Simultaneous adsorption of Cd2+ and BPA on amphoteric surfactant activated montmorillonite

The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd2+ from aqueous solution on octadecane-betaine modified montmorillonite (BS-Mt). The characteristics of the obtained materials were analyzed by X-ray diffraction (XRD), Fourier-transform infrared (FOR), Specific surface area (BET) and Scanning electron microscopy/Energy disperse spectroscopy (SEM/EDS), confirming that BS-18 was successfully introduced into Mt. Also, factors including initial solution pH, initial Cd2+/BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd2+ adsorption, whereas had negligible effects on BPA adsorption. In this study, we found that pseudo-second-order model fitted well with the adsorption kinetic studies for both Cd2+ and BPA with an equilibrium time of 24 h. The Cd2+ and BPA adsorption isotherm could be well described by Freundlich model and Langmuir model, respectively. On the basis of kinetic models, the maximum adsorption capacity of Cd2+ in aqueous solution was slightly enhanced after modification, indicating that Cd2+ adsorption on BS-Mt was mainly attributed to direct electrostatic attraction and the chelate reaction, while the dramatic enhancement of maximum adsorption capacity for BPA was due to the hydrophobic interaction. (C) 2015 Elsevier Ltd. All rights reserved.