Preparation of the chitosan/polyacrylonitrile semi-IPN hydrogel via glutaraldehyde vapors for the removal of Rhodamine B dye

In the present study, a chitosan/polyacrylonitrile semi-IPN hydrogel system was developed. To do so various blends of chitosan/polyacrylonitrile were prepared. The miscibility of the polymers, crosslinking of chitosan via glutaraldehyde vapors to produce semi-IPN and microstructures of the hydrogels were determined with DSC, FT-IR and FE-SEM, respectively. The DSC thermograms of hydrogels blends showed a single Tg (at 179–152 °C for Gel1–Gel4), which suggested good miscibility between the two polymers. For semi-IPN (Gel7) the Tg appeared at slightly lower temperature (128 °C), which suggested reduced intermolecular interactions between the two polymers due to the crosslinking of the chitosan. FT-IR showed no change in the characteristic bands positions of the two polymers for hydrogel blends(Gel1–Gel4) and a characteristic doublet at 1563 cm⁻¹ and 1630 cm⁻¹ (for the crosslinking of chitosan with glutaraldehyde) for semi-IPN hydrogel (Gel7). The FE-SEM micrographs showed homogenous (with no phase separation) surface and cross section morphologies for the blends hydrogels (Gel1–Gel4) and semi-IPN hydrogel (Gel7). The aqueous behaviors of the blend hydrogel (Gel1) and semi-IPNs (Gel5–Gel7) were investigated with the reported methods. The % degree of swelling was observed to decrease whereas stability increased as the crosslinking time was increased. The semi-IPN hydrogel (Gel7) showed improved stability and fair swelling. The potential of blend hydrogel (Gel1) and semi-IPNs hydrogel (Gel7) as adsorbents for the adsorption of Rhodamine B dye was studied. Rhodamine B dye showed significant adsorption affinity for semi-IPN hydrogel (Gel7). The data fitted best to pseudo-second-order kinetic and Langmuir isotherm. Intraparticle diffusion model confirmed that diffusion is not the only rate-limiting step, some degree of boundary layer control may be also operating.