Lignin - montmorillonite hydrogels as toluene adsorbent

Acrylamide monomer based on lignin/ montmorillonite hydrogels synthesized using N, N’-Methylenebisacrylamide and ammonium persulfate via a cross-linking reaction assisted by ultra-sonication was employed as adsorbent for toluene removal from aqueous solution. The achieved removal percentages are 90.14, 85.09 and 86.81 % for the hydrogels based on alkali, kraft and organosolv lignin’s respectively at 20 min, high concentration of toluene (2 mmol/L), pH 6 and 25 °C. The adsorption efficiency of toluene removal by the hydrogels was strongly enhanced in the case of using alkali lignin. The obtained hydrogels were characterized by Fourier transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Thermal Gravimetric analysis (TGA) and Scanning electron microscopy (SEM). The characterization results showed a good dispersion of MMT and lignin in the hydrogel matrix. In addition, the kinetic data confirmed the pseudo second order and the adsorption isotherms could be better described by the Freundlich equation. Furthermore, the process of adsorption was proved to be feasible and spontaneous thermodynamically. It was also clearly denoted that the prepared hydrogel has an excellent reusability.