CO2 sequestration by pH-swing mineral carbonation based on HCl/NH4OH system using iron-rich lizardite 1T

• Published in: Journal of CO2 utilization Vol. 24; pp. 164 - 173
• Main Authors: Arce Ferrufino, Gretta Larisa Aurora, Okamoto, Sayuri, Dos Santos, Jose Carlos, de Carvalho, João Andrade, Avila, I., Romero Luna, Carlos Manuel, Gomes Soares Neto, Turibio
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-03-2018
• Subjects: Carbonates; CO2 sequestration; HCl/NH4OH system; Lizardite 1T; Mining waste; pH-swing mineral carbonation; CO2 sequestration; pH-swing mineral carbonation; Carbonates; Lizardite 1T; HCl/NH4OH system; Mining waste
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2018.01.001

•High purity hydromagnesite was formed, employing HCl and NH4OH at atmospheric pressures.•Mining waste containing octahedral Fe3+ are suitable for pH swing mineral carbonation.•A hydrolysis mechanism among Fe3+ – HCl – H2O keeps the pH acidic during leaching.•Excess H2O and CO2 promote dypingite formation and reduce hydromagnesite formation.•Crystallization of NH4Cl aqueous solution was observed at room temperature.
In pH-swing mineral carbonation, several acid/base systems has been investigated. Currently the main acid/base systems employed are HCl/NaOH and NH4HSO4/NH4OH. However, the use of a HCl/NH4OH system was not yet elucidated. This study proposes to evaluate the feasibility of a pH-swing mineral carbonation based on HCl/NH4OH system at atmospheric pressure and moderate temperatures using mining waste from asbestos production from Goiás State, Brazil (S-GO) for two conditions (i.e. stoichiometric conditions (T2E) and acid excess (T2)). Results indicated that the Fe3+ content in S-GO acted as a catalyst, due to FeCl3 hydrolysis in aqueous solutions. Thus, high Mg and Fe extraction efficiency (95 ± 2%), were achieved in the leaching stage for both conditions. The S1 solid residue was mainly SiO2 with 90 ± 1% purity content. In the purification stage 91.7 ± 1.9% of Fet were removed, however, a loss of Mg of 13.6 ± 2.3% was also detected. On the carbonation stage, high purity hydromagnesite was formed in T2E; this stage had a 85% efficiency, thus, 36.7% of CO2 was fixed. On T2, excess H2O and CO2 promoted dypingite formation and reduced hydromagnesite formation. After carbonation, the formation of crystals was observed in the NH4Cl aqueous solution at 25 °C, indicating NH4Cl supersaturation. The results of mass balance indicate that 4 ton of mineral waste will be employed for each ton of captured CO2, as well as 2.6 ton of HCl, and 4.5 ton of NH4OH. However, 1.7 ton of SiO2, 0.55 ton of iron oxides, and 2.7 ton of hydromagnesite could be produced.