Synthesis and characterization of xylan-gelatin cross-linked reusable hydrogel for the adsorption of methylene blue.

Xylan and gelatin-based hydrogels are prepared in different molar ratios using ethylene glycol diglycidyl ether cross-linker. The hydrogels are characterized by Fourier transform infrared spectroscopy, morphology, thermal analysis, and swelling ratio. The rheological experiment shows the gels are cross-linked successfully by revealing the viscoelastic nature. The xylan-gelatin gel synthesized in a 5:1 molar ratio (hence XG5) has higher storage modulus, gelation temperature, and time among the synthesized gels. The adsorption behaviour of the synthesized gels is studied for the removal of methylene blue, by varying adsorbate concentration, pH, and temperature. Among the synthesized hydrogels, XG5 shows the highest adsorption capacity of 26.04 mg g at pH = 5.84 and 25 °C. The kinetics of the adsorption process follows the pseudo-second-order model, and monolayer adsorption is adequately represented by the Langmuir isotherm model. The adsorption process is established as spontaneous, exothermic, and physisorption from the thermodynamic parameters.