University of Cambridge materials chemistry professor Derek Fray in a commentary about the work. The process could also provide breathable oxygen to astronauts in space, he adds.