Study on leaching rate of calcium and magnesium from phosphorus tailings based on thermodynamic analysis and response surface method
In the recovery of calcium and magnesium resources in phosphorus tailings,the tailings are usually calcined firstly,and then the calcium and magnesium in the tailings are leached by leaching process for subsequent resource recov-ery.In the calcination process,it is necessary to decompose dolomite in phosphorus tailings as much as possible,while the fluorine apatite is retained.In this study,HSC Chemistry software was used to conduct thermodynamic analysis of calcina-tion of phosphorus tailings to optimize calcination conditions.In the process of leaching calcium and magnesium from tail-ings calcined,based on response surface method,the interaction effects of ammonia-calcium mole ratio(7∶1～11∶1),liquid-solid mass ratio(7∶1～9∶1),reaction temperature(60～80℃)and reaction time(50～70 min)on the leaching rate of calcium and magnesium were analyzed,and the leaching conditions were optimized.The results showed that the calcination tempera-ture range of the dolomite completely decomposed into CaO and MgO and the fluorapatite undecomposed range was(900～1 200℃).The optimal leaching rates of calcium and magnesium were 92.25%and 86.19%when ammonia-calcium mole ra-tio was 10∶1,liquid-solid mass ratio was 8∶1,reaction temperature was 71℃and reaction time was 66 min,respectively.According to the optimized leaching conditions,several experiments were carried out,and the experimental results showed that the leaching rate of calcium was 91.95%and that of magnesium was 85.85%.The experimental results were close to the optimization results,which proved that the optimization results were more accurate,and through simulation optimization and experimental verification,it could be seen that the ammonium-calcium ratio had a greater impact on the leaching rate.
phosphorus tailingsthermodynamic analysisresponse surface methodcalcium and magnesium leachingcal-cination
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