Selective Actinide Separation By Magnetic Nanoparticles Functionalized With Switchable Chelators

As the application of nuclear industry and nuclear energy technology,Nuclear waste is increasing year by year.As we all know,nuclear waste is a huge hazard to the entire human population and even the ecological environment.At present,there are certain shortcomings in the treatment of nuclear waste.Therefore,Janus nanoparticles functionalized with multiple on-demand cleavable ligands for actinides separation will be used to separate radioactive elements from high level radioactive nuclear waste liquid.Firstly,iron oxide super-paramagnetic nanoparticles??-Fe₂O₃?with a diameter of about 7.3 nm were prepared by coprecipitation method.Then,the surface of?-Fe₂O₃ nanoparticles were coated with polyacrylic acid with a thickness of about 5 nm.Subsequently,type A nanoparticles,iron oxide nanoparticles coated with PAA and functionalized with DTPA chelator(?-Fe₂O₃-PAA_2K-DTPA),were synthesized with an average number of 18.9 DTPA per nanoparticle.In these particles,DTPA is connected to nanoparticles core by a disulfide bridge.The DTPA chelator has been successfully released from the particles by increasing the p H to 9.?-Fe₂O₃-PAA_2K-DTPA are able to chelate La³⁺ions and the DTPA-La³⁺complexes can be efficiently released from the particles in alkaline p H.Secondly,as required for the creation of type B nanoparticles,a novel actinide chelator based on the architecture of DMOGA?a chelator used in TRPO process for selective separation of Uranium?was synthesized.This new chelator,named FHECMAA,owns a furan group which will be exploited in its further covalent couplings to nanoparticles.The FHECMAA chelator has been coupled to nanoparticles via Diels-Alder reaction.?-Fe₂O₃-PAA_2K-FHECMAA can adsorb uranyl ions.Chelation of Uranium containing species and release of FHECMAA-U complexes after heating has been made by retro-Diels-Alder reaction.Finally,Janus nanoparticles(?-Fe₂O₃-PAA_2K-DTPA-FHECMAA)were synthesized by"masking"method based on the experience of synthesis of type A and B nanoparticles.Janus particles having one different type of chelator on each face.Control of chelators release is optimal,as DTPA was not detach when FHECMAA was,and vice versa.UV-vis analysis show that,in average,each nanoparticles is functionalized with 49.8 DTPA chelators and 27.6 FHECMAA chelators.At p H=3,both types of chelators have extracted the same ratio of La and U?about 55%/45%?.At p H=7,separation works much better as DTPA showed a very good affinity for La³⁺with ratio of La/U equals to 82.7%/27.3%.Moreover,FHECMAA showed a quite good affinity for Uranium?La/U=68.7%/31.3%?regarding to the rarity ofand Uranium based cations at neutral p H.These resultssuggestthatJanus?-Fe₂O₃-PAA_2K-DTPA-FHECMAA nanoparticles are good candidates for the separation of Uranium and trivalent cations in ground water surrounding nuclear waste repository.