Activation and utilization of tailings as CO2 mineralization feedstock and supplementary cementitious materials: a critical review

Abstract

Activation and utilization of mine tailings as feedstock for CO2 mineralization and supplementary cementitious materials (SCMs) have attracted great interest in the mining and concrete industries. In this work, a state-of-the-art review on the two utilization strategies and associated activation and pre-treatment methods was provided, aiming at promoting the reuse and reprocessing of mine tailings at a commercial scale. Based on the chemical, mineralogical, and physical characteristics, principles for screening available mine tailings as CO2 mineralization feedstock and SCMs were reviewed and discussed first. Then, basic activation methods were highlighted to improve the reactivity of mine tailings as CO2 mineralization feedstock and SCMs, including thermal, mechanical, and chemical activation. The mechanisms behind each activation method were elaborated, and the energy consumption and optimization of activation treatment were also evaluated. Besides, carbonation conditions affecting the carbonation efficiency of mine tailings were reviewed systematically. In addition, the influence of the utilization of the activated mine tailings as CO2 mineralization feedstock and SCMs on the extraction of trace elements was also examined, and key knowledge gaps were identified and discussed. The critical review concluded that after integrated thermal and mechanical activation, silica-rich mine tailings with kaolinite and a high content of Al2O3 + Fe2O3 + SiO2 (over 80%, by mass) could have a high potential as SCMs. Activated (ultramafic) mine tailings with high Mg/Si and Mg/Fe ratios (of more than 1.5) were susceptible to CO2 mineralization. Overall, the optimal thermal and mechanical activation conditions for pre-treatment of mine tailings as CO2 mineralization feedstock and SCMs were found to be approximately the same, which might facilitate the up-scaled utilization and activation.