Mesoporous silica-amine beads from blast furnace slag for CO capture applications

Steel slag, abundantly available at a low cost and containing over 30 wt% silica, is an attractive precursor for producing high-surface-area mesoporous silica. By employing a two-stage dissolution-precipitation method using 1 M HCl and 1 M NaOH, we extracted pure SiO 2 , CaO, MgO, etc . from blast furnace slag (BFS). The water-soluble sodium silicate obtained was then used to synthesize mesoporous silica. The resulting silica had an average surface area of 100 m 2 g −1 and a pore size distribution ranging from 4 to 20 nm. The mesoporous silica powder was further formed into beads and post-functionalized with polyethyleneimine (PEI) for cyclic CO 2 capture from a mixture containing 15% CO 2 in N 2 at 75 °C. The silica-PEI bead was tested over 105 adsorption-desorption cycles, demonstrating an average CO 2 capture capacity of 1 mmol g −1 . This work presents a sustainable approach from steel slag to cost-effective mesoporous silica materials and making CO 2 capture more feasible. Designing industrial-relevant solid amine sorbents in beads/pellets/monoliths form with reduced cost and scaling up is important to improve CO 2 capture at a large scale and deploy CO 2 capture technologies worldwide.