Study On Permeability Of Modified Graphene Oxide Films To Metal Ions In Radioactive Wastewater

With the development of nuclear energy,the treatment of radioactive wastewater become an urgent problem to be solved.The purification of radioactive wastewater is more challenging than the treatment of industrial and municipal wastewater.Among the various methods of traditional technologies on radioactive wastewater,membrane separation technology plays an important role by virtue of its advantages of no chemical additives,low energy comsumption,renewable and reusable.Graphene and its derivatives are natural two-dimensional materials that can be used as new membrane materials in the field of water separation.However,the hydration radius of main ions in radioactive wastewater was significantly difference,GO membrane could be used to separate metal ions.Their permeation behavior in radioactive wastewater on GO membrane was investigated.In this paper,two kinds of high stability filtration membrane?GO-Ma and GO-Ad?were prepared by dicarboxylic acid?malonate Ma and adipic acid Ad?crosslinked with graphene oxide?GO?.GO-Ma and GO-Ad were characterized by SEM,XRD,FTIR and XPS.The water flux of GO-Ma and GO-Ad was measured.The rejection rates of main group metal ions and heavy metal ions were studied.The permeability of seven metal ions?Ni,Cu,Zn,Cr,Cd,Pb,As?in simulated radioactive wastewater through GO-Ma membrane was explored.The results showed that the water fluxes of GO-Ma and GO-Ad are 6.63 and 11.76 L·m^-2·h^-1·bar^-1,respectively.The rejection rates of K⁺,Na⁺,Ca²⁺reached over 83.5%?GO-Ma?and 79.4%?GO-Ad?,respectively.Meanwhile the rejection rates of Zn²⁺,Cd²⁺,Pb²⁺were 90.15%?GO-Ma?and 88.16%?GO-Ad?.There was good property to block metal ions?Ni,Cu,Zn,Cr,Cd,Pb,As?in the simulated wastewater through GO-Ma.GO-Ma can be used repeatedly by simple acid washing.These results indicated that GO-Ma and GO-Ad had potential applications in radioactive wastewater treatment.In this chapter,GO-CNT composite membranes were prepared by acid-oxidized carbon nanotubes?CNT?cross-linked with graphene oxide?GO?,and their structures were characterized by SEM,FTIR,XRD and XPS.The effects of CNT doping amounts,acidity and ionic strength to UO₂²⁺rejection were explored.The results showed that the interlayer spacing increases with CNT doping amounts increases and the rejection rates of UO₂²⁺decreases.The permeate amounts decrease with ionic strength increase and acid concentration decrease.The membrane keeps excellent recycle by acid washing.GO-CNT-Me was prepared by using melamine?Me?and acidic oxidized carbon nanotubes?CNT?to modify graphene oxide?GO?membrane.GO-CNT-Me was characterized by SEM,XRD,FTIR and XPS.The permeability of metal ions was studied through GO-CNT-Me.GO-CNT-Me has a large interlayer spacing characterized by XRD.The permeate results showed that the permeability of alkali metals?Na⁺,K⁺,Cs⁺?was over 26.61%,alkaline earth metals(Mg²⁺,Ca²⁺,Sr²⁺)was14.34%and transition metals(Zn²⁺,Cd²⁺,Pb²⁺)was greater than 11.6%.The permeate rate of UO₂²⁺was 8.26%when there was K⁺,Ca²⁺in the solution through GO-CNT-Me and the separation ratio of K⁺to UO₂²⁺is 3.24.GO-CNT-Me has the potential to separate UO₂²⁺from monovalent and divalent metal ions.