Experimental conditions and carbon sequestration significance of synthesizing dawsonite using CO₂

Mineral trapping of CO₂ is the most durable and stable form of geological storage. As a natural CO₂ tracer mineral, the formation of dawsonite is closely related to CO₂ infusion, and it also be an important carbon fixation mineral for CO₂ geological storage. The condition of massive and stable presence of dawsonite in geological background is a key issue that constrains the CO₂ mineralization capture, and is also an important influencing factor in the search for CO₂ geological burial sites. To explore the conditions for the rapid synthesis of dawsonite with CO₂, we conducted comparative experiments for three main influencing factors of temperature (100/120/140/160/180/200 ℃), pH (8.5/9/9.5/10/10.5), and reaction time (6/12 h). Based on scanning electron microscopy, X-ray diffraction analysis was conducted to clarify the optimal conditions for the synthesis of dawsonite. The experiments suggested that in the range of pH 8.5–10.5 and temperature 100–180 ℃, the products were all pure dawsonite, and the synthesis amount showed a trend of increasing and then decreasing with the increase of pH and temperature. At 200 ℃, the crystallinity of dawsonite decreased and the content of pseudo boehmite increased. The prolongation of reaction time did not have an obvious promotion effect on the quality of the products, and the prolongation of reaction time at 200 ℃ would accelerate the dissolution of dawsonite instead. Overall, 140 ℃ and pH 9.5 are the best conditions for the synthesis of dawsonite from carbon dioxide and probably the ideal conditions for geological sequestration of carbon dioxide.