Experimental Research of Preparation of Phosphoric Acid from Low-Grade Phosphate Rock

As the phosphate rock resources exhausts gradually in the world,exploiting and utilizing low-grade phosphate rock is becoming very pressing.This study adopts nitric acid to decompose low-grade phosphate rock.Aiming at the improvement of the extraction rate of P2O5 from phosphate rock,the mass fraction of nitric acid,acid ratio,reaction temperature and reaction time are researched.The optimum technological conditions of using nitric acid to dissolve low-grade phosphate rock are thus obtained: the mass fraction of nitric acid is 29%,acid ratio 8,the temperature of reaction 60℃ and reaction time 45 min.With these optimum conditions,the extraction rate of P2O5 from phosphate rock reaches 98.1%.Scanning election microscope is then employed to observe the changes of morphology characteristics in the surface of phosphate rock at different reaction time.The experimental results provide the basic data and feasibility analysis for preparing phosphoric acid by using two-step method to decompose low-grade phosphate rock and jointly produce calcium sulfate whisker.