The influence of impurities on the dissolution of Ca- and Sr-bearing barite at room temperature

Abstract

The reaction path in the (Ba, Sr, Ca) SO4 solid-solution aqueous-solution (SSAS) system was experimentally studied using a batch-reactor method. The effect of the impurities “fluorite” and “iron sulfides” admixed in a natural barite sample on the reaction path was followed by analyzing the aqueous solution continuously. The dissolution and precipitation of the impurity “fluorite” affected strongly the reaction path in the SSAS system, especially the Ca/Sr/Ba ratio in the aqueous solution. This influence became stronger with decreasing CaSO4 in the solid solution. The dissolution and precipitation of fluorite could hinder the CaSO4 component from dissolving into water, and reduce the release rate of SO 4 2− from the solid solution to the aqueous solution and the removing rate of Ba2+ from the aqueous solution. In the presence of fluorite and sulfides, the aqueous Ba2+ and Sr2+ concentrations were controlled by the dissolution-precipitation of the end-members BaSO4 and SrSO4, respectively; the aqueous F−, Ca2+ and SO 4 2− concentrations were controlled by the dissolution-precipitation of fluorite. The incongruent dissolution of the (Ba, Sr, Ca) SO4 solid solution caused the solid phase to become progressively more enriched in the more insoluble component (BaSO4), while the aqueous composition shifted towards the more soluble end-members (SrSO4 and CaSO4) as equilibrium was approached to.