RI 8061 Fluosilicic Acid Acidulation of Phosphate Rock

The Bureau of Mines conducted pioneering batch and laboratory cyclic tests that simulated plant operation in developing a procedure for acidulating phosphate rock with fluosilicic acid. Both high-grade deslimed phosphate rock and low-grade phosphate rock samples were treated. The most promising results were obtained by acidulating des limed high-grade material. In a series of seven cyclic tests, 85.4 percent of the P20S was recovered in solutions. The average P2O5 content of the phosphoric acid-monocalcium phosphate solutions of the first step was 156 grams per liter, and the average fluorine content was 4.7 grams per liter. Residues had an average fluorine content of 30.7 percent and contained 83.9 percent of the total fluorine in the charge materials. Some fluorine was lost by volatilization.