Recycling bauxite residues and electrowinning iron

Electrochem Technologies & Materials Inc. (Montreal, Canada; www.electrochem-technologies.com) produced pure electrolytic iron (99.995% Fe) using its patented FerWIN process (diagram) — a sustainable zero-carbon iron-making technology — from ferrous sulfate heptahydrate (copperas) originating from the sulfation of bauxite residues. This pilot test work involved reacting concentrated sulfuric acid with bauxite residues, from which iron, aluminum and sodium sulfates, along with gypsum, are recovered. Then, the electrowinning of iron metal was performed on the crystallized copperas. Pure electrolytic iron flakes were electrowon inside a rectangular electrolyzer with 10 ft2 of cathodes, while regenerating the concentrated sulfuric acid to be recycled upstream during sulfation. “Based on the excellent faradic current efficiency (98%), low specific-energy consumption (2.9 kWh/kg Fe) and operating expenditures ($315/m.t. of Fe), we are optimistic that combining the sulfation of bauxite residues and the electrowinning of iron could represent a possible route for neutralizing, dewatering, recycling and valorizing red mud and bauxite residues,” says Francois Cardarelli, president of Electrochem Technologies & Materials. “This…