Exploring the Enhancement on CO₂ Mineralization of 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 CO32– 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.