Polyamidoxime/Poly(vinyl alcohol) Composite Chelating Fiber Prepared by Emulsion Spinning and Its Adsorption Properties for Metal Ions

Abstract

The precursor polyacrylonitrile/poly(vinyl alcohol) (PAN/PVA) fibers were prepared by emulsion spinning of PAN emulsion with PVA solution. The precursor fibers were then amidoximated to get the polyamidoxime (PAO)/PVA composite chelating fibers. The structures of PAN emulsion particles and composite fiber were studied with a laser mastersizer, scan electronic microscope, Fourier transform infrared spectra, auto-Kjeldahl determination, and X-ray diffraction analysis. Results show that nanosized PAN particles were well-dispersed in PVA fiber matrix through emulsion spinning. Almost all of the PAN particles were amidoximated after treatment. The PAO/PVA fiber has good selectivity to silver ions in a multiple metal ions solution. Its maximum amount of adsorption of silver ions and copper ions were calculated to be 518 and 146 mg g −1 according to the Langmuir model. It also has good mechanical performance with breaking strength, 392.10 MPa, and elongation at break, 30.19%.

Water‐resistant modification of poly(vinyl alcohol)/polyamidoxime chelating fibers prepared by emulsion spinning and their adsorption properties

“…Figure shows the FTIR spectra of composite fibers on different modification stages. The peak of the precursor PVA/PAN fiber at 3407 cm −1 was attributed to the vibrations of OH of PVA and the peaks at 2244 and 1730 cm −1 were due to the CN and COOCH 3 of PAN copolymer . After the crosslinking modification, the intensity of hydroxyl peak decreased and shifted to 3414 cm −1 (curve b), 3425 cm −1 (curve c), and 3418 cm −1 (curve d).…”

“…XRD patterns of composite chelating fibers are showed in Figure . The diffraction peaks at 11.13°, 19.17°, and 22.19° [Figure (a–d)] were attributed to (100), (101), and (200) crystallographic planes of PVA, and the peak at 16.8° of PAN was not observable due to the successful preparation of amidoximated composite fibers . The uncrosslinked PVA/PAO fiber showed stronger peak intensity than those of crosslinked composite chelating fibers, indicating that the crosslinking treatment would do harm to the structure of PVA/PAN precursor fibers.…”

“…PAN was prepared by emulsion copolymerization (acrylonitrile (AN): acrylic acid (AA): methyl methacrylate (MMA) = 45 g: 2.25 g: 1.6 g). PVA/PAN precursor fibers were prepared by emulsion spinning according to the reference . The as‐spun precursor fiber was hot stretched five times (which is the highest ratio that the fiber can be stretched) to get the best mechanical strength and the highest specific surface area.…”

“…As the well‐known formalization modification for PVA fiber, sealing or crosslinking the free hydroxyl groups of PVA are the effective ways to elevate the water resistance of PVA fiber . However, the free hydroxyl groups of PVA were thought to participate the adsorption process of PVA/PAO composite chelating fibers, so they are not expected to be largely sealed or crosslinked in the formalization process. The traditional formalization uses extremely permeable formaldehyde (FA) as the crosslinker, which would almost completely seal the free hydroxyls of PVA and largely lower down the hydrophilicity of the fiber matrix.…”

“…The structures of most precursor fibers would be destroyed during the amidoxime modification processes, which largely deteriorate the mechanical strength of the obtained amidoxime chelating fibers . To solve this problem, we prepared a poly(vinyl alcohol)/polyamidoxime (PVA/PAO) composite chelating fiber by emulsion spinning . In this composite fiber, the absorptive PAO particles are supported by coriaceous PVA fiber matrix which is not influenced by the amidoxime modification process.…”