Preparation and characterization of spermine-exchanged montmorillonite and interaction with the herbicide fluometuron

1 We studied the interaction between the naturally occurring polycation spermine (SPERM) and 2 Na-exchanged SWy-2 Wyoming montmorillonite (Na-SWy-2 Mt) and between spermine3 exchanged montmorillonite (Mt-SPERM) and the herbicide fluometuron. Mt-SPERM with 4 spermine contents ranging between 0 and 1.2 times the cation exchange capacity (CEC) of 5 Na-SWy-2 were studied by XRD, FTIR and TGA analysis. Spermine was intercalated 6 stoichiometrically into Na-SWy-2 up to the CEC of the clay mineral, resulting in basal 7 spacing of 1.3 nm. TGA analysis indicated that intercalation of spermine into Na-SWy-2 8 increased the thermal stability of the organic cations and affected the dehydroxylation 9 temperature of the clay mineral. FTIR measurements of Mt-SPERM samples showed the 10 involvement of N-H and C-H groups of spermine in the interaction with the clay mineral. The 11 intensity of the spermine N-H and C-H deformation vibrations increased linearly with the 12 amount of spermine incorporated into Na-SWy-2 up to an amount close to the CEC of the 13 montmorillonite. Structural modeling suggested that the arrangement of spermine cations 14 formed a horizontal monolayer within the interlayer space of SWy-2 with strong interaction 15 between the -NH3 and -NH2groups of spermine and the montmorillonite surface oxygen 16 atoms. Mt-SPERM showed pronounced affinity for the herbicide fluometuron. 17 18