ACEME: Direct aqueous mineral carbonation of dunite rock

This research explores the use of serpentinized dunite (which is comprised of 61% lizardite) as a feedstock for aqueous mineral carbonation. In initial experiments, dunite was heat-activated (630°C, 4 h), adopting a procedure which is similar to that used for serpentinite to enhance their carbonation reactivity. Heat-activation converts crystalline lizardite mineral into an amorphous, reactive phase, and the carbonation of this heat-activated material resulted in a magnesite yield of 55% compared to 27% obtained with raw dunite under the same reaction conditions. The formation of silanol nests occurred during carbonation of heat-activated dunite as deduced through FTIR and TGA-MS analyses. Samples of dunite were also heat-transformed at high temperatures (800°C, 3 h) to convert lizardite into forsterite, and these samples were also studied as potential feedstocks for mineral carbonation. Heat-activated dunite was found to engender much higher magnesite yields compared to heat-transformed dunite (forsterite rich) and raw dunite. This study suggests that during heat-activation of dunite, as it is for lizardite, conditions should be maintained to avoid forsterite formation.