Advances in concurrent CO2 sequestration and heavy metal mobilization during fly ash carbonation: A review

The escalating atmospheric CO₂ concentration and concomitant ecological crises underscore the urgent need for innovative carbon capture and utilization strategies. Fly ash (FA), a global industrial byproduct with annual production exceeding 1 billion tons, presents a promising opportunity for simultaneous CO₂ mineralization and heavy metal stabilization. This review systematically examines recent advancements in FA-mediated CO₂ sequestration coupled with heavy metal immobilization, addressing critical knowledge gaps in their synergistic mechanisms. We analyze the interplay between carbonation pathways and heavy metal fate, the effects of key reaction parameters on Ca²⁺ leaching efficiency and metal stabilization, and the impact of pre-treatment methods such as mechanical activation and acid/alkali modification. Furthermore, we review the application of theoretical calculations for atomic-scale mechanism analysis and process optimization via machine learning. Finally, we identify existing challenges—including kinetic limitations, pH-dependent metal mobilization, and economic viability—and propose future research directions for enhancing process efficiency and environmental safety. This review aims to facilitate the development of fly ash-based technologies for dual carbon sequestration and pollution control, contributing to sustainable industrial solid waste management.