Study Onextraction Of Potassium From Phosphate-potassium Ores By Acid Leaching At Low Temperature

Putting the agriculture in the first place of national economy is a basic state policy asthe innegligible food problem with a large population. Nitrogen, phosphorus and potassiumare three kinds of chemical elements which are all essential to the normal growth of crops.However, these are no soluble potassium ore except the Qinghai Lake area. And the ratioof fertilization is unreasonable withabundantnitrogenand deficient potassium andphosphorus. Therefore, there is a serious shortage and huge demand for phosphorus andpotassium fertilizer.In recently years, the phosphorus-potassium ore with enormous quantities in Yilingarea of Yichang City in Hubei Province, including phosphate rock and potash feldspar, hasbeen discovered. This kind of low grade orewith a high impurity SiO2contentincludesaP2O5content of4%to12%and a K2O content of5%to9%. If thepotassium in this kind oflow grade ore could be used fully, there will be a great economic and social benefit.An analysis method of potassium in acid-leaching solution of phosphate-potassiumores from Yiling area is established with standard addition methodsof using atomicabsorption spectrophotometer. Also, the reaction characteristics, resistance to retardency,sulfuric acid leaching process, phosphoric acid leaching process and leaching kineticsmodel of phosphate-potassium ores are studied. Finally, there is a trial carried out withmicrowave heating.The main experimental results are as follows:（1）It was accurate to measure the content of potassium in acid-leaching solutionwith standard addition method of using atomic absorption spectrophotometer (AAS). Itshowed that the standard deviation is less than3%and the recovery rate was97.5%to99.0%. And it met the balance of potassium among the ores, solution and residues.（2） The reaction activity and resistance to retardency of three kinds ofphosphate-potassium ores from Yiling area were high, but the ores foamed seriously.Therefore, the defoamer should be added during the wet process.（3）The potassium leaching rate was obtained to be75.1%in sulfuric acid media when m (phosphate-potassium ore from Taiyangshan): m (calcium fluoride): V (50%sulfuric acid) was1g:1g:3mL at120℃for5hours.The potassium leaching rate wasobtained to be85.6%inphosphoric acid media when m (phosphate-potassium ore fromTaiyangshan): m (calcium fluoride): V (60%phosphoric acid) was1g:0.3g:10mL at110℃and the speed of500r/minfor14hours.（4）SEM analysis showed that the ore became a kind of porous unconsolidatedmaterial after phosphoric acid leaching. XRD analysis showed that acidolysis was the mainchemical reaction in phosphoric acid leaching process.（5）The unsteady-state diffusion model of liquid film was established in phosphoricacid leaching process. There was a good agreement between calculated and experimentalresults. In addition, the calculated activation energy valueby the Arrhenius’ equationwas11.68kJ/mol.（6）The exploration of the microwave experiments showed that the leaching speed ofpotassium is very fast and microwave heating has a certain enhancement comparing withconventional heating.