Experimental solubility of FeCO3 in aqueous 3–20 wt% KCl at 25–80 °C

Abstract

FeCO3 is a mineral, present in both industrial and natural systems. While the solubility of FeCO3 is determining for CO2 storage, and driving for corrosion, it is not well understood. For the development of rigorous modelling, there is a lack of adequate experimental data under relevant conditions to model carbonated systems containing iron.In this work, the solid-liquid equilibrium (SLE) of the ternary system FeCO3-KCl-H2O was measured at atmospheric pressure at temperatures from 25 to 80 °C. The FeCO3 solubility was studied in aqueous KCl solutions from 3 to 20 wt%. 73 new solubility data points for the systems FeCO3–KCl–H2O are presented together with 73 oxidation data points. Results showed that less than 5% of FeCO3 is oxidized in the electrolyte system. The equilibrium concentration of FeCO3 was obtained after 5–10 days with the fastest equilibrium kinetics obtained at the highest temperature, 80 °C. Temperature had a minor impact on the FeCO3 solubility in aqueous KCl solutions. However, the FeCO3 solubility seemed to slightly decrease with temperature. The solubility data was fitted to a first-order rate equation with molality as driving, to obtain kinetic insights. The dissolution rate decreases as a function of KCl concentrations. In some cases, it was 75 % lower than in NaCl. A rate constant of approximately 0.2 1/day was obtained for most experiments. The FeCO3 solubility and kinetic data obtained in this work will allow for a deeper understanding and better prediction of CO2 corrosion and mineralization, suitable for CO2 storage.