Sulfate-activated mineral carbonation of olivine minerals with mechanisms explained by shrinking core models and by machine learning algorithm

Direct aqueous mineral carbonation of olivine minerals has been extensively investigated in the past. However, the effect of inorganic electrolytes, particularly sodium sulfate (Na₂SO₄), on mineral carbonation rate has not been investigated yet. In this work, we report experimental results on the CO₂ uptake rate of ultrafine olivine-rich rocks using Na₂SO₄ and sodium chloride (NaCl) as inorganic catalysts under hydrothermal conditions. The reaction mechanism was explained using both a shrinking core model and a machine learning model. One major and unexpected finding was that the use of Na₂SO₄ significantly increased the carbonation efficiency compared to the baseline with and without using sodium chloride (NaCl) as an inorganic electrolyte. The results showed that an increase in the carbonation kinetics in the presence of Na₂SO₄ was evident, particularly at a temperature range of 145–185 °C. At this temperature range, the reaction kinetics are predominantly governed by the product layer diffusion control mechanism. The presence of Na₂SO₄ electrolyte likely contributed to a promoted dissolution of silica and divalent ions from the hosting rocks/minerals. Results obtained from machine learning modelling confirmed that both the temperature and Na₂SO₄ additive were key parameters for mineral carbonation compared with other process variables. The present study demonstrates the catalyzing role of Na₂SO₄ in direct aqueous mineral carbonation of olivine minerals.