Simultaneous adsorption of Cd(2+) and BPA on amphoteric surfactant activated montmorillonite

Abstract The study mainly investigated the simultaneous adsorption of bisphenol A (BPA) and Cd 2+ 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 (FTIR), 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 Cd 2+ /BPA concentration, contact time and adsorbent dosage on the adsorption processes were shown to be crucial for Cd 2+ 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 Cd 2+ and BPA with an equilibrium time of 24 h. The Cd 2+ 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 Cd 2+ in aqueous solution was slightly enhanced after modification, indicating that Cd 2+ 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.