Highly efficient and fast batch adsorption of orange G dye from polluted water using superb organo-montmorillonite: Experimental study and molecular dynamics investigation

Abstract

Natural montmorillonite (Mt) is modified with cetyltrimethylammonium bromide (CTAB) for obtaining an organoclay. The physicochemical properties of Mt and CTAB-modified Mt (CTAB@Mt) are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, nitrogen sorption, and thermogravimetric/differential thermal analysis. The CTAB@Mt is used as an adsorbent for the removal of orange G anionic dye from aqueous solutions. The adsorption process is examined as a function of adsorbent amount, contact time, temperature, pH, and initial dye concentration. The kinetic study indicates that the adsorption equilibrium of orange G dye onto CTAB@Mt is reached after 30 min and fits well to a pseudo-second-order kinetic model. Also, the adsorption isotherm data is best fitted by a Langmuir model, with the maximum adsorption capacity calculated using the non-linear form of the Langmuir isotherm being 167 mg g−1 at 298 K. The statistical physics model shows that the OG dye could be adsorbed with a non-parallel orientation on the surface of CTAB@Mt. Finally, CTAB@Mt is successfully employed for the treatment of a real wastewater sample from the textile industry. Molecular dynamics simulations are performed to investigate, on one hand, the structural properties of CTAB intercalated into the 2:1 layered Mt and coated on its external surface, and on the other hand, to provide atomic-level insight on the adsorptive characteristics of orange G dye on CTAB@Mt.