Preparation of Lignin Sulfonate Based/Organo-Montmorillonite Composite Hydrogel for Adsorbing Methylene Blue from Aqueous Solution

In this study, an environmentally friendly lignin-based hybrid hydrogel (LS/OMMT) was prepared by grafting of acrylamide (AM) and acrylic acid (AA) onto calcium lignosulfonate (LS) and homogeneously distributing organic montmorillonite (OMMT) using an ultrasonic technique. FT-IR, XRD, TGA, SEM, EDS, BET, and XPS were used to characterize the physicochemical and structural properties of LS/OMMT. Then, LS/OMMT was applied to remove methylene blue (MB) from an aqueous solution and a systematic study of pH, contact time and initial MB concentration was carried out. The MB adsorption capacity on LS/OMMT was up to 492.7 mg g −1 at 313.15 K and pH 7.0. The Langmuir model well described the MB adsorption on LS/OMMT and the calculated thermodynamic parameters, such as ΔG°, ΔH°, and ΔS°, suggested that MB adsorption on LS/OMMT was spontaneous and endothermic. LS/OMMT adsorption of MB followed a pseudo-second-order kinetic model. Electrostatic attraction and hydrogen-bonding interaction were the mechanisms of adsorption. As a result, this study illustrates that LS/OMMT is an environmentally friendly and efficient adsorbent for wastewater treatment applications.