CO₂ injection to granite and sandstone in experimental rock/hot water systems

Experiments were conducted using a batch type micro-autoclave over a temperature range of 100-350 °C to understand granite and sandstone reactions in hot water in the absence or presence of excess CO₂. Our experiments, for one-week duration, show that the dissolution of granite and sandstone, and the deposition of secondary minerals, is enhanced by the presence of excess CO₂. Major element concentrations of the residual solution from the batch autoclave experiments were higher for the rock (granite or sandstone)/H₂O/CO₂ system, than in the rock (granite or sandstone)/H₂O system, but the sample weight loss was lower in the rock/H₂O/CO₂ system than in the rock/H₂O system. Changes in sample weight and CO₂-gas volume content concur with the deposition of aluminium silicate and calcium-aluminosilicate secondary minerals, which indicate fixation of CO₂ in the rock. Our results suggest that it may be possible for granite and/or sandstone to 'capture' CO₂, at hydrothermal conditions, and that underground disposal may be a feasible solution to reducing atmospheric emission of CO₂.