Recovery of iron and copper from copper tailings by coal-based direct reduction and magnetic separation

Abstract

A technique comprising coal-based direct reduction followed by magnetic separation was presented to recover iron and copper from copper slag flotation tailings. Optimal process parameters, such as reductant and additive ratios, reduction temperature, and reduction time, were experimentally determined and found to be as follows: a limestone ratio of 25%, a bitumite ratio of 30%, and reduction roasting at 1473 K for 90 min. Under these conditions, copper-bearing iron powders (CIP) with an iron content of 90.11% and copper content of 0.86%, indicating iron and copper recoveries of 87.25% and 83.44% respectively, were effectively obtained. Scanning electron microscopy and energy dispersive spectroscopy of the CIP revealed that some tiny copper particles were embedded in metal iron and some copper formed alloy with iron, which was difficult to achieve the separation of these two metals. Thus, the copper went into magnetic products by magnetic separation. Adding copper into the steel can produce weathering steel. Therefore, the CIP can be used as an inexpensive raw material for weathering steel.