Effect of ultrasound on leaching of lead from landfilled metallurgical residues.

The potential of ultrasound as a process intensification technique in the extraction of lead from a landfilled metallurgical residues is explored. The silent or non-sonicated process makes use of acidic sodium chloride as the leachate with lead leaching in the range of 45% if a three-stage process is followed. The mixture was sonicated in a batch setup manufactured in-house. The yield obtained in silent conditions at the end of 240 min was already obtained within 30 min with ultrasound, which by itself was an improvement of 8 times. The yield of the process as a whole was improved by 19-26%. The reason for this improvement was investigated with respect to the reaction kinetics. The physical effect of ultrasound on the particle size was also studied by laser diffraction analysis. Finally, the improvement when using ultrasound in a multi-stage process was studied and it was shown that yields being obtained at the end of the 3rd stage in silent conditions is already obtained in the second stage when using ultrasound with 20% more selectivity.