Phosphate recovery by acid retardation
A method of recovering phosphoric acid from process water includes directing a process water stream having a pH and a first concentration of phosphoric acid and at least one salt into a vessel, contacting the process water stream with a sorption agent in the vessel, the sorption agent adsorbing phosphoric acid from the process water, withdrawing a first effluent including a first concentration of the at least one salt and a second concentration of phosphoric acid from the vessel, and contacting the sorption agent including the phosphoric acid with water, at least a portion of the phosphoric acid desorbing from the ion exchange media into the water to form a second effluent having a third concentration of phosphoric acid.
1. A method, comprising:
directing a process water stream having a pH and a first concentration of phosphoric acid and at least one salt into a vessel;
controlling the pH of the process water stream by the addition of an acid and/or a base to a pH of about 2 to about 3 ;
contacting the pH-controlled process water stream with a sorption agent comprising a strong base anion exchange resin in the vessel, the sorption agent adsorbing phosphoric acid from the pH-controlled process water stream;
withdrawing a first effluent including a first concentration of the at least one salt and a second concentration of phosphoric acid from the vessel; and
desorbing at least a portion of the phosphoric acid from the sorption agent by contacting the sorption agent with water for a period of time effective to form a second effluent having a third concentration of phosphoric acid and a phosphoric acid purity of greater than about 80%.
2. The method of claim 1 , wherein the third concentration of phosphoric acid is higher than the second concentration of phosphoric acid.
3. The method of claim 1 , wherein the at least one salt comprises one of a sulfate and a hexafluorosilicate.
4. The method of claim 1 , further comprising concentrating the phosphoric acid in the second effluent by reverse osmosis.
5. The method of claim 1 , further comprising concentrating the phosphoric acid in the second effluent by evaporation.
6. The method of claim 1 , further comprising recycling at least a portion of the first effluent into the vessel.
7. The method of claim 6 , further comprising combining the at least a portion of the first effluent with the pH-controlled process water stream.
8. A method, comprising:
directing a process water stream having a pH and a first concentration of phosphoric acid and at least one salt into a vessel;
controlling the pH of the process water stream by the addition of an acid and/or a base to a pH of about 1 to about 1 . 5 ;
contacting the pH-controlled process water stream with a sorption agent comprising a strong base anion exchange resin in the vessel, the sorption agent adsorbing phosphoric acid from the pH-controlled process water stream;
withdrawing a first effluent including a first concentration of the at least one salt and a second concentration of phosphoric acid from the vessel; and
desorbing at least a portion of the phosphoric acid from the sorption agent by contacting the sorption agent with water for a period of time effective to form a second effluent having a third concentration of phosphoric acid.
9. The method of claim 8 , wherein the third concentration of phosphoric acid is higher than the second concentration of phosphoric acid.
10. The method of claim 8 , wherein the at least one salt comprises one of a sulfate and a hexafluorosilicate.
11. The method of claim 9 , further comprising concentrating the phosphoric acid in the second effluent.
12. The method of claim 8 , further comprising combining the at least a portion of the first effluent with the pH-controlled process water stream.
13. The method of claim 8 , wherein the second effluent has a recovered phosphoric acid concentration of up to about 2% by weight.