Carbon Dioxide Capture Using Calcium Hydroxide Aqueous Solution as the Absorbent

Abstract

Although Ca(OH)2 aqueous solution can be effectively used as an absorbent to capture CO2, its performance with highly concentrated CO2 gas mixtures has rarely been reported. Therefore, the present paper investigates the CO2-capture performance of Ca(OH)2 aqueous solution for an about 30% CO2 gas mixture. The Ca(OH)2 concentration in the solution strongly influenced the capture performance of the absorbent. The simultaneous Ca(OH)2 dissolution and CaCO3 production in the absorbent may have substantially hindered the combination of Ca2+ with CO3 2– in suspension. Therefore, a higher Ca(OH)2 concentration in suspension further reduced the CO2 absorption capacity and produced substantially agglomerated CaCO3 with low crystallinity. In contrast, the Ca(OH)2-saturated aqueous solution had the highest absorption rate and capture ratio among the six investigated absorbents. Its calculated absorption capacity of 3.05 g of CO2 [g of Ca(OH)2]−1 L–1 was 3-fold more than that of 1% Ca(OH)2 suspension solution, which confirmed Ca(OH)2-saturated aqueous solution as the most efficient absorbent for CO2 in a Ca(OH)2 aqueous solution system.

Investigation on the Effectiveness of Aqueous Carbonated Lime in Producing an Alternative Cementitious Material

“…In the X-ray diffraction pattern, the characteristic peaks at the 2h equal to 23. Han et al 2011). Additionally, the very small peak at the 2h equal to 56.42°and 57.94°appears to be due to the calcium carbonate also (Crowley 2010).…”

“…(5)). However, the lifetime of this bicarbonate ion in the alkali medium is very small (Han et al 2011), which, therefore, reacts with the other hydroxyl ion to form a carbonate ion and water (Eq. (6)).…”

“…(6)). In fact, in this step, the hydroxyl ions are consumed to neutralize the bicarbonate ions (Han et al 2011), which in turn leads to reduce the pH of the medium. Additionally, in this step, due to the production of water, the total volume of water in the reaction system increases, which in turn reduces the OH -concentration in the per unit volume of water.…”

“…Additionally, the microstructure of the carbonated compound obtained from the four different reaction condition is observed to be a crystalline. Generally, the calcium carbonate possesses three polymorphs such as calcite (rhombohedral crystal structure), vaterite (globe or oval shaped) and aragonite (needle-shaped crystal structure) (Han et al 2011;Stutzman 1996). As evidenced by the XRD Fig.…”

“…Recently, some other processes such as the precipitated calcium carbonate formation, carbonation using brines, accelerated weathering of limestone and straightforward carbonation are also reported to consume the atmospheric CO 2 (Chen et al 2006;Huijgen and Comans 2005;Hanchen et al 2008). Additionally, the carbonation of concrete, as well as the calcium hydroxide, is also reported to reduce the atmospheric CO 2 (Galan et al 2010;Han et al 2011). Currently, some investigations have been executed to reduce the CO 2 emission during the cement production by replacing the clinker with supplementary materials such as natural pozzolans, fly ash, and slag, etc (Schrabback 2010;Criado et al 2010;Juenger et al 2011;Amato 2013;Dinakar et al 2013;Jeon et al 2015;Kotwal et al 2015;Roychand et al 2016).…”