Study On Hyper-acid Tolerance Pervaporation Desaliantion Membranes

Due to the urgent demand for zero discharge of concentration brine solution,pervaporation desalination technology becomes more and more important for brine treatment.Pervaporation has advantages including:energy efficiency,environmental friendliness,and facial operation.Due to the specific characters of industrial wastewaters,suitable membrane materials were required for operational stability.Although there was a large amount of acid wastewater with high concentrated salt content needed to be treated,there was no acid resistant pervaporation membrane being reported.Typical acid-resistant polymers included aromatic polymers,polyether polyesters,sulfone,heterocyclic,polyamides,polysulfonamide etc.Here in this study,we adopted the existed chemical design of acid-resistant polymers,and prepared acid-resistant pervaporation composite membranes.Polysulfonamide was selected as the separation layer material of the composite membranes.Using small molecules,a self-supporting PSA film was prepared in a two-phase solution by interfacial polymerization.By characterizing the PSA before and after soaked in acid,results proved that it had good acid resistance.A polysulfonamide-polyethersulfone(PSA-PES)composite membrane was prepared on the polyethersulfone(PES)support layer.The separation performance for desalinating 35000 ppm sodium chloride(NaCl)solution at 75? was obtained with a water flux of 10.1 kg·m-2·h-1,and a rejection rate of 99.37%.The composite membrane was used to separate water from 10 wt%H2SO4 at 75?.A stable water flux with 100%rejection to H2SO4 was observed,indicating its good acid stability.In order to further improve the membrane water flux,polyethyleneimine(PEI)was used to replace the small molecule in the aqueous system.A new PSA-PES composite membrane was prepared for pervaporation testing.When desalinating 35000 ppm sodium chloride(NaCl)solution,a water flux of 50±1 kg·m-2·h-1 and a salt rejection of 99.93%were obtained.The much higher water flux was resulted from the higher hydrophilicity of the skin layer stemming from the hydrophilic PEI.Through the static acid soaking test of 20 wt%H2SO4 and the high temperature dynamic acid test of 10 wt%H2SO4,the separation performance remained unchanged,which proved that the membrane had good acid resistance.