MgAl-LDH/Biochar composites for methylene blue removal by adsorption

Abstract

AbstractIn this work, LDH-biochar composites were synthesized in different molar ratios of Mg:Al (2:1, 3:1 and 4:1) using co-precipitation method. The composites were applied to remove an organic dye from aqueous solutions by adsorption. The composites and the pure bovine bone biochars were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) measurements, thermogravimetric analysis (TG/DTG), dispersive energy spectroscopy (DES) and scanning electron microscopy (SEM). The methylene blue dye adsorption experiments were conducted in a finite bath. The results indicate that pH 12 is more suitable for dye adsorption process, with a removal >95% for all composites. The adsorption kinetic was best described by the pseudo-second order model, reaching the equilibrium in approximately 20 min. The Redlich-Peterson model fit the adsorption equilibrium isotherms satisfactorily. It was obtained a maximum adsorption capacity of 406.47 mg·g−1 at 40 °C. Negative values of ΔG indicate the spontaneity of the adsorption process. The positive value of ΔH (30.72 kJ·mol−1) indicates the physical nature of the adsorption and the positive value of ΔS (0.1863 kJ·mol−1) indicates that there was a change in the structure of the adsorbent and increased randomness during the fixing of the dye.