Ion Exchange Functional Nanofibers
- PDF / 430,169 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 60 Downloads / 199 Views
1240-WW10-03
Ion Exchange Functional Nanofibers Prabir K. Patra1 and Sukalyan Sengupta2 1 Mechanical Engineering Department, University of Bridgeport, Bridgeport, CT 06604, U.S.A. 2 Civil and Environmental Engineering Department, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, U.S.A. ABSTRACT We have synthesized a series of functionalized ion exchange fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, PS was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100 micron) were then produced from the functionalized PS using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 - 270 °C. Fiber was drawn at 120 °C with a draw ratio of 2. Electrospinning of functionalized PS was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun PS and polyisoprene (PIP) blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers PAN was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show CEC of 3.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and PIP was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium. INTRODUCTION Ion Exchange is a mature and broad field with application in catalysis, drug delivery, sensors, bioseparation, membranes, ore beneficiation, metallurgy, food purification, polymer synthesis, inorganic materials, biorenewable energy, water treatment, environmental processes, nanotechnology and several others. However, the morphology of the ion exchanger is still limited to spherical beads or membranes. Ion exchange beads and membranes suffer from limitations such as their (a) inability to be used in reactors with high suspended solids/slurries, (b) slow exhaustion and regeneration kinetics, and (c) minimum size/thickness possible. Ion exchange fibers – which can be viewed as slender strands of a polymer with covalently attached functional groups on the surface - can overcome these limitations. The main benefits of the ion exchange fiber are (i) higher surface area and consequently higher density of functional groups per unit mass, (ii)
Data Loading...
