Silylating agents grafted onto silica derived from leached chrysotile

Silica from leached chrysotile fibers (SILO) was silanized with trialkoxyaminosilanes to yield inorganic-organic hybrids designated SILx (x = 1-3). The greatest amounts of the immobilized agents were quantified as 2.14, 1.90, and 2.18 mmol g(-1) on SIL1, SIL2, and SIL3 for -(CH2)(3)NH2, -(CH2)(3)NH(CH2)(2)NH2, and -(CH2)(3)N-H(CH2)(2)NH(CH2)(2)NH2 groups attached to the inorganic support. The infrared spectra for all modified silicas showed the absence of the Si-OH deformation mode, originally found at 950 cm(-1), and the appearance of asymmetric and symmetric C-H stretching bands at 2950 and 2840 cm(-1). Other important bands associated with the organic moieties were assigned to nu (as)(NH) at 3478 and nu (sym)(NH) at 3418 cm(-1). The NMR spectrum of the solid precursor material suggested two different kinds of silicon atoms: silanol and siloxane groups, between -90 and 110 ppm; however, additional species of silicon that contain the organic moieties bonded to silicon at -58 and -66 ppm appeared after chemical modification. These modified silicas showed a high adsorption capacity for cobalt and copper cations in aqueous solution, in contrast to the original SILO matrix, confirming the unequivocal anchoring of silylating agents on the silica surface. (C) 2001 Academic Press.