Research On The Preparation Of Rare Earth Oxides By Electrolysis Of Rare Earth Chloride Aqueous Solution

As well known as industrial "gold",rare earth elements have excellent physical properties,such as optical,electricity and magnetic,which can,together with other materials,be composed of a variety of new materials with different properties,so that they are widely used in many fields:the petroleum chemical industry,glass ceramic,metallurgy,machinery,and other areas of the traditional industries,as well as the catalytic,polishing,magnetic materials.At present,the main intermediate product,which is formed in the process when preparing of rare earth oxides from rare-earth ore,is the solution of rare earth chloride.Currently,the main treatment of rare earth chloride solution is precipitation,which has two major deficiencies:a large amount of ammonium nitrogen waste liquid discharged and low purity of products.To solve the problems,the idea proposed in this paper is that the technology of ion membrane electrolysis in chloro-alkali industry is applied to the preparation of rare earth oxides,and a new method is put forward to prepare rare earth oxides by electrolysis of rare earth chloride aqueous solution,which meanwhile provides some theory and data foundation for the green production of rare earth oxides.The conclusions of this study are as follows:(1)the products formed by electrolysis of LaCl3 aqueous solution directly is La(OH)3,while,the product generated by electrolysis of CeCl3 aqueous solution directly is CeO2;when the conditions of electrolysis of LaCl3 aqueous solution and CeCl3 aqueous solution are that current density is 100 mA/cm2,initial concentration of electrolyte is 0.3～0.5 mol/L(that of CeCl3 is 0.5 mol/L),45～55℃,electrode distance is 2 cm,the electrolysis time is 25 min(that of CeCl3 is 30 min),the current efficiency of LaCl3 electrolysis and CeCl3 electrolysis can reach 97.5%and 89.0%,respectively.Besides,when the concentration of electrolyte is lower than 0.3 mol/L,to increase cathode concentration is beneficial to the improvement of current efficiency.(2)La(OH)3 is prepared from LaCl3 aqueous solution by electrolysis directly,and the results show that:the chlorine ion mass fraction of the product(La(OH)3)is lower than 0.040%,and the product calcined at 800℃ for 1.5 h is La2O3,whose D0.5 is 18～46 μm and the chlorine ion mass fraction is lower than 0.01 8%.In addition,the products of LaCl3 electrolysis with CO2 are mixtures,and the product calcined at 800℃ for 1.5 h is La2O3,of which the chlorine ion mass fraction is lower than 0.028%,and D0.5 is about 16 μm.(3)CeO2 is prepared from CeCl3 aqueous solution by electrolysis directly,and the results show that:the chlorine ion mass fraction of the product is lower than 0.020%,and D0.5 is 10～30μm.The product calcined at 800℃ for 1.5 h is CeO2,of which the chlorine ion mass fraction is lower than 0.018%,and D0.5 is about 20～40 μm.