Enhanced Water Absorption and Tunable Swelling Behavior in Chemically Crosslinked Isinglass/Agar Hydrogel Beads

ABSTRACT Isinglass/agar hydrogel beads were synthesized using a self‐assembly method at a water‐in‐oil emulsion interface. The hydrogel was chemically crosslinked using glutaraldehyde to generate stable aldimine bonds with amino (–NH 2 ) groups present in isinglass. Fourier‐transform infrared spectroscopy (FTIR) was utilized to determine the generation of chemical crosslinks within the hydrogel. The hydrogel's porous and interconnected three‐dimensional morphology was investigated with field emission scanning electron microscopy (FE‐SEM). The resulting hydrogel beads demonstrated a narrow and uniform size distribution ranging from 3.5 to 3.75 mm, confirming the reproducibility of the synthesis method. The equilibrium swelling ratio was reduced as the crosslinking agent concentration increased, resulting in water uptake decreasing from about 1358% to 753%. Also, the swelling ratio was very sensitive to pH changes, showing a maximum (~1580%) at pH 3 and decreasing as pH increased. The swelling ratio increased with the temperature, reaching approximately 1960% at 60°C. Analysis of the swelling kinetics showed that the swelling behavior was in good agreement with the pseudo‐second‐order model, implying the presence of chemical interactions between the polymeric chains and the molecules of water. These findings suggest that these hydrogels could be suitable for wastewater treatment, contaminant removal, or controlled release.