K-jarosite (KFe3(SO4)2(OH)6), the most common jarosite-type mineral in natural and industrial settings, has been widely studied to understand its dissolution behavior in both environmental and industrial contexts. However, reported kinetic data remain inconsistent due to the combined influence of kinetic factors, despite the importance of such data for optimizing system conditions and improving process control and environmental management. The present work aims to help elucidate K-jarosite dissolution by carrying out new experiments in sulfuric acid medium (pH 1 and 2) at different temperatures (296, 323 and 343 K) and using two initial concentrations (0.4 and 1 g of K-jarosite/kg of solution). K-jarosite was synthesized and characterized by analytical techniques (XRD, SEM and BET), and the composition was determined by induction-coupled plasma optical emission spectroscopy (ICP-OES). Derivative (DVKM), Noyes–Whitney (NWKM) and Shrinking Core (SCKM) kinetic models previously used in the literature of jarosite-type compounds were adjusted to the data obtained here and compared. The results showed that higher temperatures and lower pH led to faster dissolution rates. Smaller initial concentrations decreased the rates slightly but had less impact than the other variables. Experiments at pH 1 led to the dissolution of all jarosite solids, while at pH 2 they led to incomplete dissolution. Remarkably, at pH 2 and at higher temperatures (mainly at 343 K), there was slight reprecipitation of the iron. XRD analysis identified no peak other than K-jarosite peaks after dissolution. DVKM and NWKM represented the effect of the studied parameters well. However, only using SCKM was a kinetic equation describing the dissolution process obtained. While the behavior of the kinetic curve is well established, the model fails to correctly describe the induction period. Under extreme conditions (>323 K, pH 1), dissolution is described by a chemical reaction controlling stage and it changes to mass transport in mild conditions. As theoretically expected, the results obtained in this work give important information about the prediction of the behavior of jarosite dissolution in terrestrial environments (acid mine and acid rock drainages) and hydrometallurgical process in mild acidic conditions and high temperatures.
Buriti et al. (Thu,) studied this question.