A new strategy for CO2 storage and Al2O3 recovery from blast furnace slag and coal fly ash by employing vacuum reduction and alkali dissolution methods

With the growing awareness of carbon emission reduction and environmental protection, the CO2 storage using industrial solid waste as the storing carrier has recently gained an extensive attention. A new strategy for CO2 storage and Al2O3 extraction from blast furnace slag (BFS) and coal fly ash (CFA) has here been proposed by using vacuum reduction and alkali dissolution methods. The results show that the mullite (Al6Si2O13), gehlenite (Ca2Al2SiO7), and akermanite (Ca2MgSi2O7) in CFA and BFS were converted to Fe–Si alloys and CaO·xAl2O3 during vacuum reduction. Thereafter, the CaO·xAl2O3 was dissolved in a mixed solution of Na2CO3 and NaOH to generate CaCO3 and NaAl(OH)4. Finally, the Fe–Si alloy and CaCO3 mixture in the alkali leaching residue were separated using magnetic separation to realize the CO2 storage and metal recovery. In this process, the CO2 storage capacity attained 241 kg t−1 BFS and the Al2O3 recovery efficiency was 80.61 %, indicating that an efficient storage of CO2 and Al2O3 extraction were achieved simultaneously. In addition, there was almost no generation of waste slag or waste liquid in this process, which indicated that an environmentally friendly and efficient process for CO2 storage, as well as valuable metal recovery from industrial solid wastes was obtained.