Hydrogel Beads of Amidoximated Starch and Chitosan as Efficient Sorbents for Inorganic and Organic Compounds

Abstract

The synthesis of hydrogel beads involving natural polymers is, nowadays, a leading research area. Among natural polymers, starch and chitosan represent two biomolecules with proof of efficiency and low economic impact in various utilization fields. Therefore, herein, the features of hydrogel beads obtained from chitosan and three sorts of starch (potato, wheat and rise starches), grafted with acrylonitrile and then amidoximated, were deeply investigated for their use as sorbents for heavy metal ions and dyes. The hydrogel beads were prepared by ionotropic gelation/covalent cross-linking of chitosan and functionalized starches. The chemical structure of the hydrogel beads was analyzed by FT-IR spectroscopy; their morphology was revealed by optical and scanning electron microscopies, while the influence of the starch functionalization strategies on the crystallinity changes was evaluated by X-ray diffraction. Molecular dynamics simulations were used to reveal the influence of the grafting reactions and grafted structure on the starch conformation in solution and their interactions with chitosan. The sorption capacity of the hydrogel beads was tested in batch experiments, as a function of the beads’ features (synthesis protocol, starch sort) and simulated polluted water, which included heavy metal ions (Cu2+, Co2+, Ni2+ and Zn2+) and small organic molecules (Direct Blue 15 and Congo red).

Polysaccharide-Based Composite Hydrogels as Sustainable Materials for Removal of Pollutants from Wastewater

“…In our group, composite biosorbents were prepared as beads, using CS and polyacrylonitrile (PAN)- g -St [ 106 ] or poly(amidoxime) (PAMOX)- g -St [ 23 , 126 ] by dual cross-linking methodologies for HMI removal from simulated wastewater. For example, CS/PAN- g -St beads obtained by dual chemical cross-linking using GA and poly(ethylene glycol diglycidyl ether) through a fast cryostructuration methodology (dropping the precursor mixture composed of grafted St powder, CS solution, and cross-linkers into liquid nitrogen) were investigated as sorbents for Cu(II), Ni(II), and Co(II) ions [ 126 ]. Among different St sources (potato, wheat, and rice, abbreviated with GPS.3, GWS, and GRS, respectively, in Figure 8 A,B), the composites prepared using rice St gave the highest HMI sorption performance ( Figure 8 A), probably due to a more favorable amylose to amilopectin ratio [ 127 ].…”

Versatile Zwitterionic Beads for Heavy Metal Ion Removal from Aqueous Media and Soils by Sorption and Catalysis Processes

“…For cleaning water, both synthetic and natural polymers are attractive. They can be employed as membrane coatings, flocculants, or for the low-cost production of various sorbents for pollutants like fibers, hydrogels, resins, or core–shell particles. – The synthetic ionic exchange resins are synthetic polymers that takes advantage of the properties of forming chelates with HMIs and exchanges them with nonharmful hydrogen ions. ,,– They are reusable and highly stable in alkaline or acidic solutions. Column laboratory studies, which are considered preliminary to implementing a larger scale solution, are recommended for improving HMI sorption efficiency under real application conditions.…”

Gels: Synthesis, Characterization and Applications in High Performance Chemistry

“…Molecular dynamics simulations were used to reveal the influence of the grafting reactions and grafted structure on the starch conformation in solution and their interactions with chitosan. The sorption capacity of the hydrogel beads was tested in batch experiments, as a function of the beads’ features (synthesis protocol, starch sort) and simulated polluted water, which included heavy metal ions (Cu 2+ , Co 2+ , Ni 2+ and Zn 2+ ) and small organic molecules (Direct Blue 15 and Congo red) [ 12 ].…”