Feasibility and reaction process for recovery of Si and Pb from high‐calcium zinc extraction residue by alkali roasting

Abstract

AbstractTo explore the feasibility of Si and Pb recovery from high‐calcium zinc extraction residues via alkali roasting, NaOH molten roasting is performed and the reaction process is discussed. Under the optimal reaction conditions—residue–alkali ratio of 1:5.0, reaction time of 1.75 h, and reaction temperature of 500°C—the Si and Pb extraction ratios remained stable at 74.00% and 40.00%, respectively. The X‐ray diffraction patterns of the specimens roasted at different temperatures indicated that the main factor affecting the extraction process was the presence of Na2CaSiO4, Ca2PbO4, and quartz. Further, the phase transformations and reaction processes of Si and Pb were determined. In the final phases, the specimen roasted at 550°C included quartz, Na4SiO4, Na2CaSiO4, Ca2PbO4, and Na2SO4. The kinetics data calculated using the unreacted shrinking core model showed that the roasting process followed a mixed control mechanism with an apparent activation energy of 16.99 kJ · mol−1.