Precipitation of magnesium hydroxide

Abstract

Mg(OH)2 was precipitated from MgCl2 and NaOH solutions in a continuous agitated reactor and the effects of the solutions concentration, residence time of suspension in the reactor and stoichiometric ratio of the reacting components on the properties of Mg(OH)2 were studied. The properties of the resulting suspension were evaluated on the basis of its filtration resistance α as determined by a filtration test. The value of α is inversely proportional to mean residence time of the suspension in the reactor and it depends, at the same time, on the ratio of concentration of the precipitated solutions γ = [MgCl2]/[NaOH]. A critical value of γ can be assessed for a continuous reactor and when this value is exceeded a comparatively well filtering suspension with α ≦ 1012 m · kg−1 is always obtained. The relationship between α and the parameters of the precipitation process was expressed quantitatively within the framework of the exiting theories.

Batch precipitation of alkaline earth carbonates. Effect of reaction conditions on the filterability of resulting suspensions

“…To establish a correlation between the performances of a precipitation and separation equipment, it is necessary to know first the dependence of the filtration characteristics of the formed slurry on the conditions of precipitation. For the case of continuous precipitation this problem was already solved earlier (Sóhnel and Marecek, 1978). The present study aims at establishing the mentioned dependence for batch precipitation carried out by adding rapidly a solution of one component to an agitated solution of the other component.…”

Comment on “Recovery of Magnesium from Industrial Effluent and Its Implication on Carbon Capture and Storage”

“…However, when these reactants are obtained by thermal decomposition of dolomite or calcite, CO 2 is released. An alternative reactant is NaOH, but again, CO 2 binding cannot be achieved.…”

The kinetics of gypsum precipitation, the inhibiting effect of citric acid and its use in the differential precipitation of Mg(OH)2 from CaSO4·2H2O

“…Unlike in the case of gypsum, the precipitation kinetics of magnesium hydroxide is naturally highly dependent on the pH of the reaction, since one of the constituents is the hydroxide ion [128]. Of course, the supersaturation is the most important factor making the crystallization of Mg(OH)2 basically instantaneous at high supersaturation [127][128][129][130][131]. Also, while it was shown that the precipitation of gypsum can be slowed by various means, the attempts to do the same with magnesium hydroxide were less successful, sometimes completely futile [127,130,132,133].…”