Preparation And Photocatalytic Properties Exploration Of Cerium Lanthanum Rare Earth Oxides

As the largest proven reserve among all rare earth?RE?minerals in the world,bastnasite is one of the most industrial application value rare earth minerals.Currently,Na₂CO₃ or NaHCO₃ is used as the processing aids in roasting decomposition of bastnaesite.The main rare earth elements in bastnaesite are cerium and lanthanum,but complete separation of the two rare earth elements is difficult due to the nature close.Extracting rare earth elements separately is difficult and costly.Therefore,using bastnaesite as raw material,cerium and lanthanum always mixed together whether extracting rare earth elements from the extraction slag or extraction liquid.Accordingly,one purpose of this work is to study the roasting decomposition of bastnaesite to make better use Bastnasite to extract the cerium lanthanum rare earth oxides,the other is to prepare the cerium lanthanum rare earth oxides with different materials and study their photocatalytic properties.To study the decomposition of bastnaesite,firstly,we calculated decomposition activation energy of bastnaesite,bastnaesite+Na₂CO₃ and bastnaesite+NaHCO₃according to the thermal analysis?TG-DTA?results.The activation energy ranges of bastnaesite,bastnaesite+Na₂CO₃ and bastnaesite+NaHCO₃ were 163.33¹77.79kJ/mol,77.80⁹1.17kJ/mol,and 113.23¹70.55kJ/mol,respectively.The effect of baking aids were studied by phase analysis?XRD?,elemental analysis?XRF?and other methods.The result showed that both Na₂CO₃ and NaHCO₃ can promote decomposition of rare earth carbonate and sulfate of alkaline earth metal in bastnasite,however,NaHCO₃ was more effective than Na₂CO₃ in removing F at high temperature?900??.Cerium lanthanum rare earth oxides were synthesized by hydrothermal method using Ce?NO₃?₃·6H₂O,La?NO₃?₃·6H₂O as raw materials.The crystallinity of CeO₂was enhanced with higher hydrothermal reaction temperature,however,the transition from RE?OH?₃ to CeO₂ was prohibited by adding lanthanum.Moreover,the morphology of products transformed from nanocube to nanorods with the increasing of lanthanum doping.After 400?/2h heat treatment of the hydrothermal products,La³⁺can be doped into CeO₂ lattice and formed pure phase.The band gap of cerium oxide was reduced by La³⁺doping,and the absorption range red-shifted from ultraviolet region to visible region.The 50%La³⁺doped CeO₂ showed the greatest red-shift cutoff wavelength?⁴70nm?and the widest range of absorption?200nm⁴70nm?.The cerium lanthanum rare earth oxides obtained at 180?/8h hydrothermal reaction showed good photocatalytic properties on degradation of Methylene Blue.Cerium lanthanum rare earth oxides were obtained using the leachate extracted from bastnaesite as raw materials and NaOH as precipitant,under the similar hydrothermal condition and post heat treatment process.The total rare earth oxides content was 80.43%in the product,and Ce/La molar ratio was 1:0.89.The phase and morphology of the product was similar with the rare earth oxides prepared by chemical reagent,however,the energy band gap?2.95eV?was smaller than that of the product?3.04eV?prepared from chemical reagents,and 0.37eV lower than pure CeO₂?3.32eV?.The absorption range of light red-shifted from the ultraviolet to visible?⁷00nm?.Under the same hydrothermal preparation conditions,the photocatalytic properties of cerium lanthanum rare earth oxide obtained from bastnaesite was superior to that from chemical reagents,which provided a promising application of bastnaesite.