Kinetics of Active Seed-Induced Al(OH)₃ Precipitation from NaAlO₂ Solution for Recycling Aluminum from Spent Lithium-Ion Batteries

In the recycling process of spent lithium-ion batteries, the presence of a certain amount of aluminum ions not only increases the alkali consumption for iron and aluminum removal but also affects the purity of nickel, cobalt, manganese salts, and iron phosphate, thereby hindering the preparation of battery-grade products. Herein, the precipitation process of aluminum hydroxide from supersaturated sodium aluminate solution was investigated across varying temperatures with the addition of minimal quantity of active seeds. X-ray diffraction analysis identified gibbsite and bayerite crystallization in the active seed phases. Assessment of product particle size distribution using power spectral density indicated median particle sizes of 9.70, 18.89, 35.32, and 51.78 μm at temperatures of 45, 55, 65, and 75 °C, respectively, suggesting that elevated temperatures favored product particle size growth. Additionally, to elucidate the precipitation mechanism, the kinetic equation was augmented with the inclusion of instantaneous seed coefficient and specific surface area, yielding an apparent activation energy of 83.52 kJ/mol.