Xanthan Gum and Lignin Grafted Chemically Crosslinked Hydrogels for Dye Removal: Synthesis, Characterization and Isotherms Studies

In the present investigation synthesis of Xanthan Gum (XG-g-PAAcoAM), Lignosulphonate sodium salt (LS-g-PAAcoAM), and their combination (XG/LS-g-PAAcoAM) based hydrogels by grafting them onto acrylic acid and acrylamide for efficient removal of Methylene Blue dye have been reported. The results were found to be reliable with a removal rate exceeding 91% when administered at a dosage of 0.2 g in a 20 mL solution of Methylene blue dye over a period of 7 h. The hydrogels have been characterized by various techniques using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction analysis. Among the three commonly used isotherms (Langmuir, Freundlich, and Temkin), the Freundlich isotherm model exhibits the highest level of fit for the dye adsorption as evident with the R² value of 0.99. This study provides a meaningful comparative insight towards using these natural polymers i.e., XG and LS as feedstock for hydrogel synthesis and efficient adsorbent for wastewater treatment applications.