The Mechanism Study On The Effect Of Additives On The Structure Of Reverse Osmosis Support Membrane

Polysulfone(PSF)ultrafiltration membranes were prepared fromseries of casting solutions with different compositions by immerse phaseinversion process at the condition of the constant ambient temperatureand ambient relative humidity. N, N-dimethlacetamide (DMAc) was usedas casting solvent. Non-solvent water and surfactants(Sodium DodecylSulfonate, Polyethylene Glycol Mono-4-nonylphenyl Ether Phosphate,TritonX100,TritonX114)wereusedasadditives.Purewaterwasusedascoagulation bath. Different molecular weight of polysulfone affected oncasting solutions viscosity, membrane performance and structure wereinvestigated. One of this work was to investigate the influence of severaladditives and their content on the casting solutions viscosity, membraneperfoemance and structure. Further more, the membrane formationmechanism was discussed. The effect of casting solutions temperature,solvent evaporation time and solvent composition on membraneperformanceandstructurewerealsoresearchedhere.Based on experimental results, for Polysulfone had larger molecular weight, the casting solutions viscosity was larger, the amount andaperture of pore on surface decreased, the flux of pure water reduced, therejection increased. With the increase of non-solvent additive water, thecastingsolutionsviscosityincreased,thefluxofpurewaterincreased,therejectiondeclined.When surfactants were used as additive and the content increased,the casting solutions viscosityfirstlyrised and then decreased, the flux ofpurewateralsoshowedthesamerule,therejectiondeclined.With the increase of casting solution temperature, the castingsolutions viscosity reduced, the flux of pure water firstly increased andthen decreased, while rejection is opposite. Whether surfactants wereattended or not, the flux of pure water firstlydecreased then increased byincreasing solvent evaporation time, while the rejection firstly increasedand then decreased. When the solvent evapoeation time increased, theamount ofsponge-like poreonthecross-sectionstructure membrane withsurfactants as additive in casting solution increased, the finger-like porenearlydisappeared.WhileN,N-dimethlacetamide(DMAc)andDimethylcarbonate(DMC)were used as solvent, the flux of pure water firstlyincreasedthendescended,therejectiondescended.