Innovation at its best

[Kartik Kamat]

phosphoric acid when produced from the reaction with calcium phosphate exists as a mixture with calcium chloride. initially the americans were  inventing a process to separate calcium chloride from aqueous medium containing phosphoric acid . The researchers gave up on this method of separation because calcium chloride was highly soluble in water and they failed to separate phosphoric acid from it . This was when world's one of the best technology for phosphoric acid extraction kicked in. The innovative process was developed by IMI ( i guess it  stands for Israel Mining Industry  ). They used amyl alcohol as a solvent for liquid liquid extraction which preferentially dissolves phosphoric acid. and more so the distribution coefficient of this process is highly dependent on the calcium ion concentration . This means any change in the concentration of calcium ions disturbed the efficiency of extraction. then the organic part is treated with water (called soft water ) for back extraction of Phosphoric acid. As a result we get Dilute phosphoric Acid . So the Calcium chloride that was cursed by the americans actually proved to be a boon. interestingly when this type of process was adopted in India there were just 2 plants (both in Israel ) using this technology. Today this Process is effectively used in most of the phosphoric acid plants to separate it from calcium chloride as well as other aqueous impurities.   

[Vishwanath Dalvi]

You need to explain the background more.  Why was calcium chloride formed?  Why as sulfuric acid not used?

[Kartik Kamat]

Sir this process was used by Solaris Chemtech Limited ( formerly BILT) . The manufacturing unit used to produce Sodium Hydroxide. So they used the Chlorine to form Hydrochloric acid which then they used for reacting with rock phosphate. Thus calcium chloride was formed.