Assessment of sulfonation in lignocellulosic derived material for adsorption of methylene blue

Abstract

The lignocellulosic derived cornstalk was sulfonated (SCS) to prepare an adsorbent, and cationic dye methylene blue (MB) was adsorbed using SCS to evaluate its usability. Sulfonation improved the number of carboxyl groups (-COOH) and increased the porosity and surface area of carbon. In the adsorption process in which MB is adsorbed using SCS in aqueous solution, the sulfone group expanded the form of the sulfonated adsorbent to increase the exposure of anions (sulfonic-acid (R-SO3H), carboxylic groups, and bonded OH-group) to the surface. As a result, the adsorption efficiency of MB, a cationic dye for SCS, was improved. The results of kinetics, adsorption isotherm and thermodynamics were suitable for Pseudo-2nd-order and Langmuir, and the adsorption process was endothermic and spontaneous physical adsorption. The maximal adsorptions capacity with Langmuir model was found to be 504.3 mg/g at 293K. Sulfonation improved not only electrostatic interaction but also π-π stacking in the adsorption process, which was very advantageous in adsorbing cationic dyes using lignocellulose-based adsorbents.