Reactive crystallization of magnesium hydroxide

The present work deals with the reactive crystallization of magnesium hydroxide, a well-known sparing soluble material, from magnesium chloride with calcium hydroxide. Magnesium hydroxide is produced industrially by the precipitation from brine with... 

Several studies have been done on the reactive crystallization of magnesium hydroxide. Murotani et al.(l) precipitated magnesium hydroxide by adding ammonia to mixed solution of magnesium chloride and ammonium chloride. In this reaction system hexagonal crystals of magnesium hydroxide were obtained... 

Crystallization of magnesium hydroxide by a continuous mixed suspension mixed product removal crystallizer was conducted to make clear the characteristics of reactive crystallization kinetics of magnesium hydroxide, which was produced by the precipitation from magnesium chloride with calcium hydroxide. The following operating factors were investigated affecting the crystallization kinetics the initial concentration of feeds, residence time of reactants, feed ratio of reactants, and concentrations of hydroxide and chloride ions. 

Dabir et al showed that the kinetic order i is written by Equation 11 for the reactive crystallization of Mg(OH)2 produced by magnesium chloride and sodium hydroxide. 

Reactive crystallization experiments of magnesium hydroxide were conducted to clarify the characteristics of reactive crystallization kinetics by a continuous MSMPR crystallizer. 

It is essential to clarify the crystallization kinetics of magnesium hydroxide and to investigate the influence of various factors on the reactive crystallization characteristics of magnesium hydroxide for better understanding of its crystallization process. The aims of this study are to discuss the followings ... 

Table IV shows the solubilities of various alkali feeds. In general, smaller solubility means that the movement of OH is controlled by ion pair of solute. So it may be difficult for Mg to collide with OH in calcium hydroxide which has the smallest solubility. From SEM photographs of magnesium hydroxide in Figure 3, primary particles are formed in the system of calcium hydroxide, whereas larger primary particles are formed and agglomerated easily in other alkali feed systems which have larger solubility. Then dominant particle size of agglomerated particle becomes larger. Therefore, the solubility may be the key property among the above-mentioned properties. This tendency was also observed in the reactive crystallizations of other carbonates, that is, calcium carbonate(9) and lithium carbonate(lO).

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