Enhanced dissolution rate of magnesium hydroxide via magnesia/ammonium acetate hydration system: statistical optimization and possible mechanism

Abstract

BACKGROUND The dissolubility of magnesium hydroxide is often the main factor limiting its application effect in the environmental field, and the dissolution rate of magnesium hydroxide during its synthesis is also worthy of attention. In this paper, response surface methodology was used to synthesize magnesium hydroxide with different dissolution rates through a magnesium oxide/ammonium acetate hydration system, and the possible formation mechanism as well as dissolution performance is discussed. RESULTS Compared with the hydration temperature and time, the concentration of ammonium acetate has a more significant effect on the dissolution rate of hydrated magnesium hydroxide. A maximum dissolution rate of 43.8 ± 0.3 mmol min−1 mol−1 magnesium hydroxide could be obtained when the working factors were ammonium acetate concentration 15 g L–1, hydration temperature 75.5 °C and time 112 min. CONCLUSION The correlation study between structural characterization and the dissolution test shows that the complexation and replacement of acetate, in situ generation and release of ammonia appear to have some critical effects on magnesium hydroxide crystallization behaviour and induce the formation of thin, curved and defective structures. Crystals with such structures have been reported to have a higher dissolution activity. The results of this study provide an indication for screening hydration synthetic agents of high‐dissolution‐rate magnesium hydroxide. © 2020 Society of Chemical Industry (SCI)