Synthesis Of 18C6 Derivatives Functionalized Graphene And The Applications On Removal Of Strontium From Aqueous Solution

Treatment and disposal of high-level waste liquid(HLLW)is one of the key process in nuclear fuel cycle,and it is also a worldwide problem,which is of great significance to the sustainable development of nuclear power.HLLW contains a large number of radionuclides ? Among them,90 Sr with a short half-life is one of the heat emitting nuclides process and is especially harmful for the solidified body.If it can be separated,not only can reduce the volume of solidified body,shorten the cooling time and storage time,but also simplify the geological disposal process,cost savings.Therefore,how to safely and efficiently isolate strontium from high level radioactive waste is one of the challenging topics in nuclear waste disposal.The objective of this paper is that18-crown-6 is functionalized to graphene by chemical method.And the adsorption properties of 18-C-6/GO on Sr(II)were studied.The content is as follow:(1)The amino groups were successfully functionalized onto the benzene ring of benzo 18-crown-6 and dibenzo-18-crown-6 by nitration and ammonization successively.The molecular structure of the intermediates and final products were characterized by FT-IR and ESI-MS.Two type of functionalized GOs were successfully prepared by grafting 18-crown-6 onto the surface of matrix by the condensation reaction of carboxyl group with amino group.The dosage and reaction time of 18-crown-6 were optimized by the amount of 18-crown-6 grafted on the GO.And the surface physical and chemical properties of 18-crown-6 functionalized graphene oxide(AB18C6/GO)and dibenzo-18-crown-6 functionalized graphene oxide(DADB18/GO)has been comprehensively characterized by SEM,TEM,Raman and elemental analysis.The results indicate that the amout grafted on GO is as high as 2.12 mmol/g and 3.11 mmol/g for DADB18/GO and AB18C6/GO,respectively.Additionly,functionalized graphene stillmaintained a good flaky structure.(2)The adsorption performance of 4-aminobenzo-18-crown-6 functionalized graphene as adsorbents to strontium was tested through batch adsorption experiment.The main results are summarized as follows: The optimum acid concentration of the adsorbents for adsorption of strontium was 3 M,and the max adsorption capacity is 37.3mg g-1.The strontium sorption on the adsorbents were well fitted to the pseudo-second kinetics models which indicated that the adsorption processes were mainly controlled by chemical action;And the process could be well defined by the Freundlich isotherm,the monolayer adsorption capacity of the adsorbents increased with increasing temperature and strontium concentration;According thermodynamics study,the strontium adsorption on the adsorbents were all endothermic and spontaneous in nature.Selective adsorption studies showed that the selectivity of the adsorbents for strontium ions was found to be fairly desirable by the sorption tests with the solutions containing a range of competing metal ions.(3)The effects of nitric acid concentration,reaction time,initial concentration of Sr2+,dosage as well as coexisting cations on the adsorption of Sr(II)on AB18C6/ GO and DADB18/GO were investigated systematically.The adsorption kinetics,thermodynamics and isotherms have been also carefully studied.The optimum acidity of solution for adsorption of Sr(II)on AB18C6/GO and DADB18/GO is determined to be 3.0 mol/L and4.0 mol/L,respectively.The adsorption equilibrium time is approximately 36 h and 48 h,respectively.The saturated monolayer adsorption capacity for Sr(II)reaches up to 243.12mg/g and 534.76 mg/g for AB18C6/GO and DADB18/GO.The adsorption processes are in accordance well with the pseduo-second kinetic model and the Freundlich adsorption model,and the chemical binding energy is between 8~16 kJ/mol-1,which means Sr(II)are chemically adsorbed on AB18C6/GO and DADB18/GO.The adsorption thermodynamics suggests that adsorptions are spontaneous in nature and endothermic.Moreover,AB18C6/GO and DADB18 /GO have superior selectivity for Sr(II)in presence of Cu(II),Cs(I),Hg(II),U(VI),Na(I),Ba(II),Ni(II)and La(III).This paper provides a reference for the treatment of heat release elements Sr in high level waste water and also offers a basis for the removal and recovery of other elements in HLLW.