CO2 sequestration by pH swing mineral ca

In this study, the feasibility of pH-swing mineral carbonation based on the HCl/NH4OH system was evaluated, addressing a gap in existing research on acid/base systems utilized for CO2 sequestration. Utilizing mining waste from asbestos production in Goiás State, Brazil, experiments were conducted under atmospheric pressure and moderate temperatures for two conditions: stoichiometric (T2E) and acid excess (T2). The results demonstrated that the Fe3+ content within the mining waste acted as a catalyst due to the hydrolysis of FeCl3 in the aqueous phase, achieving a high Mg and Fe extraction efficiency of 95 ± 2% during the leaching stage across both conditions. The solid residue showed high purity SiO2 at 90 ± 1%. Furthermore, during the purification process, 91.7 ± 1.9% of iron was removed, although a loss of Mg was also noted at 13.6 ± 2.3%. The carbonation stage yielded high purity hydromagnesite in the stoichiometric condition (T2E), with a CO2 fixation efficiency of 36.7%. Conversely, in the acid excess condition (T2), excess water and CO2 led to the formation of dypingite and reduced hydromagnesite yield. Crystallization of NH4Cl in the aqueous solution indicated supersaturation following carbonation, highlighting an efficient approach for CO2 capture with the required mineral waste and acid usage ratios.