Alkaline leaching of zinc from stainless steel Electric Arc Furnace dusts
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Aalto University
Anna Stefanova   

Aalto University, Vuorimiehentie 2, PO Box 16200, FI-00076 Espoo, Finland
Publication date: 2014-09-01
Physicochem. Probl. Miner. Process. 2015;51(1):293–302
Stainless steel production generates dust and sludge that are considered as harmful waste. These dusts contain also valuable metals but the extraction and recovery of valuables is difficult due their complex composition. Zinc is the most troublesome element in the dust and it hinders the direct recycling of dust back into furnaces. In this paper two different stainless steel electric arc furnace dusts (EAF1 and EAF2), from Outokumpu Stainless (Tornio, Finland), were leached using NaOH solutions. The purpose was selectively leach zinc out from the dusts and find factors that affected most the dissolution of zinc. Of the studied leaching factors temperature, agitation speed and NaOH concentration were found to be statistically strongly significant whereas liquid-solid ratio and bubbling gas were only somewhat significant. Two experiments from the test series gave clearly higher zinc extractions (around 60% for EAF1 and around 30% for EAF2) than the others. In both, strong 8 M NaOH solution with high temperature and agitation speed was used but the bubbling gas and liquid to solid ratio changed. Zinc was leached selectively and practically no iron, chromium and nickel dissolved.