Synthesis and Characterization of Methionine-Functionalized Boehmite with Enhanced Removal of Methyl Orange

Abstract

Methionine, an amino acid with thioether, carboxyl, and amino functional groups, was used to enhance the adsorption capacity of boehmite toward methyl orange (MO). An environmentally friendly synthesis method was performed to prepare the methionine-functionalized boehmite (MFB) at 70°C using water as the solvent. The MFB has prominent XRD characteristic peaks at 2θ = 14.5°, 28.6°, 38.4°, and 48.4°. The addition of functional groups from methionine was indicated by the appearance of FTIR bands at 2094, 1424, and 1220 cm-1 corresponding to carboxyl, amino, and thioether groups, respectively. The N2 isotherm curve indicates the mesoporous structure of MFB, with surface area, pore-volume, and mean pore width of 287 m2 g-1, 0.996 cm3 g-1, 13.85 nm, respectively. The kinetic adsorption data showed a good fitting with the pseudo-first-order model, where the equilibrium can be achieved within 50 min. The adsorption of MO by MFB was better correlated with the Langmuir model with a maximum adsorption capacity of 167.4075 mg g-1, which was achieved at 323 K. The thermodynamic study reveals that the adsorption of MO on MFB was an endothermic and spontaneous process.