Stabilization of red mud using mineral carbonation

Abstract

Mineral carbonation is a promising technique to reduce the atmospheric carbon dioxide (CO₂) concentration via precipitation of stable carbonates. This study examined the mineralization potential of red mud, a byproduct of the aluminium manufacturing industry. The alkaline nature of red mud has hindered its widespread utilization, causing issues associated with its storage and disposal. The limited calcium concentration and high iron content pose challenges with regard to CO₂ mineralization, and the optimal conditions for mineralization have not been explored well. In the present study, three different temperatures (25 °C, 45 °C, and 65 °C) at high pressure of 10 bar were employed to study the mineralization potential of red mud. The red mud mineralized at 45 °C outperformed others. After mineralization, compressive strength increased by 11.6 %, 64 %, and 50 % at 25 °C, 45 °C, and 65 °C, respectively. A marginal increase in calcite precipitation and noticeable reduction (720–510 nm) in critical pore size was observed due to mineralization at 45 °C. Microstructural study revealed that the hematite phase in the red mud provided nucleation site for the carbonate phase, contributing to a denser microstructure. The agglomeration of mineralized phases indicated a marginal increase in true density, leading to a denser microstructure and higher strength after mineralization. Furthermore, dimensional stability (in water immersion) and acid neutralization capacity of mineralized red mud were examined.