Abstract
Kinetics of spontaneous crystallization of potassium nitrate from its supersaturated aqueous solutions has been studied simultaneously by electrical conductance and optical transmittance methods. It was found that spontaneous crystallization of potassium nitrate was accompanied by aggregation of crystals. Growth of salt crystals was in the kinetic mode of the growth process, and was described by the equation of the first order regarding supersaturation of solution. The mechanism of aggregation and intergrowth of crystals during bulk crystallization via formation of nucleus-bridges between crystals found earlier for several salts was confirmed. Specific surface energy of potassium nitrate was evaluated on the basis of the above mechanism of aggregation and intergrowth of crystals. The established value of the specific surface energy was reasonable and agreed satisfactorily with the available literature data. Examination of crystal deposit after completion of crystallization allowed detecting crystal agglomerates of freakish and irregular forms, which may be considered as the direct confirmation of the above mechanism of intergrowth of crystals. Kinetics of crystallization, aggregation and size distribution of salt crystals after completion of crystallization have been satisfactory described by the earlier proposed model of the crystallization process. An excellent agreement was established between the experimental data on potassium nitrate solubility in aqueous solutions found in the present work and those available in the literature.
Highlights
Very scarce information about crystallization kinetics of potassium nitrate in aqueous solutions is available in the literature
For its evaluation we considered the parameters of the unit cell for a modification of KNO3 with orthorhombic structure
The experiments performed showed that spontaneous crystallization of potassium nitrate from its supersaturated aqueous solutions is accompanied by aggregation of salt crystals
Summary
Very scarce information about crystallization kinetics of potassium nitrate in aqueous solutions is available in the literature. There are only a few works where crystallization of potassium nitrate from aqueous solutions was studied [1,2,3]. The order of the crystal growth process was found to be 1 and the activation energy of the growth process was 31 kJ·mol−1 [1]. Graber et al [2] studied the growth of seed crystals of sodium and potassium nitrates from aqueous solutions in a perfectly stirred batch crystallizer. The growth rate of different faces of single potassium nitrate crystals from aqueous solution was studied by Lacmann et al with the aid of optical microscopical method [3]. Examination of the surface morphology showed that crystal faces had a flat structure; no significant objects were found
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