Removal of benzene, toluene, ethylbenzene and xylene (BTEX) from aqueous solutions by montmorillonite modified with nonionic surfactant: Equilibrium, kinetic and thermodynamic study

The adsorption characteristics of benzene, toluene, ethylbenzene and xylene (BTEX) from aqueous solutions by montmorillonite (Mt) modified with poly ethylene glycol (PEG-Mt) were investigated. The batch adsorption technique was used to assess the influence of various parameters such as loading rates of the surfactant, contact time, pH, adsorbate concentration, solution ion strength and temperature on the BTEX sorption capacity by PEG-Mt. The raw and modified Mt was specified with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The XRD results showed that the interlayer spacing of the raw montmorillonite (12.10 angstrom) was increased by PEG surfactant modification (17.48 angstrom). The adsorption capacity of the PEG-Mt was increased by increasing the surfactant loading until 200% cation exchange capacity (CEC) of the clay. The equilibrium was achieved at the contact time of 24 h. The adsorption capacity of the adsorbent was in order of B < T < E < X. The experimental data were analyzed by Langmuir, Freundlich and D-R isotherm models. The results indicated that the data were best fitted with the Freundlich isotherm. The D-R isotherm model also showed that the adsorptive behavior of these compounds has physical nature. The obtained data for BTEX adsorption onto the PEG-Mt were also fitted through the pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The correlation coefficients values (R-2) showed that the adsorption kinetic described well by the pseudo-second-order model. The thermodynamic study also indicated that the uptake of BTEX by the adsorbent was spontaneous, endothermic and favorable at higher temperatures. (c) 2012 Elsevier B.V. All rights reserved.