Synthesis of a novel functional group-bridged magnetized bentonite adsorbent: Characterization, kinetics, isotherm, thermodynamics and regeneration

A novel magnetic adsorbent was synthesized by magnetizing bentonite by APTES-Fe3O4via a functional group-bridged interaction. The characterization of APTES-Fe3O4/bentonite was conducted via transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FT-IR), thermal gravimetric analysis (TGA), vibrating sample magnetometer (VSM), zeta potential analysis and Brunner-Emmet-Teller (BET). The APTES-Fe3O4/bentonite was assessed as adsorbents for methylene blue (MB) with a high adsorption capacity (91.83 mg·g− 1). Factors affecting the adsorption of MB (such as pH, equilibrium time, temperature and initial concentration) were investigated. The adsorption process completely reaches equilibrium after 120 min and the maximum sorption is achieved at pH 8.0. The adsorption trend follows the pseudo-second order kinetics model. The adsorption data gives good fits with Langmuir isotherm model. The parameter factor RL falls between 0 and 1, indicating the adsorption of MB is favorable. The adsorption process is endothermic with positive ΔH0 values. The positive values of ΔG0 confirm the affinity of the adsorbent towards MB, and suggest an increased randomness at the solid-liquid interface during the adsorption process. Regeneration of the saturated adsorbent was easily carried out via gamma-irradiation.