Cementation of Lead From Lead Sulfate Slurries. I. Kinetics With Zinc Precipitant

Abstract

The cementation of metallic lead from two samples of lead sulfate powders with zinc precipitant has been studied in stirred aqueous slurries. The reaction proceeded by dissolution of the lead sulfate and precipitation of the lead from solution. The kinetics were characterized by two alternative reaction profiles; in profile No. 1, the extent of reaction rose steeply during the first 15-60 min to a gently sloping incline or plateau, while in profile No. 2 the initial rise was less sharp but the reaction continued to completion at a steady rate. Profile No. 1 was observed under all conditions studied with the lead sulfate sample that had the faster dissolution rate. The other sample gave rise to profile No. 2 when the initial partial pulp density (IPPD) of lead sulfate was 100 g/l. or higher, and to mixed No. 1 and No. 2 kinetics at lower values. The rate of reaction increased with decrease in the IPPD of lead sulfate when the kinetics followed profile No. 1, whereas the reverse condition was evident when profile No. 2 was operative.