Silicate rock dissolution by ammonium bisulphate for pH swing mineral CO₂ sequestration

A wide range of mineral resources and different technical approaches can be employed to permanently sequester the CO2 into stable carbonates through mineral carbonation. The aim of this work was to investigate the dissolution and carbonation of olivine, pyroxene and amphibole-rich rocks using an ammonium salt pH swing mineral carbonation process. The effect of temperature (50, 70 and 100 °C) and time (5, 10, 15, 30, 60, 120, 180 min) and the dissolution kinetics were studied using a batch reactor at ambient pressure. Temperature had a direct effect on the rates of mineral dissolution reactions. The higher dissolution efficiency using olivine with particles 75–150 μm was 77% in 3 h at 100 °C, with a limitation due to product layer diffusion with apparent activation energy of 31 kJ mol− 1. The final CO2 sequestration efficiency using olivine was 70 wt.%. Besides, only about 30% of Mg was extracted from pyroxene and amphibole at 100 °C due to polymerisation of non-dissolved silica and deposition of sulphate minerals on their surface. Therefore, amphibole and pyroxene-rich rocks do not represent a resource for this process. Ammonia-based mineral carbonation could integrate geological storage where the last is not feasible and where CO2 emitters and olivine resources are closely co-located.