I'm going to use lime milk to precipitatie magnesium from brine. Which is the best of lime / water ratio to produce lime milk. What are the most influential parameters for its preparation?
A reasonable concentration for the milk-of-lime suspension might be 30 wt% of Ca(OH)2; above this ratio tends to become too thick to be readily pumpable.
Dear C. A. Queiroz
Hi,
Its true, This is a critical value for milk of lime. But a suspension with 30 wt% of Ca(OH)2, can precipitates magnesium ions to form of Mg(OH)2? I got a lime milk suspension with 54 gr CaO (97% purity) and 0.5 L H2O ( lime milk pH= 11.97) and added to brine with a concentration of 182 g/L magnesium chloride, but the final pH (after adding lime milk to the brine) was 8.67. So didn't precipitate any Mg(OH)2. In addition, the amount of lime was calculated based on the stoichiometry, but the result wasn't satisfactory.
In your opinion, what is the solution?
Given the low solubility of Ca(OH)2 in water and at the aqueous solution, and the fact that the following equilibrium should be displaced to the right ― MgCl2 (aq) + Ca(OH)2 (aq) ↔ Mg(OH)2 (s)↓+ CaCl2 (aq) ― it is necessary excess of Ca(OH)2. The solid suspended lime dissolves progressively, faster upon agitation, while Mg(OH)2 precipitates from the solution. The excess of suspended Ca(OH)2, necessary to saturate the aqueous solution phase, settles with Mg(OH)2. The solubility product (Ksp) of both hydroxides determines their concentration in the aqueous solution phase.
What concentration of Ca(OH)2 did you use finally n how was the result? Do you also use Na2CO3 for Ca precipitation? thanks
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