Preparation And Swift Ion Irradiation Modification Of Graphene Oxide Nanofiltration Membrane

Water is the source of life and an important part of living organisms.At the same time,water resources,as one of the indispensable resources for industrial production and agricultural development,have attracted much attention from all countries.Globally,water scarcity has become a serious problem,especially in some arid or semi-arid regions.The shortage of water resources will have a major impact on the economy,society and the environment,and may lead to problems such as reduced agricultural production,tight food supply,deterioration of the ecological environment,and decline in social stability.Compared with traditional water treatment methods,membrane separation has lower cost and can save energy and water resources.At the same time,membrane separation technology can reduce the use of chemicals,thereby reducing environmental pollution.Therefore,membrane separation technology has become an important means to solve the shortage of water resources,and it is also one of the development directions of water treatment technology in the future.Graphene oxide is a two-dimensional material with an atomic-scale thickness.It is beneficial to the ultrafast transport of water molecules under adjustable layer spacing,and has broad prospects in the field of water treatment.However,in the process of water treatment,the hydrophilic functional groups on graphene oxide will combine with water molecules,causing the interlayer spacing of graphene oxide to increase,resulting in swelling of the membrane,the selectivity of GOM,and the decrease in stability,which seriously limits the performance of GOM.Besides,the separation process of GOM is restricted by the Tradeoff effect,and it is difficult to improve the selectivity and flux of GOM at the same time.In this work,the PET nuclear track membrane was used as the substrate material,and GOM was prepared by pressure-driven filtration and vacuum filtration.Compared with vacuum filtration,pressure-dirven filtration can provide a larger pressure difference,enhance the shear force of liquid flow,and make the arrangement of GO nanosheets smoother and more compact.Therefore,under the condition of the same amount of graphene oxide,pressure-driven filtration can obtain an ultra-thin GO functional layer with more uniform coverage and smoother surface morphology.In this work,GOM was modified by swift heavy ion irradiation in The Heavy Ion Research Facility in Lanzhou(HIRFL),and the effects of different irradiation parameters(irradiation fluence and eletron energy loss)on the morphology structure and nanofiltration performance of GOM were researched.In the GOM after heavy ion irradiation,the number of oxygen-containing functional groups on the membrane surface decreased,and the overall oxygen content decreased,reflecting the reduction of GOM.At the same time,the interlamellar spacing decreases,which enhances the selectivity of GOM after irradiation,increases the rejection rate of different salt ions,and increases the stability of the membrane.The reduction effect of irradiation increases with the fluence and energy loss of heavy ions.At the same time,due to the high energy loss characteristics of the fast heavy ion beam,the high-flux fast heavy ion irradiation will introduce more vertical nanopores on the membrane surface to enhance its flux.Therefore,the modification of GOM by heavy ion irradiation will increase the selectivity and flux at the same time,which provides a new precise and controllable method for the modification of nanofiltration membranes.This work explores more application scenarios of GOM by testing the separation performance of magnesium and lithium of GOM and the separation of heavy metal salts.In the magnesium-lithium separation experiment,the rejection rate of the irradiated GOM to the single salt solution of lithium chloride and magnesium chloride has increased,which is attributed to the reduction of the interlamellar spacing brought about by the reduction of radiation,but at the same time the increased rejection rate It is not conducive to the improvement of the separation ratio of magnesium and lithium separation mixed salts.In the recovery process of heavy metal salts,the selectivity for different heavy metal salt ions is increased due to the decrease of the interlayer spacing of GO nanosheets on the surface of GOM.Therefore,irradiation modified GOM can be applied in the field of heavy metal salt separation and has great potential.Outlook and room for improvement.To sum up,in this work,ultra-thin and flat graphene oxide nanofiltration membranes were prepared by pressure-driven filtration,and GOM was modified by heavy ion irradiation.The modification of GOM by heavy ion irradiation can simultaneously realize the improvement of rejection rate and stability brought by irradiation reduction,and the increase of flux brought by the vertical channels constructed by heavy ion beams,and proposes a new method for the modification of graphene oxide nanofiltration membranes.