Anionic surfactant-modified rice straw for removal of methylene blue from aqueous solution

This research reports on the development of organo-modified rice straw (RS) adsorbent prepared using sodium dodecyl sulfate (SDS) for removing methylene blue (MB), a model cationic dye, from aqueous solution. The natural and modified samples were characterized by scanning electron microscopy, nitrogen physisorption, and Fourier transform infrared spectroscopy. Batch adsorption experiments were carried out to remove MB from its aqueous solutions using SDS-modified RS (SMRS). The different parameters affecting the adsorption capacity such as pH of the solution, initial dye concentration, and contact time have been investigated. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on the SMRS can be described perfectly with the Langmuir isotherm model compared with the Freundlich isotherm model, and the characteristic parameters for each adsorption isotherm were also determined, and the Langmuir adsorption capacity, Q(max), was found to be 296mg/g for SMRS and 145mg/g for RS at 303K, respectively. The adsorption kinetic followed the pseudo-second-order kinetic model. Desorption studies suggest that MB adsorption onto the SMRS should be mainly controlled by the hydrophobic interaction mechanism, along with a considerable contribution of the cationic exchange mechanism.