Methyl Orange Adsorption by Modified Montmorillonite Nanomaterials: Characterization, Kinetic, Isotherms and Thermodynamic Studies

Clays intercalated with cetyltrimethylammonium bromide (CTAB-Mt) and hydroxyl aluminium polycation have been prepared and analysed by X-ray fluorescence spectrometry, X-ray diffraction, fourier transform infrared spectroscopy, nitrogen adsorption-desorption at 77 K and thermal gravimetric analysis. The adsorption capacities of modified montmorillonite nanomaterials to remove methyl orange (MO) from aqueous solutions have been studied as a function of contact time, solution pH, adsorbent dosage and initial MO concentration at room temperature. The maximum removal efficiency of MO has been found in acidic medium, with 60 min equilibrium time and 1 g/L adsorbent dosage. The adsorption kinetics and isotherms have been well fitted by pseudo-second order and Langmuir models. The montmorillonites intercalated with both cetyltrimethylammonium bromide and hydroxyl aluminium polycation (CTAB-Al-Mt) have shown a high affinity for MO molecules. Thermodynamic results have indicated an exothermic, spontaneous and physical adsorption process. The characterization and adsorption performance of CTAB-Mt and CTAB-Al-Mt toward MO has also been compared with that of the hydroxyl-aluminium pillared montmorillonite (OH-Al-Mt) and purified montmorillonite (Na-Mt).