Question

Why does double magnesium bicarbonate requires double amount of Lime for softening ​??

Answer 1

Answer:

When high magnesium water is softened, excess lime needs to be added to raise the pH above 11, and magnesium hydroxide precipitates out. After treatment, enough carbon dioxide must be added to neutralize the excess hydroxide ions, as well as convert carbonate ions to bicarbonate ions.

Answer 2

LIME SOFTENING

One of the most frequent procedures for softening water is chemical precipitation. Lime (calcium hydroxide, Ca(OH)2) and soda ash are commonly used chemicals (sodium carbonate, Na2CO3).

REASONS FOR USING DOUBLE AMOUNT OF LIME FOR SOFTENING:

* Lime is used to eliminate carbonate hardness-causing compounds. Chemicals that induce non-carbonate hardness are removed using soda ash.

* Hardness-causing minerals generate almost insoluble precipitates when lime and soda ash are added. Magnesium hardness is precipitated as magnesium hydroxide (Mg(OH)2). The precipitates are subsequently removed using traditional coagulation/flocculation, sedimentation, and filtering techniques.

* This hardness level is preferred to avoid corrosion issues caused by water that is excessively soft and has little or no hardness. CO2 does not add to hardness, but it interacts with the lime and consumes part of it before the lime is consumed.

Two molecules of lime are utilized for every molecule of magnesium bicarbonate hardness eliminated.