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Ion Exchanger using Electrospun Polystyrene Nanofibers Research at The University Of Akron H. An, C. Shin and G. G. Chase ABSTRACT In this study, we have been exploring a new ion exchange material in the form of a nanofiber that could yield a number of important advantages over conventional ion exchange resin. Polymer nanofiber ion exchangers (PNIE) are produced by an electrospinning from solutions of dissolved polystyrene and sulfonation processes. A polystyrene nanofiber cation exchanger was developed for high ion exchange capacity, and rapid ion exchange velocity. In this paper, new experimental results investigating the performance of PNIE are presented in relation to the relevant parameters (ion exchange capacity (IEC), water uptake, and surface property). EXPERIMENTS Elctrospinning Figure 1 shows a schematic diagram of the apparatus used in the electrospinning. The syringe is filled with polymer solution. The polystyrene solution is prepared by dissolving 20 wt% polystyrene in 80 wt% N,N -dimethylacetamide (DMAc). The needle is connected to a power supply and charged to 20,000 volts (Gamma High Voltage Research, Model D-ES30PN/M692). The collecting surface is grounded to attract the charged fibers. A collecting surface is placed at a distance of about 20 cm from the tip of the needle of syringe pump. Sulfonation An electrospun polystyrene nanofiber mat was treated by immersion in 98% sulfuric acid (Aldrich) and Ag 2 SO 4 catalyst with stirring. The electrospun polystyrene nanofiber mat was allowed to occur for 10 to 120 minutes. Finally the sulfonated electrospun polystyrene nanofiber mat were treated to a stepped dilution rinse and followed by rinsing with deionized water. Ion Exchange Capacity (IEC) The IEC of PNIE was measured the following way. Ion exchange capacity, expressed is the measure of the number of replaceable H + ions per unit mass of the exchange. The H + sites on the PNIE were converted into Na + by immersing PNIE in the 30 mL of NaCl solution. where and are the moles of H + in the flask at the initial and the moles of H + and the moles of H + after equilibration. W d is the weight of dried PNIE. Water uptake The water uptake of PNIE is a very important property that to a large degree determines such as conductivity, mechanical strength and permeability. RESULTS Figure 3. SEM images of electrospun fibers of polystyrene (a)untreated PS nanofiber mat (b) 10 minutes sulfonated PS nanofiber mat (c) 30 minutes sulfonated PS nanofiber mat (d) 120 minutes sulfonated PS nanofiber mat. The functionalized (above 30 minutes) PS nanofiber mat having small pore diameters leads to lower capacity because the amount of sulfonating group introduced was restricted by the steric hindrance due to the size of the macroreticular structure under the sulfonation. INTRODUCTION Ion exchange materials (ex. resins and membrane etc.) have been widely used in various industries. The most common applications of ion exchange are water deionization or softening; metal recovery; biological process; food and beverages; pharmaceuticals; and fuel cell. Polymer nanofiber ion exchangers (PNIE) have high surface area, which is larger than two types of resins, membrane and also common fibrous ion-exchangers. Polystyrene nanofiber is unwoven long fiber with diameters in the range of 100-250 nm. PNIE has extremely rapid kinetics, low pressure drop. In our approach, PINE are prepared by polymerization with styrene monomer, electrospinning polystyrene, and sulfonation. Electrospinning process produces nonwoven materials that have high surface and and long polymer fiber with diameters in the range of 10- 500 nm. The electrospinning process is driven by the electrical forces on free charges on the surface or inside a polymeric liquid. When the electric field reaches a critical value at which the repulsive electric force overcomes the surface tension force, a charged jet of the solution is ejected from the tip of a cone protruding from a liquid drop of the polymer. As the jet stretches and elongates in the air, the solvent evaporates, leaving behind a charged polymer fiber that lays itself randomly on a collecting metal screen. Thus, continuous fibers are produced to form a non-woven fabric. Non-woven fibrous materials composed of electrospun fibers have a large surface area and small pore size compared to commercial textiles, making them excellent materials for use in filtration applications. CONCLUSIONS PNIE is produced by an electrospinning from solutions of dissolved polystyrene and sulfonation processes. The PNIE sample for 30 minutes appears highest IEC (4.26 meq/g) and water uptake (7.54 g H 2 O/g-dry- PNIE). The IEC and Water uptake can be related to the sulfonation time and morphology of PNIE. The polymer backbone and sulfonation method are very important to increase IEC. FUTURE WORK Improvements of Thermal, Mechanical and Chemical stability. Test of PNIE of various polymer backbone. PWS Figure 1.Eletrospinning process Figure 2. Sulfonated PS molecular structure. 1 um (a) (d)(c) (b) Figure 4. The relationship between IEC of PNIE and sulfonation time. Figure 5. The relationship between water uptake (g H2O/g-dry-PNIE). of PNIE and sulfonation time.