CO₂ sequestration using a novel Na-salts pH swing mineral carbonation process

The main drawback of the indirect pH swing carbonation processes proposed so far is linked to the large amount of energy required to recycle the chemicals used to accelerate the reactions. The dissolution and carbonation steps of an alternative mineral carbonation pH swing process that employs sodium-based salts has been studied in order to minimize energy requirements typically associated to ammonium based mineral carbonation processes. The dissolution carried out at 70°C using NaHSO⁴ gave Mg extraction efficiency comparable to that of NH4HSO4 with about 50% of Mg brought into solution as MgSO⁴. In addition, the carbonation experiments (90% efficiency) demonstrate that NaHSO4 and NaOH can be used in a combined process to mineralize CO₂. The feasibility of the other process steps and optimization of the dissolution and carbonation are discussed.