Modification Of Electrospun Polysulfone Fibrous Membrane And Its Filtration Property To Dyes

Membrane filtration is a clean producing technique, which has excellent separationefficiency, mild operating conditions and simple equipments, so that it is widely used inindustry waste water and special waste water treatment. It can be realized that the dyes arerecycled in dying waste water through membrane filtration. Although there are manymethods to prepare filtration membranes, the electrospun fibrous membrane is paidextensive attention for their high specific surface area, throughout pores and high porosity.Polysulfone (PSF) is widely used as waste water filtration membrane material for itsexcellent chemical and thermal stability. The diameter of PSF fibers can reach fromhundreds to thousands nanometer through electrospinning technique, and the pore size ofelectrospun PSF membrane can reach thousands nanometer. Meanwhile PA6/66also hasgood chemical stability, and its electrospun fiber diameter can reach dozens of nanometer,its membrane pore size is to a few nanometers. So these two electrospun membranes havepotential application in dye waste water. But till now, there was not systematic research ofthese two membranes used in filtering dye waste water.In this paper，the parameters of electrospun polysulfone fibrous membrane wereoptimized. In order to improve the strength of the membrane which was obtained atoptimized parameters, dry heat treatment parameters were also optimized. The resultsshowed that when polysulfone was dissolved in DMF under room temperature, theconcentration of spinning solution was20wt%, spinning voltage was12kV，collectingspinning distance was15cm，solution flow rate was1.5ml/h, the obtained fibers had bettermicro-morphology. When the optimized membrane was treated at190℃for2h withloading tension, the membrane has better mechanical property, which can be regarded asthe optimized heat treating parameters. The average pore size of membrane was4.5μm andits surface contact angle was130.2°under this condition.The pH value of dye waste water is from2to14, and the membranes may be cleaned by chemical solvent at some time. In this paper, the stability of electrospun PSF membraneand PA6/66membrane in different pH value of hydrochloride and sodium hydroxidesolution, deionized water,1%H2O2and0.5%NaClO were studied, and the wet thermalstability in hot deionized water was also studied. The results showed that190℃-2helectrospun PSF membrane had excellent stability in above solution, and also had excellentthermal stability in deionized water below60℃, but the morphology and porous structureof membrane was damaged seriously after treated in deionized water at80℃for4+4days.So it can be cleaned by the above solution and can be used under60℃for long time. Theelectrospun PA6/66membrane which was treated at90℃for15min under wet condition,had good stability in different pH value of hydrochloride and sodium hydroxide solution,but was damaged seriously in1%H2O2and0.5%NaClO solution, So it can not be cleanedby H2O2and NaClO solution. It has good stability in hot deionized water below40℃, butwas damaged seriously under60℃.In order to improve the hydrophilicity and mechanical property of electrospun PSFmembrane, and also decreased its pore size, so that it can remove dyes, decrease membranefouling and resist larger filtering pressure. The190℃-2h electrospun PSF membrane wastreated by O2plasma at first, then it was padded by chitosan solution crossliked withglutaraldehyde. The results showed that the hydrophilicity and mechanical property of themembrane were both improved significantly, and its pore size was also decreased largely.After the membrane was padded with2%-120crosslinked chitosan solution which meansmass percentage of chitosan was2%and volume of glutaraldehyde was120μl, its poresize was below0.09μm due to partial pores were covered by chitosan, its initial modulusand breaking strength increased by277.2%and126.8%respectively, and its breakingenlongation decreased by86.9%. After the membrane was padded with2%-100crosslinked chitosan solution, its average pore size decreased from4.5μm to2.62μm, itsinitial modulus and breaking strength increased by134.7%and53.9%respectively，and itsbreaking enlongation decreased by77.2%。The filtration property of190℃-2h electrospun PSF membrane,2%-100modified PSFmembrane,2%-120modified PSF membrane and90℃-15min electrospun PA6/66membrane to disperse blue2BLN suspension and weak acid blue N-RL solution wasstudied under dead-end condition. The results showed that the separation factor of2%-120 modified PSF membrane was99.5%, when the concentration of disperse blue2BLNsuspension was0.1g/L under constant pressure0.1MPa, but the filtration flux was greatlysmaller than other membranes. The separate factors of other membranes were similar, allabove94%, and the filtration flux was going to same after filtering for25min. Theseparation factor of2%-120modified PSF membrane was not changed obviously when thefiltration pressure was increased from0.1MPa to0.3MPa. Meanwhile multi-layers couldnot increase the separation factor, and there was not obvious relationship betweenconcentration of disperse blue and separation factor of electrospun PSF membrane. Whenfiltered0.1g/L weak acid blue solution under constant pressure0.1MPa, the separationfactors of190℃-2h electrospun PSF membrane and90℃-15min electrospun PA6/66membrane were all smaller, but the stable filtration flux were similar, which was at45～51L/m2.h. The separation factor of2%-120modified PSF membrane was above92.4%,and the permeated solution was clearer, but the filtration flux was still too small, which isthe main defect of the modified membrane.