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Iron and its alloys, particularly steel and cast iron, are fundamental to modern industries, driving an increasing demand for products derived from iron. Traditionally, the extraction of elemental iron from ore relies on energy-intensive blast furnaces, which contribute significantly to air pollution. Recently, researchers published findings in ACS Energy Letters regarding a more sustainable approach to extract iron from synthetic ores using electrochemistry. This innovative method has the potential to compete financially with traditional blast furnaces.
According to Paul Kempler, the study’s lead author, “Identifying oxides that can be converted to iron at lower temperatures is crucial for creating fully electrified steelmaking processes.”
The electrochemical ironmaking technique functions by delivering electricity through a liquid medium containing iron-based feedstocks. This method promises to greatly minimize air pollutants—such as greenhouse gases, sulfur dioxide, and particulate matter—while also demonstrating notable energy conservation. Earlier research by Kempler and his team successfully used this process to transform solutions with solid iron(III) oxide and sodium hydroxide into elemental iron at relatively low temperatures of 176 to 194 degrees Fahrenheit (80 to 90 degrees Celsius). However, challenges arose when testing natural iron ores with varying particle sizes and impurities, revealing that this low-temperature method lacked sufficient selectivity. To address these limitations, Kempler, alongside researchers Anastasiia Konovalova and Andrew Goldman, aimed to identify iron ore-like materials that could enhance the scalability of this electrochemical process.
The researchers initiated their study by synthesizing high surface area iron oxide particles characterized by internal cavities and connections, which could influence the electrochemical reactions. They also created larger micrometer-scale iron oxide particles to better parallel the structure of natural ores while ensuring minimal trace impurities like carbon and barium. A specialized cathode was developed to extract iron from a sodium hydroxide solution that contained these iron oxide particles when an electric current was introduced. The experiments demonstrated that dense iron oxides could be effectively reduced to elemental iron at a current density of 50 milliamperes per square centimeter—an intensity akin to fast-charging lithium-ion batteries. In contrast, more porous particles with greater surface areas proved to enable increased efficiency in the electrochemical production of iron compared to less porous samples modeled after the natural ore hematite.
The research team also assessed the economic feasibility of their electrochemical ironmaking method. They estimated the production cost of iron could be under $600 per metric ton (or $0.60 per kilogram) at the current densities tested, a figure which aligns closely with that of traditional ironmaking methods. Promisingly, the study indicated that significantly higher current densities—up to 600 milliamperes per square centimeter, comparable to those found in industrial electrolysis applications—could be attained using particles engineered for nanoscale porosity. However, advancements in the design of electrochemical cells and methods for increasing the porosity of iron oxide feedstocks are necessary before this technology can achieve commercial viability.
The authors acknowledge funding from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
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