CO2 Capture through Aqueous Carbonation Using Green Liquor Dregs as the Absorbent

Industrial side streams can be used to capture CO₂ due to the presence of metals such as Ca, Mg, Na, and others. Green liquor dregs (GLD), an industrial alkaline solid waste generated by pulp and paper companies, can capture CO₂ through aqueous direct carbonation. However, aqueous carbonation requires high water consumption. To address this, an alkaline wastewater from the pulp and paper industry was used as an alternative to fresh water, reducing the need for additional water consumption. In this work, the absorption capacities, reaction yield, and physicochemical characteristics of the samples were studied. A 3D-printed reactor, designed by our research group, was used to take advantage of bubble turbulence for mixing the aqueous and gaseous phases, thereby reducing electricity consumption. The solids before and after carbonation were analyzed using X-ray diffraction and scanning electron microscopy. The absorption capacity for GLD in deionized water was in the range between 5.92 and 14.86 g/L, while for GLD in wastewater, it was between 8.11 and 17.81 g/L. These results indicate that the presence of wastewater can enhance CO₂ absorption. Physicochemical analysis confirmed the presence of CaCO₃ after the reaction.

The capture of CO₂ by side streams in alkaline wastewater is a promising method for reducing CO₂ and valorizing these byproducts.