Research On The Application Of Graphene Oxide-based Membranes In Seawater Desalination

Graphene Oxide(GO)-based membranes have good permeability and excellent selectivity,and have shown great potential in the field of seawater desalination.However,GO based membranes are still facing some problems in the process of application.As filter membranes,the water flux of GO-based membranes is generally increased by preparing ultrathin membranes,but their long-term stability during the high-pressure filtration process is often sacrificed;as an evaporator in the process of interface heating,GO-based membranes still face problems such as reduced absorbance and insufficient water supply caused by surface and bulk salt deposition.Therefore,in order to solve the above problems and promote the practical application of GO-based membranes in the field of seawater desalination,this paper has carried out the following two tasks:(1)The filtration performance of a hierarchically designed reduced graphene oxide(HrGO)membranes with high flux and high stability was studied.The HrGO membrane with hierarchical structure was prepared in one step by hydrothermal method.The ultrathin(20 nm)filter layer and the porous support layer ensure the high flux of the HrGO membranes.At the same time,interlayer ether bonds are formed in the hydrothermal process,which enhances the interlayer force of rGO,which improves the stability of the HrGO membranes in water.Finally,a water flux of 39.8-51.2 L m^-2 h^-1bar^-1 and a cross-flow filtration running time of up to 300 h were achieved under cross-flow condition.HrGO membranes provide a new idea forGO-based membranes to go towards practical application.(2)The salt resistance of reduced graphene oxide(rGO)membranes was studied.We have prepared self-floating rGO membranes as evaporator of interface heating that is resistant to salt deposition.Due to>94%absorbance of the solar spectrum,low interlayer heat conductivity and good water transmission,the rGO membranes have achieved a high evaporation rate of 1.27 kg m^-2 h^-1 in 3.5 wt%salt water under the solar radiation of 1 k W m^-2 and its light-to-heat conversion efficiency is 79%.What is more,the rGO membranes have stable and small interlayer space(3.7(?)),which ensures it a good retention capacity for hydrated salt ions.In the 3.5 wt%and even highly concentrated brine(>5 wt%),the rGO membranes can still maintain stable interface evaporation within 40 h.The rGO membranes have excellent salt deposition resistance,flexibility and stability.The rGO membranes have broad prospects in the field of interface photothermal evaporation and high-concentration brine treatment.