Selective capture and separation of cationic/anionic guest dyes using crosslinked soy polysaccharide-based hydrogel nanostructure

Abstract The distinctive selective adsorption of the hydrophilic dyes gives the hydrogel nanostructure (HGNS) potential in the separation. Herein, we introduced the beta-cyclodextrin (β-CD) to enhance the rheological properties, mechanical strength, thermal stability, and sorption of the soy soluble polysaccharides (SSPS). We have studied the detailed structures and morphology by FTIR, XRD, XPS, TGA, SEM, TEM, and AFM. Inspired by its unique selective sorption and high stability, our HGNS may be able to remove and separate dye mixtures in aqueous solutions simultaneously. To evaluate the (SSPS/β-CD-HGNS) as an adsorbent, we used two fluorescein dyes Eosin water-soluble (EWS) and Fluorescein sodium (FRS), besides different five chemical dyes (Trypan blue (TB), Crystal violet (CV), Methyl orange (MO), Toluidine blue (ToB), and Congo red (CR)) separately and in mixture. The adsorption process followed pseudo-second-order kinetics and intra-particles diffusion. Based on the equilibrium adsorption data, it was found that the Langmuir model was suitable for describing the adsorption equilibrium by the HGNS network of TB, CV, and ToB. In contrast, the Freundlich model was appropriate for MO, CR, EWS, and FRS. The maximum adsorption amount for TB, CV, MO, ToB, CR, EWS, and FRS reached to (37.51, 91.42, 48.00, 64.79, 60.53, 2.30, 1.86 μmolg-1), respectively.