Abstract
Mineral carbonation has garnered interest as a way of permanently fixing carbon dioxide. Due to the benefits of permanent storage and abundant mineral resources, mineral carbonation is one of the most effective strategies for sequestering CO2. The combination of mineral processing for primary metal recovery and mineral carbonation of tailings for carbon sequestration is an emerging field of study with the potential to minimize the carbon sequestration costs as the material is already ground.
The present work looked at low-pressure, gas–solid carbonation of ultramafic tailings in a moist environment. Carbonation efficiency was modeled using a systematic design of experiments and response surface approach. The variables studied include particle size, temperature, water to solid ratio, buffer, catalyst, and reaction time.
The carbonation extent of the tailings primarily containing serpentine, was studied a function of temperature at high temperature in first stage (550 oC - 750 oC) and low temperature in the last stage (0 oC - 50 oC), particle size (0 - 75 μm) and biocatalyst (Carbonic Anhydrase). The incongruent CO2 van der Waals molecular diameters with the octahedral-tetrahedral lattice constants of serpentine were used to explain the mild carbonation reactivity. It was determined that serpentine requires a thermal pre-treatment step to remove hydroxyl groups and a way to improve yield, resulting in the chemical transformation to meta-serpentine, which is a mineral composed of isolated SiO4 tetrahedra linked by octahedrally coordinated magnesium ions. This step is of great importance as it controls Mg2+ leaching, one of the carbonation reaction limiting factors. Previous studies have focused on the optimization of thermal activation by determining the ideal activation temperature. However, so far, none of these research have taken into account the effects of thermal activation on the effectiveness of aqueous-phase mineral carbonation at normal to moderate temperature and low pressure under flue gas circumstances with influence of Enzyme. The optimal mineral composition for carbonation is determined to be a blend of several amorphous phases that have been discovered. This study emphasizes the significance of the mineral composition acquired during the removal of hydroxyl groups and its influence on the accessibility of magnesium during the process of dissolving in the carbonation reaction. Additionally, it examines the role of biocatalysts (CA) in facilitating the hydration of CO2 and its subsequent precipitation as magnesium carbonate.