Precipitation rate and particle size distribution of seeded precipitation proceeding in sodium and potassium aluminate solutions

The precipitation rate and particle size distribution(PSD)for pure sodium aluminate solution and potassium aluminate solutions were investigated. The XRD, SEM and TG/DTG curves were used to study the products of sodium aluminate solution and potassium aluminate solution. The results show that the precipitation rate of potassium aluminate solution is larger than that of sodium aluminate solution, and the rate increases with the decrease of (original) α_k of caustic aluminate solution under the same conditions. There are dramatic discrepancies of PSD during the same seeded precipitation condition between sodium aluminate solution and potassium aluminate solution. The XRD patterns of products show that the crystals of potassium aluminate solution have better crystallinity than that of sodium aluminate solution, but the TG/DTG curves of products of sodium aluminate solution and potassium aluminate solution have no obvious difference. These discrepancies are similar in solutions of different α_k(1.45, 1.55, 1.65). It is considered that the difference of nucleation rate between sodium aluminate solution and potassium aluminate solution is the reason for the discrepancy of precipitation rate and PSD during seeded precipitation.