NaHCO3-promoted olivine weathering with H2 generation and CO2 sequestration in alkaline hydrothermal system

Hydration of Fe(II) bearing minerals, such as olivine ((Mg,Fe)SiO 4 ), potentially generate hydrogen (H 2 ). However, because of the low Fe(II) dissolution rate, the H 2 production rate is usually low. We have recently proposed a novel system to promote H 2 production and simultaneous CO 2 storage in hydrothermal conditions via NaHCO 3 -enhanced olivine weathering. The present study reports the role of NaHCO 3 on both H 2 production from olivine hydration and on minerals generations on laboratory experiments in CO 2 -rich (0.5 mol/L NaHCO 3 ) and CO 2 -free hydrothermal conditions at pH range of 8-11. The highest H 2 , HCOOH yields and carbonation rate reached at the CO 2 -rich experiment with lower alkaline pH at 8.25. The addition of high concentration NaHCO 3 decreased pH from 10.92 to 8.25, whereas olivine and brucite dissolutions were accelerated. Thus, more Fe(II) was released from olivine and brucite, and H 2 production was accelerated. At higher pH range, olivine dissolution was promoted, but brucite dissolution was suppressed in both CO 2 -rich and CO 2 -free conditions. This study suggests H 2 production was promoted with the presence of HCO 3 − , but not the pH variation. The consumption of Fe(II)-bearing brucite was important in enhancing H 2 production during olivine hydration process.