Spectroscopic evidence and molecular simulation investigation of the bonding interaction between lysine and montmorillonite: Implications for the distribution of soil organic nitrogen

Abstract Clay minerals, widespread in natural soil environment, play important roles in the distribution of organics and their utilization by plants and microorganisms. Interface interactions of clay minerals and amino acids are essential for soil and life sciences. The bonding interaction between montmorillonite and lysine was studied systematically and comprehensively in this paper. The montmorillonite-lysine complexes were characterized by X-ray diffraction (XRD), attenuated total reflectance Fourier-transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and molecular simulation investigation. The results of XRD showed that interlayer spacing of montmorillonite increased or decreased with different amounts of lysine indicating two different bonding interactions. Amino acids adsorbed onto montmorillonite through the bonding interaction of electrostatic attraction between negatively charged surface of montmorillonite and NH3+ at the end of lysine on interlayer adsorption aspect as confirmed by XPS and ATR-FTIR spectroscopy. For edge adsorption aspect, the adsorption was through the bonding interaction between COO– group and > AlOH2+/>SiOH2+ groups. Electron localization function calculations for O, Si and Al atoms further demonstrated the bonding interaction of NH3+ groups and the Si O– groups intuitively. These findings give more understandings on the adsorption and distribution of amino acids in different sites of clay minerals.