Comparison between Asymmetric and Symmetric Gemini Surfactant-Modified Novel Organo-vermiculites for Removal of Phenols

To study the effect of the asymmetry of gemini surfactants on the adsorption characteristics of organo-vermiculites (OVts), [C14H29(CH3)(2)N+(CH2)(6)N+-(CH3)(2)C14H29]Br-2 (termed 14-6-14) and [C22H45(CH3)(2)N+-(CH2)(6)N+(CH3)(2)C6H3]Br-2 (termed 22-6-6) with the same number of carbon atoms were designed to modify vermiculite for removing p-chlorophenol (PCP), phenol (P), and p-methylphenol (PMP) from aqueous solution. The resulting OVts were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry and differential thermogravimetry, scanning electron microscopy, and zeta potential analysis. Factors affecting the adsorption capacities of OVts have been studied. The results indicated that the adsorption mechanism of phenols on both OVts was similar. The adsorption capacities of phenols on 14-6-14-Vt were slightly higher than those on 22-6-6-Vt, and the retention of phenols onto the two OVts followed the order PCP > PMP > P. Hydrophobic, electrostatic, hydrogen bond, and special interactions (cation-pi and pi-pi) played positive roles in the adsorption of phenols onto OVts. The spent OVts were easy to regenerate with ethanol for at least three cycles.