Synthesis and micro-mechanistic studies of histidine modified montmorillonite for lead(II) and copper(II) adsorption from wastewater

A novel nanocomposite of sodium montmorillonite with L-Histidine (His-Mt), was prepared to remove Pb(II) and Cu(II) from aqueous media. The resulting nanocomposites were characterized by XRD, FT-IR, BET, SEM, TG/DTG, XPS techniques. All characterizations confirmed the anchoring of L-Histidine to Na-Mt, and the packing sequence of His in the interlayer gallery may form a monolayer structure. The His salt obtained a skewed orientation compared to the silicate surface. The single/co-adsorption of Cu(II) and Pb(II) by pure and modified i.e. Na-Mt and His-Mt were carried out by batch adsorption experiments. The maximum adsorption capacity (q(max)) of Pb(II) and Cu(II) by Na-Mt and modified His-Mt was 89.08 mg/g, 23.93 mg/g, and 107.73 mg/g, 30.72 mg/g, correspondingly. The pseudo-second order model (kinetic model) and Langmuir model (isotherm model) well-matched with the adsorption process. The data analysis showed it was an endothermic, favorable and spontaneous process, Cu(II) and Pb(II) showed competitive adsorption in the co-adsorption system. Na-Mt adsorbed M(II) ions by ion exchange mechanism, while M(II) formed complexes with histidine and were adsorbed in the interlayer region or the surface of His-Mt. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.