Cyclodextrin (CD)-based polymers are known to efficiently form molecular inclusion complexes with various organic and inorganic guest compounds. In addition, they also have a great potential as metal complexes because deprotonated hydroxyls can strongly bind metal ions under alkaline conditions. The range of environmental conditions for polycyclodextrin/metal ion complexation can be extended by the polymerization of CDs with polyacids. This article describes the preparation and characterization of a new type of poly(β-cyclodextrin) (Poly-βCD) sub-micrometric fibers and explores their potential as metal ion sorbents. A water-soluble hyper-branched β-cyclodextrin polymer was blended with poly(vinyl alcohol) (PVA) and here used to improve the mechanical and morphological features of the fibers. Solutions with a different Poly-βCD/PVA ratio were electrospun, and the fibers were cross-linked by a post-spinning thermal treatment at 160 °C to ensure non-solubility in water. The fiber morphology was analyzed by scanning electron microscopy (SEM) before and after the curing process, and physical-chemical properties were studied by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The capability of the insoluble cyclodextrin-based fibers to remove heavy metals from wastewaters was investigated by testing the adsorption of Cu2+ and Cd2+ using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The results suggest that the poly(β-cyclodextrin)/poly(vinyl alcohol) sub-micrometric fibers can complex metal ions and are especially effective Cu2+ sorbents, thus opening new perspectives to the development of fibers and membranes capable of removing both metal ions and organic pollutants.
Keywords: electrospinning; fibers; heavy metals; polycyclodextrin; polysaccharides; sorbent materials; wastewater.