Title: Preparation and characterization of spermine-exchanged montmorillonite and interaction with the herbicide fluometuron
Abstract: We studied the interaction between the naturally occurring polycation spermine (SPERM) and Na-exchanged SWy-2 Wyoming montmorillonite (Na-SWy-2 Mt) and between spermineexchanged montmorillonite (Mt-SPERM) and the herbicide fluometuron.Mt-SPERM with spermine contents ranging between 0 and 1.2 times the cation exchange capacity (CEC) of Na-SWy-2 were studied by XRD, FTIR and TGA analysis.Spermine was intercalated stoichiometrically into Na-SWy-2 up to the CEC of the clay mineral, resulting in basal spacing of 1.3 nm.TGA analysis indicated that intercalation of spermine into Na-SWy-2 increased the thermal stability of the organic cations and affected the dehydroxylation temperature of the clay mineral.FTIR measurements of Mt-SPERM samples showed the involvement of N-H and C-H groups of spermine in the interaction with the clay mineral.The intensity of the spermine N-H and C-H deformation vibrations increased linearly with the amount of spermine incorporated into Na-SWy-2 up to an amount close to the CEC of the montmorillonite.Structural modeling suggested that the arrangement of spermine cations formed a horizontal monolayer within the interlayer space of SWy-2 with strong interaction between the -NH 3 + and -NH 2 + -groups of spermine and the montmorillonite surface oxygen atoms.Mt-SPERM showed pronounced affinity for the herbicide fluometuron.