Optimization of the processes of processing and disposal of zinc-containing sludge

This study investigates the thermodynamic conditions for zinc recovery from sulfate compounds present in the sludge of ferrous metallurgy. Four sludge samples from two different metallurgical plants were analyzed. Chemical and phase analysis revealed significant amounts of iron, zinc, calcium, and silicon oxides in the sludge. The chemical composition was determined using X-ray fluorescence analysis with the S4 Explorer spectrometer. The quantitative phase composition was determined via X-ray diffraction using the STADI-P device. The studies showed that zinc is present in the sludge both in sulfate and sulfide forms, indicating the complex nature of its compounds in these wastes. Zinc extraction was performed using a reductive roasting method with the addition of limestone and coke. Laboratory experiments demonstrated the high effectiveness of limestone in converting sulfide zinc into oxide form, which facili-tates subsequent reduction. Thermal analysis showed that the optimal process temperature ranges from 1100 to 1300 °C. After roasting, zinc is almost completely removed, and the iron metallization degree reaches 94%. Furthermore, the influence of mechanochemical activation (MCA) on the phase composition of the wastes from ferrous metallurgy plants was studied. It was found that increasing the pressing pressure of briquettes to 300 MPa significantly alters the phase composition and increases the proportion of free ZnO, which positively affects the efficiency of zinc extraction. The obtained results confirm the promising potential of using limestone as a reagent for processing zinc-containing sludges. This approach not only enhances the efficiency of zinc and metal extraction but also reduces the residual zinc content in waste, contributing to improved environmental conditions and reducing negative environmental impacts