The Effect of Nonelectrolyte Additives with Hydrophilic and Hydrophobic Hydration on the Growth of KDP Crystals from Aqueous Solutions

Abstract

The effect of nonelectrolyte additives with hydrophilic and hydrophobic hydration on the growth of potassium dihydrogen phosphate (KH₂PO) crystals in the kinetic mode at solution saturation temperatures of 323 and 303 K and a relative supersaturation of 0.025 has been experimentally investigated. The additives are found to affect differently, depending on their shape, concentration, and face index. It is revealed that the growth rate of {101} faces increases in the presence of additives with hydrophilic hydration of molecules and decreases in the case of hydrophobic additives. A model is proposed to explain the difference in the influence of the additives studied on the crystal growth. The influence is determined by the changes in the water structure in the surface layer of the crystallization solution; this conclusion must be taken into account when growing crystals from aqueous solutions in the presence of nonelectrolyte additives.