Reduction of Potassium in Alumina Product During Seeded Precipitation

In the alumina production process, potassium from bauxite transfers to the alumina product through digestion and precipitation, posing significant risks to the subsequent aluminum electrolysis. The current understanding of this transfer behavior, especially the distribution patterns of potassium, remains inadequate. This research examines the influence of key parameters—including K2O concentration, seed addition amount, final precipitation temperature, and the molar ratio of the sodium aluminate solution—on the precipitation of potassium. The findings demonstrate that increasing the seed addition, the initial K2O concentration in the solution, the final temperature, and the solution molar ratio all promote the precipitation efficiency of potassium. Moreover, it was observed that raising the seed addition, solution molar ratio, and final temperature effectively increases the proportion of coarse particles in the precipitated product. Conversely, a higher K2O concentration leads to a greater fraction of fine particles. Under typical industrial conditions (COH− = 4.8 mol/L, K2O = 70 g/L, αk = 1.53, initial temperature of 75 °C, final temperature of 37 °C, seed addition of 700 g/L, and a precipitation duration of 40 h), only about 0.19% of the potassium from the initial solution transferred into the aluminum hydroxide product.