The characterization of organo-montmorillonite modified with a novel aromatic-containing gemini surfactant and its comparative adsorption for 2-naphthol and phenol

Abstract

A novel aromatic-containing gemini surfactant, bis-N,N,N,-hexadecyldimethyl-p-phenylenediammonium dibromide (BHPD) was used to modify Na-montmorillonite for the first time. The surface and structure of the resultant organoclays were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), elemental analysis (EA) and Zeta potential. The results showed that interlayer space of the Na-montmorillonite was significantly expanded at relatively low concentration of BHPD. The comparative study for the adsorption of 2-naphthol and phenol from aqueous solution was performed on the resultant organo-montmorillonites. The results suggested that the adsorption amount of 2-naphthnol was much higher than that of phenol under the same condition, which may be attributed to the stronger hydrophobicity of 2-naphthol and its higher delocalized π-electron density. The important factors, such as the amount of modifier, contact time, temperature and pH in the solution, were also taken into consideration. Additionally, the kinetics and thermodynamics parameters were investigated, it was found that the reaction process was completed in a short time, the experimental data fitted very well with the pseudo-second-order kinetic model, and the equilibrium adsorption data were proved to be in good agreement with the Freundlich isotherm model. Thermodynamic parameters Gibbs free energy (ΔG°), the enthalpy (ΔH°) and the entropy change of sorption (ΔS°) demonstrated that the adsorption of 2-naphthol and phenol was a spontaneous and exothermic process.