Researchers use electromechanical cell to remove copper contamination from recycled steel

Engineering researchers at the University of Toronto have designed a new way to recycle steel that addresses copper and carbon impurities, according to a report by Safa Jinje for UofT Engineering News.

The process is explained in the paper, “Electrorefining for copper tramp element removal from molten iron for green steelmaking,” published in Resources, Conservation & Recycling and authored by Jaesuk (Jay) Paeng, William Judgeand Professor Gisele Azimi.

The process uses an oxysulfide electrolyte for electrorefining to remove copper and carbon contaminants from molten steel, generating liquid iron and sulfur as byproducts.  

“The main problem with secondary steel production is that the scrap being recycled may be contaminated with other elements, including copper," Azimi tells UofT Engineering News.

“The concentration of copper adds up as you add more scrap metals to be recycled, and when it goes above 0.1 weight percentage in the final steel product, it will be detrimental to the properties of steel. Our study is the first reported instance of electrochemically removing copper from steel and reducing impurities to below alloy level.”

The researchers designed an electrochemical cell to withstand temperatures up to 1,600 C, or 2,912 F.  Within the cell, electricity flows between the negative electrode (cathode) and the positive electrode (anode) through a novel oxysulfide electrolyte designed from slag—a waste derived from steelmaking that often ends up in cement or landfills, according to the report.

The steel with the copper impurity is used as the anode in the electrochemical cell, Azimi says, and an electromotive force is applied, forcing the copper to react with the electrolyte.

“The electrolyte targets the removal of copper from the iron when we apply electricity to the cell,” Paeng adds.

“Our method can expand the secondary steel market into different industries," Paeng tells UofT Engineering News. "It has the potential to be used to create higher-grade products, such as galvanized cold-rolled coil used in the automotive sector, or steel sheets for deep drawing, used in the transport sector.”  

The team says it wants to enable the electro-refining process to remove other contaminants from steel, including tin.