A critical review of CO2 storage by steel slag: Part I direct carbonation reaction kinetics models.

With the rapid advancement of industrialization, the rising demand for resources and associated greenhouse gas emissions have intensified global environmental concerns. Carbon Capture, Utilization, and Storage (CCUS) technologies utilizing industrial solid wastes have emerged as promising solutions to advance carbon neutrality and circular economy goals. Among these industrial solid wastes, steel slag (SS), has attracted increasing attention in CO2 storage technologies due to its high reactivity with CO2 and considerable sequestration potential. This review systematically evaluates the CO2 storage pathway by SS and elucidates the direct carbonation reaction mechanisms of SS under gas-solid, liquid-solid, and gas-liquid-solid conditions. Key challenges are discussed, including surface passivation, gas-liquid mass transfer limitations, and the optimization of process conditions. Three dominant kinetic models-shrinking core, surface coverage, and random pore models, are analyzed to interpret multistep reaction behaviors and guide process optimization. Additionally, the review highlights the role of experimental data in deriving kinetic parameters and guides their integration into reactor-scale modeling. By synthesizing existing knowledge and outlining future research priorities, this work aims to enhance the direct carbonation performance of SS and promote its industrial deployment as a sustainable carbon capture solution aligned with environmental and policy objectives.