Low-cost alternative for iron recovery in lateritic nickel production by using ferronickel refining slag and kiln dust for iron precipitation from acid leachate

Iron is a primary contaminant in the acid-leaching solution during lateritic nickel production. Additionally, the accumulation of pyrometallurgical tailings from conventional nickel ore processing presents a significant challenge for industrial mining operations. This study addresses these issues by utilizing ferronickel slags (refining slag and kiln dust) as alternative neutralizing agents for the precipitation and recovery of iron from sulfuric leaching solutions. A 2³ factorial orthogonal experimental design, including two central points and six axial points, was employed to investigate the effects of agent concentrations on iron precipitation and nickel co-precipitation. The results were optimized based on response surface analysis and filtration resistance parameters. Slags and precipitated materials were characterized using XRD and XRF techniques, while initial and final liquors were analyzed via ICP-OES. Due to its high CaO content (58.33 wt%), the slag exhibited a neutralizing capacity comparable to commercial calcium and sodium carbonates. Optimal concentrations of slag (5.14 %) and kiln dust (25 %) achieved approximately 80 % removal of Fe²⁺/Fe³⁺, alongside a 46 % increase in Ni²⁺ recovery from the initial leaching solution. Precipitated iron oxides can be recovered through a reduction step, followed by washing or magnetic separation.