Kaolinite-polymer compounds by grafting of 2-hydroxyethyl methacrylate and 3-(trimethoxysilyl)propyl methacrylate

Novel kaolinite-polymer solids containing methacrylate groups were prepared by functionalization of the Brazilian Sao Simao kaolinite with the monomers 2-hydroxyethyl methacrylate (HEMA) and 3-(trimethoxysilyl) propyl methacrylate (TMSPM). Functionalization involved reflux of the monomers in the presence of kaolinite previously intercalated with dimethylsulfoxide (DMSO). HEMA and TMSPM effectively displaced DMSO molecules from the clay mineral interlayer, forming Al-O-C bonds in organic-inorganic hybrid matrices. The resulting materials were characterized by powder X-ray diffraction, thermal analysis, infrared spectroscopy and TEM analysis. Powder X-ray diffraction evidenced the intercalation of DMSO, and its substitution by HEMA and TMSPM. Thermal analyses indicated that HEMA- and TMSPM-functionalized kaolinite materials were thermally stable up to 300 degrees C. The shift of the infrared bands due to interlayer hydroxyl groups and the presence of bands due to characteristic vibrations of the methacrylate groups (3349, 3331, 3290, and 1589 cm(-1)) also confirmed the functionalization of the kaolinite with the monomers. The ability of both monomers to graft methacrylate groups onto kaolinite interlayer space was also analyzed. The solids obtained were used as adsorbents of dye methylene blue (MB), showing that the clay nanocomposites could remove the dye more efficiently than the isolated precursors (pure kaolinite and the polymers) separately. The kinetics of the process followed a pseudo second order model and equilibrium fitted well to the Freundlich model.