K-jarosite precipitation kinetics at low-moderate temperatures: Factors affecting mechanism, formation rates, solid morphology and crystallinity

Jarosite is a mineral that holds significant importance in the metallurgical industry. For decades, the jarosite process, operating at high temperatures, has been employed to precipitate jarosite and recover Zn. Consequently, many studies have been undertaken to understand the precipitation behavior of jarosite-type compounds. More recently, the development of different hydrometallurgical processes at low temperature led to the need of comprehending the formation of jarosite under such conditions. Therefore, this work investigates the influence of various factors, such as the initial concentration ratio of reactants (K/Fe), agitation, seeding and temperature, on the precipitation rate. Additionally, XRD and SEM analyses of solid products were conducted to assess how those different conditions affect crystallinity and morphology. The experimental results at room temperature demonstrate the existence of three main steps of the precipitation reaction: an instantaneous precipitation, a dissolution and a reprecipitation. Notably, the initial concentration of the reactants and temperature were the main conditions influencing the kinetics of the precipitation and the crystallinity of the solid obtained, while agitation and seeding did not reveal a significant impact. The results and insights obtained from this research are invaluable for improving the understanding of jarosite precipitation at low and moderate temperatures (296 to 343 K) in hydrometallurgical processes.