Functional Preparation Of Polysulfone Membrane And Its Application In Seawater Desalination Process

Compared with the traditional seawater desalination technology,the membrane process is expected to become the most economical seawater and brackish water desalination technology because of its high desalination efficiency,low energy loss,small footprint and low pollution to the environment.As new desalination technologies,membrane distillation and photothermal conversion membrane have increasingly wide application prospects in seawater desalination,wastewater treatment and other fields.However,with the further expansion of the application field of separation membrane,higher requirements are put forward for its separation efficiency and anti-fouling.In the process of membrane distillation,the treated solution is not only a single salt solution,but also complex systems containing organic solvents,surfactants,enzymes or proteins.At this time,a single superhydrophobic membrane don't solve the membrane surface wetting and fouling problems caused by the complex liquid system.In order to solve this problem,we successfully prepared amphiphobic PSf membrane.Through the traditional non-solvent induced phase conversion method and further sol-gel process,the double re-entrant structure was successfully constructed.Specifically,the interpenetrating network pore structure obtained by optimizing the phase separation parameters provided the first re-entrant structure;the spherical and different sizes of Si O2 nanoparticles generated by the sol-gel method on the membrane surface provided the second re-entrant structure.After further modification of fluorine-containing chemicals,the PSf membrane with double re-entrant structure showed excellent and stable wetting resistance to water and organic liquids.Even the organic droplets of hexadecane and n-hexane with extremely low surface tension have higher contact angles on the prepared membranes surface,which was 121 °and 67 °,respectively.Compared with the hydrophobic membrane,the amphiphobic PSf membrane achieved long-term stable steam flux and salt interception rate in the process of membrane distillation.Different from the membrane distillation technology,which is driven by thermal energy,the photothermal conversion membrane technology uses solar energy for seawater desalination,having the advantages of cleaner,green,pollution-free,coordinated and sustainable.It is widely regarded as a promising seawater desalination and water purification technology.The development of new photothermal conversion membranes and the improvement of photothermal conversion efficiency have become the focus of current research.Here,we constructed a new preparation strategy of composite membrane,which was composed of hydrophobic PSf membrane and hydrophilic r GO/PS layer.The hydrophobic PSf membrane effectively restrained the diffusion of heat from the membrane surface to the water body and ensured that the heat energy was limited to the evaporation surface because of the low thermal conductivity of the cell-like structure obtained by the solvent volatilization process.The r GO/PS layer deposited on the hydrophobic PSf membrane showed high broadband solar absorptivity and enhanced photothermal conversion ability in the range of 250-2500 nm,which was mainly due to the designed cell-like structure.The prepared r GO/PS@PSf composite membrane combined the characteristics of thermal insulation,solar energy absorption and water supply,and avoided the complexity of preparation and application.Finally,r GO/PS@PSf composite membrane showed excellent solar water evaporation efficiency of 63.83% in one sunlight.In addition,with the addition of CB,the photothermal conversion efficiency had been further improved,up to 66.9%.This composite structure maked it a promising material for efficient seawater desalination.