Layered inorganic/organic mercaptopropyl pendant chain hybrid for chelating heavy cations

Heavy metal sorbents with uptake capacities for divalent cadmium and lead cation removal from aqueous solutions have been synthesized by grafting mercaptopropyltrimethoxysilane onto the surface of two different precursors obtained from lamellar ilerite, its acidic and the cetyltrimethylammonium exchanged forms. The organofunctionalization was carried out by two different procedures: reflux and solvent evaporation methodologies. Elemental analysis data based on carbon content gave 1.37 and 3.53 mmol of organic pendant groups per gram of hybrid by the reflux method, when starting from acidic ilerite and the surfactant form. X-ray diffraction corroborated the maintenance of the original crystallinity. Infrared spectroscopy and nuclear magnetic resonance for 29Si and 13C nuclei are in agreement with the success of the proposed method. The sulfur basic centers attached to the lamellar structure are used to coordinate both cations at the solid/liquid interface. The isotherms were obtained through the batchwise process and the experimental data were adjusted to the Freundlich model. The maximum sorption capacities of 5.55 and 5.12 mmol g−1 for lead and 6.10 and 7.10 mmol g−1 for cadmium were obtained for organofunctionalized ilerite and its surfactant form, synthesized by reflux methodology. This behavior suggested that these hybrids could be employed as promising sorbents with a polluted system.

Graphical abstractCrystalline lamellar silicate RUB-18 was immobilized with mercaptopropyl groups at the surface and then used as support for cadmium and lead removal from aqueous solutions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthetic methodology requires intercalation. ► Organofunctionalized ilerite compound as sorbent. ► Active mercaptopropyl groups remove cations. ► High maximum sorption capacity for cadmium.