Electric arc furnace dust contains mainly ZnO, ZnFe 2 O 4 , and iron oxides. In this study, chemical composition of ZnO, ZnFe 2 O 4 , and Fe 2 O 3 and leaching kinetics of ZnO, ZnFe 2 O 4 , and Fe 2 O 3 in HNO 3 solutions were investigated. It was seen that the dissolution of ZnO is very fast, therefore the leaching kinetics of ZnO cannot be determined. Kinetic parameters and model equations were derived for the leaching of ZnFe 2 O 4 and Fe 2 O 3. Leaching kinetics of ZnFe 2 O 4 was explained by the pseudohomogeneous reaction model. Activation energy and order of HNO 3 concentration were found to be as 37.5 kJ mol −1 and 0.37, respectively. The model equation was derived as X ZnFe 2 O 4 = 1 − exp[−62.83 0.37 0 exp(−37 522∕8.314) ]. It was determined that experimental data for the leaching kinetics of Fe 2 O 3 best fit with the shrinking core model (SCM). Activation energy and order of HNO 3 concentration were found to be as 51.5 kJ mol −1 and 0.67, respectively The model equation was derived using SCM as X Fe 2 O 3 = {1 − [1 − 1181.45 0.67 o exp(− 51 545∕8.314) ] 3 } .

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.

Celestite concentrate (SrSO 4 ) was converted to SrCO 3 in solutions containing CO 3 2-, HCO 3 and NH 4 + and dissolved ammonia. The effects of stirring speed, CO 3 2concentration; temperature and particle size of SrSO 4 on the reaction rate were investigated. It was found that the conversion of SrSO 4 was increased by increasing the temperature and decreasing the particle size, while the reaction rate was decreased with increasing the CO 3 2concentration. However, the stirring speed had no effect on the reaction rate. The conversion reaction was under chemical reaction control and the shrinking core model was suitable to explain the reaction kinetics. The apparent activation energy for the conversion reaction was found to be 41.9 kJ mol -1 . The amounts of the elements in the reaction solution were determined quantitatively by inductively coupled plasma-optical emission spectrometry. The characterization of the solid reactant and product was made using the scanning electron microscopyenergy dispersive spectrometry and X-ray powder diffraction analytical techniques.

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