Recovery of iron from electric arc furnace slag (EAFS) by the oxidative and non-oxidative leaching

A significant amount of electric arc furnace slag (EAFS) is generated as a by-product from steelmaking industry. To intensify the iron recovery from EAFS in the final product, acid leaching was carried out with both the presence and absence of oxidants. Oxidative leaching refers to the process whereby the oxidant participates in redox reactions with the metal compounds, facilitating the breakdown of the EAFS compound and promoting the dissolution of the desired metals, while non-oxidative leaching does not involve the use of an oxidant. In this study, hydrogen peroxide and potassium permanganate were used as the oxidants in leaching process. The influences of the leaching factors, such as the concentration of leaching reagent (0.5–8 M), leaching temperature (323–363 K), EAFS particle size (50–300 µm) and concentration of the oxidants (1–3 M), were also studied. The findings revealed that the particle size, acid dosage and type of oxidants significantly influenced iron recovery. Smaller particle sizes greatly improved the recovery of iron. İn the non-oxidative leaching environment, sulphuric acid exhibited a higher iron recovery compared to hydrochloric acid. The recovery efficiency was found to be 60 %. The recovery efficiency of iron for oxidative leaching in sulphuric acid was the highest at 2 M hydrogen peroxide as compared to potassium permanganate. This was because an overdose hydrogen peroxide can cause radical quenching which will reduce oxidant utilization. Oxidative leaching results in better iron recovery at optimum leaching conditions with a temperature of 50 °C, 5 M H2SO4, 1 M hydrogen peroxide, a leaching time of 120 minutes, a solid to liquid ratio of 1:20 and a stirring rate of 300 rpm. The reaction was found to follow the chemical-reaction model with chemical reaction constant of 2.04x103 min-1 and the activation energy of +16.95 kJ/mol. The cyclic voltammetry tests were conducted at potential ranges of -1.0 to 1.0 V at a scan rate of 100 mV/s using screen printed carbon electrode (SPCE). The cyclic voltammogram indicated that there were two distinct oxidation peaks to confirm that 80 °C has higher iron recovered compared to 60 °C. This study concludes that oxidative leaching environment (5 M H2SO4, 2 M H2O2, 1:20 solid to liquid ratio, 50 °C) is a promising method to recover iron as compared to non-oxidative environment. In summary, the findings in this work support the Sustainable Development Goal (SDG 12) in prioritizing on the minimization of solid waste by recycling the waste in order to reduce adverse impacts on the environment.