Organo-montmorillonites for efficient and rapid water remediation: sequential and simultaneous adsorption of lead and bisphenol A

Environmental context Novel materials are increasingly being sought-after to remove metals and organic pollutants from water. We investigated two organo-functionalised montmorillonites for sequential and simultaneous adsorption of lead and bisphenol A. Our findings could lead to new approaches for handling emergency complex pollution events. Abstract Organo-montmorillonites (OMts) modified by two different carbon chain lengths of betaine were used to remove the combined pollution (heavy metal and organic pollutant) from a water environment, sequentially and simultaneously. The properties of OMts were measured with X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetry-Differential Scanning Calorimetry (TG-DSC). The independent adsorption of a single pollutant, direct sequential adsorption, indirect sequential adsorption and simultaneous adsorption of bisphenol A (BPA) and lead ion (Pb2+) onto OMts were investigated. Initial concentrations, reaction time, solution pH and the release amount of pre-adsorbed contaminant in the sequential sorption system were also investigated for the adsorption behaviours of Pb2+ and BPA. Two kinetic models and two adsorption isotherms were applied to explain the adsorption process. The adsorptive mechanism of BPA adsorption onto OMts was ascribed to a hydrophobic interaction, while the mechanism for Pb2+ adsorption was attributed to cation exchange, surface adsorption, electrostatic attraction and complexation from the results of specific surface area Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS). This study might provide valuable information for the application of novel organoclays to the removal of both heavy metal and organics from water.