Preparation of Ultradispersed KNO3 Powders in Mixed Reverse Micelles of Tergitol NP-4 + AOT by Isothermal Evaporation Crystallization

Abstract

The size, composition, and morphology of KNO3 particles produced under the conditions of isothermal evaporation crystallization were found to depend on the concentration ratios of surfactant in mixed reverse micelles of Tergitol NP-4 + AOT, content of water pseudophase (wo = 1.1–4.4), concentration of salt (0.8–2.5 M), and temperature (20–40 °C). In optimal conditions (wo = 2.2, T = 35 °C), powders with micrometer particles of tubular structure are formed in reverse micellar solutions of Tergitol NP-4 in n-decane. The addition of 0.01–0.05 M AOT results in the splitting of tubes, a 103-fold increase in the specific surface area, and formation of whisker-type particles 5–10 μm long and 0.2–0.5 μm thick. We used photon-correlation spectroscopy and a spinning drop procedure, which showed that the addition of AOT to Tergitol NP-4 leads to a decrease in the hydrodynamic diameter of reverse micelles, and interfacial tension passes through the maximum, which increases with growing temperature.