Hydrometallurgical Recovery of Zinc from Electric Arc Furnace Dust by Using Acidic and Alkaline Leaching

Abstract

Electric arc furnace is commonly used in secondary steel making which generates dust which is hazardous waste but it also contains zinc and other valuable metals. This dust is otherwise dumped into landfills which deteriorate the quality of land due to presence of toxic metals such as lead, arsenic and cadmium. In the present research the Electric arc furnace dust was first characterized with ICPMS for elemental analysis and XRD to determine the compounds present in the dust. In the elemental analysis it was found that zinc content was found to be 12.18% and iron content was 18.54% .It was also observed that zinc is present in the form of zinc ferrite (ZnFe₂O₄) and zinc oxide (ZnO). The objective of the study was to recover zinc from the EAFD. Zinc extraction was performed using sulphuric acid in acidic media and sodium hydroxide in basic media at various temperatures and different stirring speeds. In the research in acidic media high zinc extraction of 80.48% and is observed but the presence of iron which was  observed to be 49.163% in the filtrate make this process unfit for electrowinning. Experiment on removal of iron from the acidic filtrate is also performed by precipitation by adding Ammonium hydroxide as a precipitating agent and it was observed that along with zinc, iron was also removed from the solution and the process was unable to remove iron from the solution. Therefore the whole research drifted towards caustic leaching. In experiments with caustic leaching although the zinc recovery was observed to be lesser than acidic media but iron as an impurity is found to be negligible. The process which was found to be most suitable for zinc recovery was caustic roasting and leaching of EAFD. In this process zinc recovery is found to be 70.91% and iron recovery was found 0.147%.Finally electrowinning was performed using stainless steel electrodes at 2.9V and0.8A at room temperature of 27˚C .Zinc is found to be deposited at cathode as a grey colour deposit.