Optimization of Ammonium Sulfate Crystallization Under the Action of Ammonium Sulfite Based on Response Surface Methodology

ABSTRACT To investigate the effect of doped ammonium sulfite on the solubility, supersolubility, and crystallization of ammonium sulfate mother liquor, this paper measured solubility and supersolubility using the laser method. A regression model was constructed via response surface methodology (RSM) to research the mechanism and interaction of three factors—stirring rate, pH value, and oxidation rate—on ammonium sulfate crystallization. The study showed that the solubility of ammonium sulfate decreased as ammonium sulfite increased, attributed to the common‐ion effect, salting‐out, and weaker interactions between ammonium sulfate and water. Conversely, the mesostable zone width broadened with increased ammonium sulfite content, as sulfite reduced the solution's acidity. The influence of the factors on both crystallization amount and average particle size was: oxidation rate > stirring rate > pH value. The optimal combination was obtained at a stirring rate of 303 r·min −1 , pH value of 6, and oxidation rate of 100%. Under these conditions, the theoretical crystallization amount was 30.268 g/100 mL H 2 O, with an average particle size of 1.475 mm.