Study On The Separation And Preparation Of Rare Earth Oxides From Bastnaesite By Liquid Phase Method

Bastnaesiteis a very important light rare earth minerals in our country.At present,the main method of treatment of bastnaesite is “oxidation roasting-acid leaching process”.Ce?III?in minerals is oxidized to Ce?IV?by oxidation roasting,And then using CeO2 insoluble in the characteristics of dilute acid in acid leaching process of roasted ore.After the acid leaching and filtration,rich cerium rare earth acid leaching residue and less cerium rare earth acid leaching solution were obtained,This process of one step separation of cerium and other trivalent rare earth elements are often impure separation,The leaching residue of cerium rich rare earth needs further alkali conversion,Consuming a large amount of alkali,At the same time the high value of rare earth in slag can not be fully utilized,resulting in a waste of rare resources.In this paper,NaHCO₃ was used as the roasting additive,Focusing on bastnaesite oxidation roasting-dilute hydrochloric acid leaching process,For the research purpose of improving the leaching rate?recovery rate?of rare earth,By chemical precipitation method extracting and separating of rare earth elements from rare earth acid leaching solution and the rare earth precipitate precursor was obtained,After roasting heat treatment to obtain rare earth oxides.The calcinations and decomposition stage of bastnaesite,NaHCO₃ was used as decomposition assistant,The results show that: there will be molten liquid phase when the calcination temperature is above 723 ?,The oxidation of Ce?III?can be effectively inhibited by the inclusion of mineral powder particles in molten phase,Ce?III?follows other trivalent rare earth into the acid leaching solution in the process of acid leaching,To achieve the purpose of improving the leaching rate rare earth.The process of decomposition,washing and hydrochloric acid leaching of bastnaesite was studied in detail.The experimental results show that: the addition of NaHCO₃ is 40%,roasted at 900 ? for 2 h;Water washing temperature at 50 ?,the ratio of liquid to solid is 10:1;the acid leaching conditions: the hydrochloric acid concentration,the ratio of liquid to solid,the leaching temperature,and the leaching time are 2 mol/L,15:1,75 ?,2 h,respectively.Under this optimized condition: the removal rate of F-was 83.57%,the leaching rate of Ce was 87.43%,the leaching rate of total rare earth was 91.74%.Extraction and Separation of Rare earth elements from enriched Rare Earth acid leaching solution by chemical precipitation method,The experimental results show that: NH3·H2O precipitation,regulating solution pH=9,75 ? for 2 h,The total rare earth recovery rate is 67.68%;H2C2O4 precipitation,The concentration of H2C2O4 is 0.5 mol/L,75 ? for 0.5 h,The total rare earth recovery rate is 82.65%,The precursor of rare earth precipitation has the highest crystallinity and high purity;NH4HCO₃ precipitation,The concentration of NH4HCO₃ is 0.75 mol/L,25 ? for 1.5 h,The total rare earth recovery rate is 64.55%.The rare earth precipitated precursor was calcined at 800 ? for 2 h,and the products are mixed rare earth oxides.The morphology of the mixed rare earth oxide is spherical by NH3·H2O,The particle size is 2³ nm,but the reunion is serious,the REO is up to 90.71%;The morphology of the mixed rare earth oxide is also spherical by NH4HCO₃,The particle size is 100²00 nm,The spherical particles are uniformly distributed and closely connected to form a pore network structure,the REO is up to 94.24%,The crystallinity of mixed rare earth oxides obtained from H2C2O4 is the best,the REO is 94.24%,The morphology is blocky,The particle size: The length is about 3 um,the width is about 0.75 um.