A direct conversion of blast furnace slag to a mesoporous silica–calcium oxide composite and its application in CO2 captures†
In the iron manufacturing industry, it is unavoidable to produce large volumes of blast furnace slag (BFS) as a mineral residue from the preparation of pig iron in blast furnaces as well as to discharge a high volume of carbon dioxide (CO2) gas as a result of the consumption of coke. These byproducts potentially lead to environmental problems such as ground pollution and global warming unless they are treated. BFS is a complex oxide mainly composed of CaO, MgO, SiO2 and Al2O3. The former two have the ability to react with CO2, and SiO2 is a major component of mesoporous silica (MS). Herein, we report a direct route to convert BFS into a mesoporous silica-calcium oxide composite (slagCaO-MS) possessing high CO2 adsorption performance. A composite composed of SBA-15-like mesoporous silica with a pore diameter of 12.3 nm and crystalline CaO particles (mean surface area = 128 m2 g−1) was synthesized from BFS via a facile dissolution-hydrothermal process using formic acid as a dissolving agent, while the use of mineral acids (HNO3 and HCl) resulted in the formation of ill-defined low-surface-area materials with less CO2 adsorption capacities. The composite synthesized under optimum conditions was found to have a CO2 uptake value of 18.8 wt% per mass of adsorbent, and could be regenerated for at least 10 cycles. The green and low-cost adsorbent originating from BFS with high CO2 adsorption ability and reusability is advantageous for mitigating CO2 emissions discharged from the iron manufacturing industry, and will surely contribute to the sustainable development of the iron manufacturing industry.
- This article is part of the themed collection: Green Chemistry 2020 Emerging Investigators