Investigation of Selected Alcohols as Antisolvents in the Crystallization Behavior of Ammonium Dihydrogen Phosphate from Aqueous Solutions

Abstract

AbstractMeasurements of temperatures Tw of water at initial temperature 30 °C and temperature Ts of aqueous ADP solutions saturated at 30 °C against the content x of three alcohols (i.e. methanol, ethanol and n‐butanol) added as antisolvents at different rates reveal regions of constant temperature in the maxima of the Tw(x) plots in water and in the vicinity of occurrence of three‐dimensional (3D) nucleation of the Ts(x) plots in the solutions. These regions of constant temperature, represented by the antisolvent content x, lie between x1 and x2 such that Δx = (x2−x1) > 0. It is found that the antisolvent content range Δx decreases with an increase in the maximum constant temperatures in the Tw(x) and Ts(x) plots. From an analysis of the data of x1 and x2 for different maximum temperatures obtained from the Tw(x) and Ts(x) plots it is argued that the maximum value of Δx is related to the withdrawal of the heat of reactions by the cooling system. However, in the case of ADP solutions, the value of Δx representing the width of the maxima due to 3D nucleation in the Ts(x) plots is also related to the reorganization of crystalline clusters to form stable 3D nuclei during antisolvent crystallization.