Optimizing Seed-Induced Nucleation for Enhanced Al(OH)3 Crystal Precipitation from Supersaturated Potassium Aluminate Solution

Potassium alunite is a potential mineral resource of potassium and aluminum that can serve as a valuable resource. An effective potassium and aluminum recovery method is developed using gradient leaching with a KOH sub-molten salt. The key part of this process is seeded precipitation of the potassium aluminate leach solution. Therefore, this study aims to optimize the seeded precipitation process by investigating the effects of alkali concentration, molecular ratio, stirring rate, temperature, and seed coefficient on the precipitation ratio and particle size of Al(OH)₃. The results show that alkali concentration, molecular ratio, temperature, and seed coefficient are key factors influencing seeded precipitation. Furthermore, the process is optimized by using these four identified factors as variables. A 9L(34) orthogonal experiment determines optimal conditions for maximizing the precipitation ratio and achieves the desired average particle size. Under the optimal condition of 200 g L⁻¹ alkali concentration, 1.5 molecular ratio, 1.0 seed coefficient, and 343.15 K temperature, the precipitation ratio reaches 54% and the average Al(OH)₃ particle size is 114 µm. Further work is required to scale up this optimized seeded precipitation process and evaluate applications of the Al(OH)₃ product.