Preparation Of Sulfonated Electrospun Polystyrene Fibrous Membranes And Its Application

Electrospinning is a very important method to fabricate ultra-fine fibers. Polystyrene is a widely used raw material for ion exchange. Its electrospun fibers may find great potential applications at many aspects of industry and enviromental protection.The objective of this study is to prepare and to estimate the application of sulfonated ultrafine polystyrene (SPS) fibrous membranes (SPSFM) via several steps: firstly preparing PS with designated molecular weight, and then fabricating electrospun PS fibers, and then converting them into sulfonated PS fibrous membranes and finally evaluating the cationic dye adsorption performance of the SPSFM. The additions of sodium dodecyl benzene sulfonate (SDBS), multi-walled carbon nanotubes (MWCNT) into electrospinning dopes and implementation of tubular auxiliary electrode were applied to improve the electrospinning behaviour and electrospun fiber morphology and properties. The solvent steam stewing of electrospun nonwoven mats was used to increase the mechanical strengths of the nonwoven mats. The morphology, structure, properties and cationic dye adsorption of the SPSFM were examined by infrared spectroscopy, scanning electron microscopy, thermogravimetry, universal testing machine and ultraviolet-visible spectrophotometry. The results showed that,(1) The molecular weight and concentration had effects on the electrospinnablity, morphology and properties of PS electrospun fibers. The length of the stable electrospinning jet and the diameter of the resultant fibers were increased with the increase of molecular weight of PS, with the average fiber diameter proportional to the power of 1.831 of viscosity-average molecular weight, the tensile strength at break of ultrafine fibrous membranes increased also with the increase of molecular weight. The suitable solution concentration for electrospinning is 8-15w/v%.(2) The auxiliary tubular electrode postponed the splitting of the electrospinning jets, and thus the area of the electrospun fibrous membrane became much smaller and its density greatly increased, meanwhile, the average diameter of electrospun ultrafine fibers with good morphology slightly increased. The diameter of the auxiliary electrode remarkably affected the jet splitting behaviour. The stronger the electric field was, the more obvious convergence was achieved. The surface tension and electric conductivity of the PS solutions were increased whereas the viscosity was decreased in the presence of SDBS, and thus the splitting process during electrospinning was accelerated with the average diameter of the fibers being gradually reduced. Although the area densities of the electrospun membranes were decreased after addition of the surfactant, the uniformity and the mechanical property of the glossy membranes were remarkably improved, meanwhile, the membranes can be much more easily taken off from the aluminum foil collector.(3) The tensile properties of PS ultrafine fibrous membranes have been greatly improved after heat treatment. The time of immersion in methyl ethyl ketone steam, heating time, temperature and pressure of the process all affect the morphology and mechanical properties. The addition of 1wt% MWCNT to PS obviously improved the tensile strength of PS ultrafine fibrous membrane. The PS fibrous membranes with 1wt% MWCNT after heat treatment showed the biggest tensile strength.(4) With the increase of sulfonation time, the ultrafine fiber surfaces appeared successively many tangential grooves and a lot of outshoots, and the water uptake of the membranes was gained much, and the mechanical properties implied no negative effect due to sulfonation. Cationic dye adsorption of SPSFM demonstrated high adsorption rate and efficient removal. The adsorption with the membranes observed the Lagergren pseudo-second order kinetic process. High efficient removal can be maintained for a long time in the dynamic absorption.The feature and innovations are the following:(1) The effects of the auxiliary tubular electrode and SDBS on the jet splitting behaviour and properties of polystyrene fibrous membranes were studied.The area of polystyrene fibrous membranes was controlled. The uniformity and the detachability of electrospun fibrous membrane from the collector were imporved with SDBS.(2) The heat treatment of electrospun fiber membrane was carried out. The tensile strength of the membrane was improved remarkably.(3) The dynamic adsorption of synthetic cationic dye waste water was conducted with sulfonated polystyrene fibrous membrane, and this would serve as a reference for further investigation in the wastewater treatment.