Carbide Slag as a Calcium Source for Bauxite Residue Utilization via Calcification–Carbonization Processing

The calcification–carbonization method can effectively treat bauxite residue. In this paper, carbide slag is used as the calcium source of the calcification process to treat bauxite residue, which greatly reduces the process cost while realizing the utilization of two kinds of solid waste resources. Through the investigation of the influencing factors of the calcification process, we ascertained the optimal calcification condition is the calcium-to-silicon ratio of 2.5, calcification temperature of 160°C, the liquid-to-solid ratio of 5 : 1, and reaction duration of 60 min. Under this condition, a Na₂O recovery rate of 94.7% was achieved, and the extraction rates of Al₂O₃ reach 33.9%. The main phase composition of tailings after treatment is CaCO₃ and CaSiO₄, which are environmentally harmless and can be reused as raw materials. On the other hand, using carbide slag to treat 1t bauxite residue can save 15.69$ of production cost, and the comprehensive economic benefit can reach 26.67$ per ton. Therefore, carbide slag is promising as a calcium source in the treatment of bauxite residue.