Recovery of Zn as ZnO from Steelmaking Waste Materials by Mechanochemical Leaching, Solvent Extraction, Precipitation, and Thermal Decomposition Route

Abstract

A large amount of electric arc furnace dust (EAFD) is produced as hazardous waste materials during steelmaking in electric arc furnace. EAFD includes a considerable amount of zinc. Recovery of Zn as ZnO from EAFD via mechanochemical leaching, solvent extraction, precipitation, and thermal decomposition route was investigated. Dissolution behavior of Zn, Fe, Mn, Si, Mg, and Ca during the mechanochemical leaching of EAFD in H 2 SO 4 solution was determined. Optimum mechanochemical leaching parameters were considered as 10 g of EAFD, 2 M H 2 SO 4 , 240 min of reaction time, ball to the dust weight ratio of 20, and rotational speed of 500 rpm. D2EHPA solution (20%, vv) was used for solvent extraction of Zn from mechanochemical leach solution. McCabe-Thiele diagrams constructed for extraction and stripping stages indicated that 95% of zinc in the leach solution was extracted in three stages at A:O = 1:1, while 97% of Zn was stripped from loaded organic phase at operating line of A:O = 4:1. ZnC 2 O 4 •2H 2 O powder was precipitated from strip solution obtained by solvent extraction by adding oxalic acid solution at pH 4. Thermal properties of ZnC 2 O 4 •2H 2 O precipitated were investigated by thermogravimetric-differential thermal analysis technique. High-purity ZnO was obtained by thermal decomposition of ZnC 2 O 4 •2H 2 O precipitated.

A New Hydrometallurgical Process for Metal Extraction from Electric Arc Furnace Dust Using Ionic Liquids

“…To determine the most effective ionic liquid and oxidant combination for the extraction of Zn, In, and Ga from EAFD, two imidazolium-based ionic liquids, [Bmim + HSO 4 − ] and [Bmim + Cl − ] (50 mL, 50% v / v ), were mixed with one of three selected oxidants, KMnO 4 (0.5 g), Fe 2 (SO 4 ) 3 (0.5 g), or 50% H 2 O 2 (1 mL) ( Figure 4 ). After conducting the experiments, it was found that [Bmim + HSO 4 − ] performed considerably better than [Bmim + Cl − ] due to the ability of [Bmim + HSO 4 − ] to act as a Brønsted acid, which allows the anionic species [HSO 4 − ] to release the associated proton [H + ] into the solution [ 16 , 17 , 18 ]. Furthermore, the sulphate [SO 4 2− ] is able to act as a better ligand (compared to Cl − ) to form a stable complex with the target metals.…”

“…Therefore, one of the main characteristics of [Bmim + HSO 4 − ] is its ability to substantially lower the leaching solution’s pH, making the solution acidic [ 16 , 17 ]. For instance, it was found that for 50% v / v [Bmim + HSO 4 − ], the pH was ~0.88, whereas for the equivalent 50% v / v [Bmim + Cl − ], the leaching solution’s pH was ~4.7.…”

“…In its pure state, [Bmim + HSO 4 − ] is very viscous (900 mPa) [ 30 ]. However, when mixed with water, there is a noticeable reduction in viscosity due to its acidic properties, as it can release protons into the aqueous phase [ 16 , 17 , 31 ]. To find the optimal concentration of [Bmim + HSO 4 − ] required for metal extraction from EAFD, specific amounts of [Bmim + HSO 4 − ] were mixed with deionised water to prepare different ionic liquid concentrations of 30, 40, 50, and 60% v / v .…”

“…The recovery of In and Ga is becoming essential due to both their relative scarcity and growing demand, especially for their use in light-emitting diodes (LEDs) and other electronic devices [ 17 ]. Theocharis et al (2021) investigated the extraction and recovery of In, Ga, Cu, Zn, and Mo from end-of-life thin-film solar panels containing CIGS (copper indium gallium selenide, CuGa 1−x In x Se 2 ).…”

“…To separate and recover Zn from a leached liquor, solvent extraction and electrowinning techniques have been applied [ 17 , 18 , 19 , 20 ]. For Fe recovery, the precipitation technique [ 21 ] is mostly used, and the solvent extraction process is used for In and Ga [ 22 , 23 ].…”