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Approximately 7.5 million tons of electric arc furnace dust (EAFD) are generated annually worldwide from steelmaking industry. EAFD is categorised as a hazardous waste due to the presence of heavy metals such as zinc, iron, nickel, lead and cadmium. Nevertheless, EAFD can be recycled through the extraction of zinc and iron, which constitute the greatest composition (8%-40% and 16%-60%, respectively) in EAFD. In this project, hydrometallurgical extraction of zinc and iron was performed using hydrochloric acid (HCl) as leaching agent. Factors such as temperature, acid concentration and dust-to-acid ratio on the extraction of zinc and iron were investigated. Results showed that zinc and iron extraction increased simultaneously as the temperature and acid concentration increased. The highest zinc and iron extractions were about 70% and 60%, respectively using 5 M HCl with dust-to-acid ratio of 3 g per 100 ml HCl at 70°C after 15 min of leaching. The result indicates the feasibility of zinc and iron extraction from EAFD through HCl hydrometallurgical process which will be beneficial for steelmaking industries in future.

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AbstractpH, oxidation-reduction potential (ORP) and dissolved oxygen (DO) concentration are important parameters in water quality surveillance and treatment. The changes of these parameters are associated with electron density in water. Several techniques including electrolysis and catalysis which require redox reactions and electron exchange are employed to improve these parameters. In recent years, studies reported that magnetic effects can impart considerable changes on the pH, ORP and DO concentration of water. However, the correlation between electron density and magnetic effects on these parameters has yet to be disclosed despite the fact that increased electron density in water could improve water’s reductive properties, heat capacity and hydrogen bonding characteristics. In this study, the magnetic effects on pH, ORP and DO concentration were investigated using different magnets arrangements and water flow rates based on reversed electric motor principle. Results showed that the improvement of pH, ORP and DO concentration from 5.40–5.42 to 5.58–5.62 (+ 3.5%), 392 to 365 mV (− 6.9%), and 7.30 to 7.71 mg L− 1 (+ 5.6%), respectively were achieved using combined variables of non-reversed polarity magnet arrangement (1000–1500 G magnetic strength) and water flow rate of 0.1–0.5 mL s− 1. Such decrement in ORP value also corresponded to 8.0 × 1013 number of electron generation in water. Furthermore, Raman analysis revealed that magnetic effect could strengthen the intermolecular hydrogen bonding of water molecules and favor formation of smaller water clusters. The findings of this study could contribute to potential applications in aquaculture, water quality control and treatment of cancer attributed to free radical induced-oxidative stress.