Preparation And Green Application Of Praseodymium Oxide Nanomaterials

Rare earth resources in China are very rich,with many kinds and large reserves.Rare earth elements are widely used because of their unique properties.Because Ce in cerium oxide（Ce O₂）can easily convert between Ce（IV）and Ce（III）oxidation states,the research on rare earth oxides mainly focuses on Ce O₂,and has achieved good results in many fields,which has become a hot spot in recent years.Among all rare earth oxides,praseodymium oxide(Pr₆O₁₁)has the highest oxygen ion mobility,and the oxidation states of praseodymium ions(Pr³⁺and Pr⁴⁺)can change rapidly.Compared with Ce O₂,Pr₆O₁₁ has higher stability at room temperature,and there are many stable phases.Its unique physical and chemical properties have great research space and application prospects.This paper focuses on the preparation and green application of praseodymium oxide nanomaterials.The specific research contents are as follows:（1）Pr₆O₁₁ nanoparticles were synthesized by direct precipitation method and characterized.In order to explore its properties,a series of characterization were carried out.On the basis of these characterization data,the special interaction between Pr₆O₁₁ and H₂O₂was further studied.It was found that the optical properties of Pr₆O₁₁ changed with low concentration of H₂O₂.It was speculated that H₂O₂ covalently bound to the surface of Pr₆O₁₁,resulting in the increase of its absorbance.When Pr₆O₁₁ reacts with medium concentration H₂O₂,the ratio of Pr³⁺and Pr⁴⁺in the product changes,which may result in Fenton like reaction and the formation of negatively charged adsorbed oxygen species.When Pr₆O₁₁reacts with high concentration of H₂O₂,it acts as a catalase and catalyzes the decomposition of H₂O₂ to produce oxygen.（2）According to the excellent photothermal performance of Pr₆O₁₁,the Pr₆O₁₁ was used as the photothermal converter,and the three dimensional mushroom shape porous melamine sponge was used as the water transporter.The Pr₆O₁₁ was modified on the designed melamine sea surface through the adhesion of polydopamine to build an integrated,free floating solar photothermal evaporator based on praseodymium oxide nanomaterials.Clean water can be obtained by converting clean solar energy resources into heat energy and then evaporating water.This process is green and environmentally friendly,with high evaporation rate and good salt resistance.（3）According to the strong oxidation of Pr₆O₁₁ and the special property that praseodymium ion can freely convert between Pr³⁺and Pr⁴⁺,Pr₆O₁₁ is used in the degradation of organic compounds.Praseodymium graphene sodium alginate hydrogel was prepared through the preparation of typical gel of sodium alginate and Ca Cl₂.Sodium alginate hydrogel was used to immobilize the oxidant.The specific surface area of the hydrogel was enhanced by graphene,and the three-dimensional porous honeycomb structure of the hydrogel was maintained to increase the contact area of the reaction and improve the degradation efficiency.The prepared hydrogel not only has good degradation effect for organic matter,but also can be recycled.It has good circulation and storage stability,and can greatly save the cost of oxidant.