Microstructural modification of organo‐montmorillonite with Gemini surfactant containing four ammonium cations: molecular dynamics (MD) simulations and adsorption capacity for copper ions

Abstract

AbstractBACKGROUNDCopper is a heavy metal that is widely available in nature and has attracted people's attention because of its toxicity and difficult biodegradability. Using modified montmorillonite to adsorb copper ions (Cu2+) was widely adopted because of its simple operation, high efficiency, and easy availability.RESULTSNa‐montmorillonite (Na‐Mt) was modified through a Gemini surfactant (containing four ammonium cations) to explore the adsorption capacity for Cu2+ in aqueous media. The resulting product is called G‐Mt. FT‐IR XRDBET results indicated that Gemini surfactant has significantly intercalated into the montmorillonite interlayers. The results ofbatch adsorption experiments presented that the amount of adsorbed (qe) depend on pH value and qe (G‐Mt) can reach to 29.30 mg/g, which was greater than that of Na‐Mt (25.30 mg/g) when pH is 6.0 and initial Cu2+ concentration is 75 mg/L. The experimental data matched well with Langmuir isotherm. The thermodynamic analysis implied that adsorption of Cu2+ was endothermic and a spontaneous process. Molecular dynamics (MD) models were carried out to investigate the microstructure and kinetic information of Gemini cations in the interlayer of G‐Mt. The results elucidated that the distribution and interaction characteristic of ammonium cations of Gemini surfactant including four ammonium cations were completely different from that of the quaternary ammonium salts containing asingle ammonium cation.CONCLUSIONGenerally, considering the comprehensive performances, polyamine Gemini surfactant to modify montmorillonite can improve its ability to adsorb Cu2+. The micro environment in the interlayer space and adsorption properties of G‐Mt on Cu2+, which will improve the potential utilization of G‐Mt in soil remediation or wastewater treatment. © 2019 Society of Chemical Industry