Abstract
The efficacy of monosodium glutamate (MSG) as a lixiviant for the selective and sustainable leaching of zinc and copper from electric arc furnace dust was tested. Batch leaching studies and XRD, XRF and SEM-EDS characterization confirmed the high leaching efficiency of zinc (reaching 99%) and copper (reaching 86%) leaving behind Fe, Al, Ca and Mg in the leaching residue. The separation factor (concentration ratio in pregnant leach solution) between zinc vs. other elements, and copper vs. other elements in the optimum condition could reach 11,700 and 250 times, respectively. The optimum conditions for the leaching scheme were pH 9, MSG concentration 1 M and pulp density 50 g/L. Kinetic studies (leaching time and temperature) revealed that the saturation value of leaching efficiency was attained within 2 h for zinc and 4 h for copper. Modeling of the kinetic experimental data indicated that the role of temperature on the leaching process was minor. The study also demonstrated the possibility of MSG recycling from pregnant leach solutions by precipitation as glutamic acid (>90% recovery).
Highlights
The demand for base metals such as zinc (Zn) and copper (Cu) has increased in recent years.Natural resources of both metals are dominated by sulfide ores, which have declined both in quantity and grade causing discrepancies between supply and demand [1]
electric arc furnace (EAF) dust characterization using XRD showed the mineral phase composition was dominated by zinc oxide (ZnO)
XRD of the dust residue obtained after leaching revealed the phases were dominated by spinel (Mg-Al oxide), calcium aluminum oxide and zinc oxide phases (Figure 2)
Summary
The demand for base metals such as zinc (Zn) and copper (Cu) has increased in recent years. Natural (primary) resources of both metals are dominated by sulfide ores, which have declined both in quantity and grade causing discrepancies between supply and demand [1]. This in turn encourages the exploration of new resources, which includes primary resources and secondary ones through recycling. One of the secondary resources of base metal, which holds potential for further processing, is electric arc furnace (EAF) dust. The dust is a waste of steel making and is classified as hazardous [2]. The amount of dust produced during steel making is significant, where 11–20 kg of dust is generated for each ton of steel produced [3]
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