Carbonate formation on ophiolitic rocks at different pH, salinity and particle size conditions in CO2-sparged suspensions

Mineral carbonation is a promising CO2 sequestration strategy that offers a long-lasting and environmentally safe solution. In this study, the effect of pH, salinity and particle size in the mineral carbonation process was investigated. Ultramafic–mafic rock samples were collected from different ophiolite rock sampling sites in Luzon Island, Philippines, and these were used in mineral carbonation reaction. Dissolution experiments were conducted by exposing powdered rock samples in suspensions sparged with CO2 for 60 days at ambient conditions (25 ◦C and 1 bar). Carbonation reactions were observed at various pH conditions (4, 6, and 10) and particle sizes (62–125 and 250–420 lm). In separate experiments, the effects of pH and salinity were studied in experimental set-ups containing 5 % MgCl2 maintained at low and high pH. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to monitor concentrations of metals that could participate in the mineralization reaction (Mg, Al, Ca, and Fe) during exposure to CO2. X-ray diffraction (XRD) analysis was used to confirm the formation of carbonate minerals. Results indicate an enhancement in the carbonation process upon varying pH and salinity of the system, while there is a negligible difference in the mineral carbonation reaction at the range of particle sizes used in this study.