| Tritiated wastewater treatment and tritium resources recovery are critical to ensuring the safe operation of nuclear power plants and the stable supply of tritium resources.The previous studies showed that graphene has high potential in efficient tritiated wastewater treatment because of its good separation performance of protium/tritium(H/T)with high efficiency and low energy consumption.In this thesis,the monolayer graphene film and graphene nano sheet were introduced into the solid polymer(SPE)electrolytic cell to carry out the experimental study on tritiated water electrolytic enrichment(i.e.tritium enrichment).The effects of different factors were studied to analyze the H/T separation performance of graphene composite membrane,such as electrolytic current,tritiated water enrichment factor,tritiated water specific activity and graphene loading.The main conclusions are as follows:1)The graphene transfer quality of four different graphene composite membrane preparation processes,including vacuum hot pressing,thermal release tapes transfer,spraying and blending pouring,were studied to prepare large-area graphene composite membrane.The results showed that:i)For the transfer of monolayer graphene,the thermal release tapes transfer process is good to get high graphene quality and to control the composite membrane area,and more suitable for the transfer of monolayer graphene compared with the vacuum hot pressing process.ii)For graphene nano sheet transfer,the spraying method and blending pouring method can easily distribute graphene with controllable area evenly both on the surface and inside of ion exchange membrane respectively.iii)Based on the above analysis,the monolayer graphene composite membrane was prepared by thermal release tapes transfer process.Two kinds of proton graphene composite membranes and two kinds of basic graphene composite membranes were prepared by spraying method and blending pouring method,respectively.2)The H/T separation coefficient of monolayer graphene composite was studied.The results of tritiated water electrolysis showed that when the electrolysis current was 0.5A and tritiated water was electrolyzed from 20 g to 10g,the H/T separation coefficient of monolayer graphene composite membrane electrode reached 10.45,which was about twice that of graphene free membrane electrode.It indicates that monolayer graphene could improve the H/T separation performance of SPE electrolytic cell.On the other hand,with the extension of electrolysis time or the increase of electrolysis current,the water and H3O+ ion flows destroyed the physical structure of monolayer graphene and made it lose the ability to separate H/T.3)The H/T separation coefficient of graphene nano sheet composite membrane was studied.The results showed that the H/T separation performance of proton exchange membrane could be improved when graphene nanosheets were evenly distributed in the proton exchange membrane.When the specific activity of tritiated water was 3.51 × 104 Bq/L and tritiated water was electrolyzed from 80.00g to 20.00g,the H/T separation coefficient reached 11.32.The H/T separation coefficient of alkaline composite membrane electrode could be significantly improved when graphene nanosheets were mixed with Pt/C catalyst and attached to the cathode of alkaline membrane electrode.When the specific activity of tritiated water was 3.51×104 Bq/L and tritiated water enrichment factor was 4.0,the protium tritium separation coefficient reached 12.55.The above results showed that graphene nanosheets can improve the H/T separation performance of SPE electrolytic cell.In summary,compared with monolayer graphene membrane,graphene nanosheet is more suitable for the efficient treatment of tritiated wastewater.It is with lower cost,simpler preparation process,easier expansion of reaction area and better stability.The results provide a certain theoretical basis and experimental data support for the further study on the graphene efficient treatment of tritiated wastewater. |
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