Experimental and molecular dynamics simulation study on the adsorption of Rhodamine B dye on magnetic montmorillonite composite γ-Fe2O3@Mt

Abstract In the present work, we synthesized successfully novel magnetic montmorillonite composite γ-Fe2O3@Mt by a facile co-precipitation method of Fe2+ and Fe3+ in alkaline solution in the presence of montmorillonite clay mineral. The structural, morphological and chemical properties of the γ-Fe2O3@Mt samples were characterized by Fourier transform infrared spectroscopy, Thermogravimetric Analysis/differential thermal analysis, Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, Energy Dispersive X-Ray Spectroscopy/Elemental Mapping, Transmission electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller surface area, zeta potential and magnetic properties. The adsorption process of Rhodamine B (cationic dye) onto γ-Fe2O3@Mt was examined as a function of adsorbent amount, pH, contact time and initial dye concentration. The maximum quantity adsorbed of RhB dye onto Fe2O3@Mt was found as 209.20 mg/g. The kinetic study indicated that the adsorption equilibrium of Rhodamine B dye onto γ-Fe2O3@Mt was obtained after 25 min. The adsorption isotherms were described by Langmuir isotherm model suggesting that the Rhodamine B dye molecules are adsorbed homogeneously on a monolayer surface of γ-Fe2O3@Mt. The experimental data were well fitted to a pseudo-second-order kinetic model (R2 > 0.99). A Computational modeling was performed in order to obtain deeper mechanistic insights on the adsorption behaviour of the RhB dye molecules onto γ-Fe2O3@Mt.composite. This modeling section include Monte Carlo space exploration for the lowest adsorption energy configurations of the RhB molecule on the raw Mt. substrate and the different γ-Fe2O3 flat nanosurfaces, followed by molecular dynamics simulation of the titled dye molecules on real cylindrical maghemite nanosurface.