A pH-sensitive Xylan-based Superabsorbent Hydrogel for the Removal of Methylene Blue from Water

A novel porous xylan-based hydrogel was prepared using methacrylated xylan and acrylic acid via free radical polymerization. The structure, morphology, and thermal stability of the hydrogel were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The pH value had an important effect on the swelling and dye-adsorption properties of the hydrogel. When methylene blue was used as a dye model, the dye adsorption of the hydrogel followed the Langmuir isotherm model and pseudo-second order kinetic model. The calculated maximum adsorption capacity reached 4720 mg/g. Besides, the hydrogel retained about 90% of its adsorptive capacity even after 4 cycles of usage. Therefore, the xylan-based hydrogel presented excellent dye adsorption performance and could be a promising superabsorbent for wastewater treatment.