Fast microwave-assisted green synthesis of xanthan gum grafted acrylic acid for enhanced methylene blue dye removal from aqueous solution

In the present project, graft polymerization was employed to synthesis a novel adsorbent using acrylic acid (AA) and xanthan gum (XG) for cationic methylene dye (MB⁺) removal from aqueous solution. The XG was rapidly grafted with acrylic acid (CH₂ = CHCOOH) under microwave heating. Fourier-transform infrared spectroscopy (FTIR), Proton Nuclear magnetic resonance spectroscopy (¹H NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Thermal gravimetric analysis (TGA) techniques were used to verify the adsorbent formed under optimized reaction conditions. Optimum reaction conditions [AA (0.4 M), APS (0.05 M), XG (2 g L⁻¹), MW power (100%), MW time (80s)] offer maximum %G and %GE of 484 and 78.3, respectively. The removal ratio of adsorbent to MB⁺ reached to 92.8% at 100 mg L⁻¹. Equilibrium and kinetic adsorptions of dyes were better explained by the Langmuir isotherm and pseudo second-order kinetic model respectively. The results demonstrate xanthan gum grafted polyacrylic acid (mw XG-g-PAA) absorbent had the universality for removal of dyes through the chemical adsorption mechanism.