Polymer-functionalized MoS₂ Sheets For Efficient Sorption Of Uranium And Europium

Nuclear energy is one of the three pillars of the world's energy supply,which can provide large-scale and stable energy,and reduce carbon dioxide and pollutant emissions effectively.However,large quantities of radioactive waste will be produced in the process of power generation and uranium mining,which will threaten global environment and human health if not being properly treated.Uranium is the main element of nuclear fuel cycle,and other lanthanides and actinides have long-term hazards to the entire biosphere as well.Europium is usually considered as a homologue for trivalent lanthanides and actinides because of the similar ionic radius between each other,which results in the similar physicochemical behavior.Therefore,the development of novel material and technique is of great importance for efficient removal of uranium and europium.The layered sulfide sorbents exhibit excellent ability to bind with metals due to the covalency between the metals and sulfur.Many progresses have been made in layered sulfides for rapid sorption of uranium and other heavy metals.In this paper,we synthesized polymer ligands functionalized MoS₂ sheets composite materials to explore their application in uranium and europium sorption.Specific studies of this paper are as follows:?1?Amidoximated poly?vinyl imidazole?-functionalized MoS₂ sheets for efficient sorption of a uranyl tricarbonate complex from aqueous solutionsIn order to synthesize amidoximated poly?vinyl imidazole?-functionalized molybdenum disulfide sheets?MoS₂-PVIAO?,MoS₂-sheets were first prepared by intercalating exfoliation of MoS₂ powder with n-butyllithium,and amidoximated poly?vinyl imidazole??PVIAO?was synthesized by controlled polymerization of vinyl imidazole and subsequent reaction with 4-bromobutyronitrile and hydroxylamine,respectively.MoS₂-PVIAO was then prepared by grafting PVIAO onto MoS₂-sheets in the presence of n-butylamine.During the reaction,the terminal trithiocarbonate groups of PVIAO chains were converted into thiol groups,and the chains could connect with vacancy defects of exfoliated MoS₂-sheets through disulphide bonds.Successful synthesis of MoS₂-PVIAO was verified by FT-IR spectra,XPS spectra and etc.The graft degree of PVIAO could reach 53.7%calculated by thermogravimetric analysis.The effects of sorbent dose,contact time,coexisting ions and salinity on uranium sorption were studied.The sorption followed pseudo-second-order kinetics model with large rate constant,and the equilibrium could be reached within 30 s.The maximum sorption capacity could reach 348.4mg/g at pH 8.0 and 298.15 K.The MoS₂-PVIAO showed higher selectivity towards uranium over coexisting ions in comparison with MoS₂-sheets.In addition,the sorbent exhibited remarkable salt-resistant stability and could be regenerated efficiently after five cycles with high efficiency.As far as we know,this is the first report on MoS₂-sheets for sorption of radionuclides from aqueous solution.This work demonstrates that MoS₂-sheets can be used as the promising materials for the separation of radionuclide from aqueous solution.?2?Poly?4-vinylbenzylphosphonic acid diethyl ester-co-maleic anhydride?functionalized-MoS₂ sheets for uranium and europium sorption from aqueous solutions.4-Vinylbenzylphosphonic acid diethyl ester monomer was synthesized and verified by NMR,and then poly?4-vinylbenzylphosphonic acid diethyl ester-co-maleic anhydride??PDMA?was synthesized by controlled radical polymerization.4-vinylbenzylphosphonic acid diethyl ester and maleic anhydride copolymer functionalized-molybdenum disulfide sheets?MoS₂-PDMA?was prepared according to the method of previous section.Successful synthesis of MoS₂-PDMA was verified by FT-IR spectra,XPS spectra,and etc.The graft degree of PDMA was27.3%calculated by thermogravimetric analysis.The effects of p H,contact time and initial concentration on uranium and europium sorption were studied.The sorption followed pseudo-second-order kinetics model with large rate constant,and the equilibrium could be reached within 60 min.The maximum sorption capacity of uranium and europium could reach 448.4 mg/g and 171.2 mg/g at pH 4.0 and 298.15K,respectively.The sorbent could be regenerated efficiently after five cycles with high efficiency.XPS spectra showed that the sorption of uranium and europium on the sorbents were attributed to the interaction between sulfur,O=C-O,P-O and uranium/europium.This work demonstrates that MoS₂-PDMA can be used as the promising materials for the separation of radionuclide from aqueous solution.