Digestion of Low-grade Phosphate ores in Phosphoric acid and Nitric acid

The low-grade phosphate ores with high impurities of sesquioxide were digested in phosphoric acid and nitric acid. The orthogonal test results show that the optimal process conditions: reaction temperature 65 ℃,ratio of liquid to solid 14:1, initial phosphoric acid concentration 20%, nitric acid concentration 9.50 g/L, KDD concentration 5.50 g/L, reaction time 1 hour. The leaching rate of P2O5 is more than 92%, while those of Fe2O3 and Al2O3 are not more than 17%.