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

• Montmorillonite was modified with green and environment-friendly Histidine salt. • His-Mt is proved to be a high-efficiency adsorbent for removal of heavy metal ions. • Maximum adsorption capacity for Pb(II) and Cu(II) with His-Mt is 107.73 mg/g and 30.72 mg/g. • Ion exchange is main mechanism by Na-Mt by forming Pb(CO 3) 2 or Cu(OH) 2. 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. [ABSTRACT FROM AUTHOR]