Factors affecting lead jarosite formation

Abstract

The importance of lead jarosite in hydrometallurgical processing and the factors affecting its formation in both the slow addition and autoclave synthesis techniques are discussed. In the slow addition method the principal factors are the amount and rate of delivery of soluble lead to the hot ferric sulphate solution; high temperatures and good agitation are also essential to avoid the formation of PbSO 4. The key step in the autoclave synthesis process is the selective removal of residual PbSO 4 from the reaction product and methods of accomplishing this are described. The major factors affecting the autoclave synthesis of lead jarosite are the ratio of PbSO 4 Fe 3+ , acid concentration and the ionic strength of the solution. Time, temperature, degree of agitation and seeding all affect the reaction but to a lesser degree. The principal techniques identified to suppress lead jarosite formation were high acidity (> 0.3 M H 2SO 4 or the presence of substantial quantities (> 0.3 M) of other jarosite formers such as K 2SO 4. Lead jarosites containing more than 16% Pb were produced and X-ray diffraction data for such material are presented.