Exploringthe Enhancement on CO₂ Mineralizationof Solid Wastes via Amine-Looping

CO₂ mineralization-coupled amine-looping has great potential for large-scale CO₂ emissions reduction. However, it remains uncertain if amine-looping successfully improves CO₂ sequestration of typical industrial solid wastes of steel slag and iron tailings and whether this enhancing occurs through an increase in CO₂ concentration in solution or by promoting the leaching of calcium ions. Herein, we systematically evaluate the CO₂ mineralization of steel slag and iron tailings in the presence of three typical amines: monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ). Results show that all three amines could significantly enhance the CO₂ mineralization performance of steel slag and iron tailings, especially in PZ solution, where the CO₂ sequestration capacity of steel slag and iron tailings is promoted from 114.4 and 12.6 g/kg to 202.4 and 50.6 g/kg, respectively. Furthermore, Ca²⁺/Mg²⁺ leaching experiments indicate that the enhanced CO₂ mineralization by amine may be a result of more CO₃^2– provided by amine-generated carbamate, which facilitates the formation of precipitates by combining with Ca²⁺/Mg²⁺. Additionally, the carbonation efficiency of steel slag is stabilized at approximately 51 and 71% by recycling MEA and PZ in four successive reactions, showing a good potential in sequestrating CO₂ with an affordable additive cost.