A Sustainable Process for Efficient Extraction of Lithium, Aluminum, and Phosphorus from Montebrasite

In this paper, the CaSO4 and CaO mixed roasting process was used to selectively recover Li, P and Al from montebrasite ore, in order to solve the difficult separation of P and Al in sulfuric acid roasting process. First, the theoretical feasibility of the roasting process was verified by thermodynamic analysis of the reaction materials. Second, systematic experiments were conducted on the main conditions of the roasting process to determine the optimal roasting parameters, which are roasting temperature of 820 °C, roasting time of 60 min, and theoretical amounts of CaSO4 and CaO. The water leaching method was adopted to extract Li from the roasting slag with a extraction rate of 99.3%, while the extraction rates of P and Al were both less than 0.02%, achieving efficient separation of Li. After impurity removal, Li2CO3 with a purity of 99.6% was prepared by carbonate precipitation and characterized by XRD and SEM. Third, 99.2% of P was extracted from the water leaching residue by leaching with the mixture of sulfuric acid and phosphoric acid, and crude phosphoric acid was prepared. In this process, the extraction rate of Al was only 0.41%. Fourth, 99.3% of the Al was extracted by a sulfuric acid activation and water leaching processes, and anhydrous aluminum sulfate was prepared by evaporation and crystallization. Finally, the tailings obtained were CaSO4. The technology proposed in this paper achieved the selective recovery and efficient separation of Li, P, and Al from montebrasite ore and also realized the recycling of CaSO4. It is an efficient, clean, and sustainable treatment process for montebrasite ore.