Partial purification of wet-process phosphoric acid with acetone and ammonia

An improved process for the partial purification of crude wet-process phosphoric acid containing about 25 percent to about 55 percent by weight P.sub.2 O.sub.5 which comprises:

• 1. mixing said crude acid with acetone and ammonia, while maintaining same at a temperature in the range from about 25.degree. C. to about the boiling point of the solution for a period of time ranging from 2 minutes to 10 minutes, wherein for each mole of P.sub.2 O.sub.5 in the crude acid, the amount of ammonia is in the range of 0.2 to 0.6 moles, and the amount of acetone is in the range from 1 to 5 pounds for each pound of crude acid;
• 2. subsequently allowing, during a period ranging from about 1 to about 10 minutes, the resulting mixture of step 1 supra to settle into two separate liquid layers, one being vertically disposed over the other, wherein the upper layer contains purified acid in acetone and wherein the bottom layer having a viscosity at 25.degree. C. in the range of 40 to 5000 centipoises contains a substantial portion of the impurities originally contained in the crude wet-process phosphoric acid;
• 3. separating the two liquid layers formed in step 2, supra;
• 4. distilling all the acetone and part of the water from the upper layer solution to obtain partially purified acid as a product;
• and
• 5. distilling all the acetone and part of the water from the bottom liquid layer to recover the impure acid fraction and concomitant valuable impurities.