Potassium Extraction From Phosphorus-potassium Associated Ore In The Mixed Solutions Of Phosphoric Acid And Hydrochloric Acid

Potash fertilizer is needed in the growth process of farm crops.At present,the global production of potash fertilizer is primarily based on soluble potassium resources.While the soluble potassium resources are rare in China,the insoluble potash ores,such as K-feldspar?KAl Si3O8?are very abundant.Therefore,the economic and effective extraction of potassium from the insoluble potassium deposit has become an urgent issue.In recent years,the phosphorus-potassium associated ore with a reserve as much as 800 million tons was found in Yichang city,China.The phosphorus-potassium associated ore generally contains relatively 6¹2% P₂O₅ and 5⁹% K2 O contents.The simultaneous extraction of phosphorus and potassium to produce PK compound fertilizer,urgently needed in China,will alleviate the PK compound fertilizer supply problem.The previous research results have shown that the leaching rate of potassium from phosphorus-potassium associated ore in hydrochloric acid solution can reach 90%.However,the higher chlorine and lower phosphorus contents in leaching solution result in the subsequent removal of chloride and production of qualified NPK compound fertilizer extremely difficult.In order to reduce chlorine and increase phosphorus contents in the leaching solution,the use of the mixture of hydrochloric acid and phosphoric acid to leach potassium from phosphorus-potassium associated ore is of great interest.The main research contents and conclusions are as follows:?1?The extraction of potassium from phosphorus-potassium associated ore in the mixture of hydrochloric acid and phosphoric acid was studied.The effect of the mode of addition of hydrochloric acid,the mass fraction of hydrochloric acid,temperature,solid-to-liquid ratio and Ca F2 dosage and stirring speed on the leaching rate of potassium were investigated.The results show that the mode of addition of hydrochloric acid has insignificant influence,while the mass fraction of hydrochloric acid,temperature,solid-to-liquid ratio and Ca F2 dosage have obvious influence on the leaching process.An orthogonal regression design was used to optimize the leaching process and an a regression model was established.This model predicted that under the optimal solution of the hydrochloric acid mass fraction 10%,solid-to-liquid ratio of 1/5,the addition of 2 g Ca F2 and the temperature of 95 °C.At this point,the leaching rate of potassium can be reached85% which basically agreed with the experiment result.?2?Semi-empirical kinetic equations based on the shrinking unreacted-core model were established to express the leaching kinetics of potassium from phosphorus-potassium associated ore in the mixture of hydrochloric acid and phosphoric acid.The experimental data involving the factors of mass fraction of hydrochloric acid,solid-to-liquid ratio,Ca F2 dosage and temperature were fitted by internal diffusion-control and chemical-control equations,respectively.The results show that the product layer diffusion-control equation has higher fitting degree,and the equation can be written as follows:The determined apparent activation energy of the leaching process is 54.67 k J mol-1.?3?The effect of surfactant addition on the leaching rate of potassium from phosphorus-potassium ore under the optimal condition was investigated.The results show that the leaching rate of potassium increased by 10%-15% and reaches to 95.01% by adding anionic surfactant?SDS and SLS?,the leaching rate of potassium decreases by adding cationic surfactant?CTAC?and nonionic surfactant?PEG-6000 and PEG-10000?.