CO2 Mineral Sequestration and Faujasite Zeolite Synthesis by Using Blast Furnace Slag: Process Optimization and CO2 Net-Emission Reduction Evaluation

CO2 mineral sequestration is one of the most promising strategies for combating global warming. However, its industrial applications of CO2 mineral carbonation are limited due to the concerns of energy and cost consumption. Simultaneously, recovery of valuable byproducts is essential for favorable economic viability during the mineralization process. In this study, a novel process combining CO2 mineral sequestration and zeolite synthesis by using blast furnace slag was proposed. Si/Al-gel was first prepared by leaching and precipitation of the slag, followed by hydrothermal reaction to synthesize faujasite type zeolite. The process optimization and CO2 net-emission reduction evaluation of the proposed route were conducted in this study. A sole phase faujasite zeolite with high specific surface area (721 m(2)/g) was successfully synthesized under the optimal hydrothermal conditions. The Si/ Al-depleted precipitated mother liquid (rich in MgSO4) together with the CaSO4 center dot 0.5H(2)O leaching residue was used to mineral sequestrate CO2. The total amount of CO2 sequestrated by processing one ton slag was 398 kg. Preliminary evaluation of CO2 netemission reduction indicated that 52 kg of CO2 can be permanently stored for 1000 kg of slag processing after deducting the CO2 released in this process. The major component of blast furnace slag was fully utilized in this process, realizing the double benefits of CO2 emission reduction and solid waste disposal as well as exhibiting great potential for industrial application.