Study On The Separation Of Al³⁺ And Mg²⁺ In Phosphate Rock Acid Hydrolysis Solution

At present,wet-process phosphoric acid process has become the main way to produce phosphoric acid worldwide,and 80%⁹0%of phosphoric acid production is obtained by it.In spite of that,some problems,such as the difficulty to purify impurity ions during this process,considerably restrict its further application.In this paper,phosphate Weng’an county of Guizhou Province as the raw material,Mg²⁺and Al³⁺in phosphate leach solution are separated and studied.In a simulated acidic system（PH=-0.36）,the initial concentration of magnesium ions and aluminum ions are 0.7605g/L and 0.5589g/L,respectively.Then,Al³⁺is separated by chemical precipitation method while solvent extraction method and emulsion liquid membrane method are adopted to separate Mg²⁺.This research has achieved efficient extraction of magnesium ions and aluminum ions under the condition of high acidity,which is of great value for the purification of wet-process phosphoric acid.When ZX-1 is used as precipitant to remove aluminum ions in phosphate leach solution,the effects of different pH value,dosage of precipitant,temperature and reaction time on the effect of precipitation and removal of aluminum are investigated to obtain the optimal process conditions.The results show that when the PH of phosphate leach solution is 2 and the amount of ZX-1 is 1.5g,after 8 hours’reaction at room temperature（20℃）,the removal rate of aluminum ions can reach 65.38%.And the recovery rate of P₂O₅ in the phosphate leach solution is higher than 99%.Under the hydrochloric acid system,emulsion liquid membrane（ELM）is used to separate magnesium ions from phosphate leach solution with high acidity.The ELM is prepared using ZX-2 as carrier,polyisocrotyl succinimide（T154）as surfactant and HCl as internal phase,and then is diluted with sulfonated kerosene.Research is focused on the types and concentrations of carrier and surfactant,the acidity of the internal phase,volume ratio of organic phase to internal phase and volume ratio of the emulsion phase to the solution.The results demonstrate that when the solution with the optimum condition contains of 12%ZX-2,8%T154,80%sulfonated kerosene as organic phase,8mol/L HCl as internal phase,1:1 volume ratio of organic phase to internal phase,1:5 volume ratio of the emulsion phase to the feed solution,the extraction rate of magnesium ions can reach 51.96%.And the recovery rate of P₂O₅ in the phosphate leach solution is higher than 98%.The extraction of magnesium ions in phosphate leach solution is studied by solvent extraction,using ZX-3 as complex extractant under the condition of pH=-0.36.The effects of diluent types,extraction time,concentration of the complex extractant and phase ratio of oil phase over aqueous phase（O/A）on the extraction rate of magnesium ions are investigated.The results indicate that when sulfonated kerosene is used as the diluent,the concentration of ZX-3 and sulfonated kerosene is30%and 70%respectively,O/A=2:1,and 20min of extraction time,a high extraction rate of magnesium ions,about 63.56%,is achieved,accompied by 99%recovery rate of P₂O₅ in phosphate leach solution.At the same time,hydrochloric acid is used as the anti-extractant,and when the concentration of hydrochloric acid is 6mol/L,the anti-extraction rate of magnesium ions can reach 50.11%.