Abstract
Given the shortage of zinc resource, the low utilisation efficiency of secondary zinc resource, and the crucial problem that the synchronous dissolution of zinc from different mineral phases, an activation pretreatment method merged with calcium activation and microwave heating approach was proposed to enhance the zinc leaching from complex encapsulated zinc-containing metallurgical residues (ZMR). Results indicated that under the optimal pretreatment conditions, including microwave activation temperature of 400 °C, CaO addition of 25% and activation time of 20 min, the zinc leaching rate reached 91.67%, which was 3.9% higher than that by conventional roasting pretreatment. Meanwhile, microwave heating presents excellent treatment effects, manifested by the zinc leaching rates, all exceeding that of conventional roasting under the same conditions, while the process temperature is decreased by 200 °C. In addition, XRD and SEM-EDS analysis denoted that microwave calcification pretreatment can effectively promote the transformation of the refractory zinc minerals like Zn2SiO4 and ZnFe2O4 into the easily leachable zinc oxides. The distinctive selective heating characteristics of microwave heating strengthened the dissociation of mineral inclusion, and the generated cracks increased the interfacial reaction area and further enhancing the leaching reaction of zinc from ZMR.
Highlights
Zinc (Zn) is a key transition metal with excellent wear resistance, calenderability, and corrosion resistance; thereby its applications involve anticorrosive galvanised sheet, alloy materials, battery materials, and non-ferrous metallurgy [1,2]
The previous study reported the respective utilisation of CaO activation pretreatment [15,26] or microwave heating [29,30] to process metallurgical residues and highlighted the two ways that are effective for improving the Zn leaching efficiency [15,26,29,30]
With activation temperature increasing to 400 ◦ C, the Zn leaching rate under microwave roasting reached 92.11%, which was 4.83% higher than that by conventional roasting
Summary
Zinc (Zn) is a key transition metal with excellent wear resistance, calenderability, and corrosion resistance; thereby its applications involve anticorrosive galvanised sheet, alloy materials, battery materials, and non-ferrous metallurgy [1,2]. The output of hazardous metallurgical residues is considerable and needs to be treated efficiently It is urgent and of significant and sound research value to exploit and utilise the secondary zinc resource, zinc-containing metallurgical residues (ZMR). Zinc in ZMR always presents as multi-phase, like ZnCO3 , ZnS, Zn2 SiO4 , and ZnFe2 O4 It contains the impurities of gangues (silica and aluminium), halogens (fluorine and chlorine), lead, iron, and cadmium [3]. The previous study reported the respective utilisation of CaO activation pretreatment [15,26] or microwave heating [29,30] to process metallurgical residues and highlighted the two ways that are effective for improving the Zn leaching efficiency [15,26,29,30]. Laser particle size analyser, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were employed to analyse the mechanism of this pretreatment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
