Study On Extraction Of Rare Earth From Sulfuric Acid Decomposing Phosphate Ore System

Phosphorite is rich in rare earth resources.In the process of actual wet-process phosphoric acid production,the rare earth leaching rate is low,and its extraction effect is not ideal.Rare earth,especially the rare earth recovered from phosphorite,plays a vital role in China's economic and technological development.Therefore,this paper studies the mineralogical characteristics of rare earth-bearing Zhijin phosphate ore in Guizhou and the effect of calcium sulfate crystallization on the process of leaching rare earth in the sulfur and phosphorus acid hydrolysis,and analyzes the existence of rare earth in phosphogypsum and the use of emulsion liquid membrane separation technology to extract the rare earth from the actual phosphorite acid solution,and provide the theoretical basis for the comprehensive recovery of rare earth-bearing phosphorite in China.The mineral composition and chemical composition of Zhijin phosphorite are analyzed.The results show that the mineral composition of phosphate ore is dominated by dolomite,quartz,fluorapatite and calcite,and there are micro constituents of pyrite,clay mineral and barite.The phosphate ore belongs to the middle-lower grade in the classification of phosphate ores,in which the content of P₂O₅ is 19.45% and the rare earth is 0.678mg/g which is mainly consisted of Y,La,Ce and Nd.The acid hydrolysis experiments of Zhijin phosphate containing rare earth are carried out by using the sulfur and phosphorus acid hydrolysis.The results showed that the mass fraction of the crystal is 15%,the stoichiometry ratio is 1.10,the volume fraction of the phosphoric acid is 20%,the temperature is 75?,liquid-solid ratio of 4:1,and the mass fraction of polyethylene glycol 4000 is 0.2%,the average particle size and the length to diameter ratio of the calcium sulfate crystal are 6.72?m and 5.9,respectively,and the rare earth leaching rate is 55% in the solution as well.the greater both of the average particle size and the length diameter ratios of the crystals,the higher the rare earth leaching rate.the smaller both of the average particle size and the length diameter ratios of the crystals,the lower the rare earth leaching rate.Hydrochloric acid was used to carry out cyclic washing experiments on phosphogypsum.The results showed that the leaching rate of rare earth is 20.7% under the condition of hydrochloric acid concentration of 1mol/L,liquid to solid ratio of 10:1?hydrochloric acid: phosphate ore?and washing times of 6 times.The rare earth ions in phosphogypsum mainly exist in absorption forms.Since the flow carrier in emulsion liquid membrane process cannot extract the rare earth efficiently in the high acidity environment,the modified extractant P204 is modified and used as a flow carrier to extract the rare earth in the actual acid phosphate solution?pH=-0.3?with strong acid.The results showed that under the following conditions: the concentration of flow carrier P₂0₄-A is 12%?volume fraction,same below?,the surfactant T154 8%,the sulfonated kerosene 80%,the internal water HCl was 8mol/L,Oil-inner ration Roi 1:1,emulsion making time 20 min,the emulsion stirring speed 3000r/min,the ratio of emulsion and water Rew 1:10 and the extraction time 20 min,the extraction rate of rare earth can reach 78.46%.The emulsions obtained by the best technological conditions are demulsified by physical demulsification?heating,centrifugation,ultrasonic?,chemical demulsification and heating–centrifugation combined with demulsification.The results showed that the best demulsification method was the combination of heating and centrifugation combined with demulsification.Under the conditions of heating temperature of 90?,heating time of 120 min,centrifugal speed of 16000r/min and centrifugation time of 30 min,the breaking rate can reach 64%.