Calcification-Carbonation Method for Bayer Red Mud Treatment: Carbonation Performance of Hydrogarnets.

Hydrogarnets are vital intermediate products in the calcification- carbonation method, which is designed for Bayer red mud treatment. Their carbonation performance greatly depends on SiO substitution. In this study, different SiO-substituted hydrogarnets were synthesized and characterized. Then, batch experiments were performed to evaluate the potential effects of important parameters such as CO pressure, and SiO substitution degree (x) on the carbonation process. The SiO substitution degrees of the hydrogarnets synthesized at 60, 120, 180, and 240°C were 0.27, 0.36, 0.70, and 0.73, respectively. As the SiO substitution degree increased, the hydrogarnet carbonation extents gradually declined. With an increase in CO pressure, the hydrogarnet carbonation percentages increased gradually and rose from 80.33% to 98.19% within 120 min. The phases detected in the carbonized products were strip-like aragonite as well as some calcite; the Al-rich and Si-rich phases in the carbonized products were amorphous.