Impact of Lactose Phosphate Impurities on Lactose Crystallization: Deionization as Effective Pretreatment

Commercial α-lactose monohydrate powders contain trace amounts of lactose phosphate impurities. In this work, the influence of lactose phosphate on the crystallization of α-lactose monohydrate from aqueous solutions is experimentally investigated by varying both the seed mass and the initial supersaturation. A novel approach based on pH measurements is proposed to quantify the concentration of lactose phosphate in solution and its incorporation into lactose crystals during the crystallization process. Deionization of lactose solution prior to crystallization using ion-exchange beads effectively removes the lactose phosphate and enables a clear assessment of the impact of these ionic impurities on the crystallization kinetics and the aspect ratio of the resulting lactose crystals.