Carbonation of steel slag for mineral CO2 sequestration: a novel method for desorption of CO2-loaded monoethanolamine (MEA).

This study presents a novel method for integrating amine-based CO₂ capture with mineral carbonation by using steelmaking slag to regenerate monoethanolamine (MEA) solutions. Unlike conventional thermal desorption methods, this approach enables chemical CO₂ desorption under mild conditions while simultaneously sequestering CO₂ as stable carbonates. Although mineral carbonation and MEA-based capture have been widely studied separately, their combination via reactive calcium-rich industrial waste remains largely unexplored. In this work, steel slag was contacted with CO₂-loaded MEA solutions to assess its dual role in promoting CO₂ release and mineralization. The effects of key process parameters-including slag-to-water ratio, CO₂ flow rate, temperature (25-75 °C), MEA concentration (0-0.5 M), and water type (service vs. seawater)-were systematically evaluated. Carbonation efficiency was quantified via TGA, XRF, and XRD analyses. Results showed that MEA significantly enhanced CO₂ uptake and accelerated carbonate formation, especially at higher temperatures and in seawater. Kinetic modeling revealed that the reaction follows a mixed-controlled mechanism involving both surface reaction and product-layer diffusion, with an apparent activation energy of 5.6 kJ/mol. The study demonstrates the feasibility of combining CO₂ desorption and mineralization in a single step, offering a low-energy alternative to MEA regeneration and a sustainable use for steel slag in CO₂ capture systems.