Surface properties of mesoporous carbon-silica gel adsorbents

Carbon/silica (carbosil) samples prepared utilizing mesoporous silica gel ( Si-60) modified by methylene chloride pyrolysis were studied by nitrogen ad sorption, quasi-isothermal thermogravimetry, p-nitrophenol adsorption from aqueous solution, and H-1 NMR methods. The structural characteristics and o ther properties of carbosils depend markedly on the synthetic conditions an d the amount of carbon deposited. The changes in the pore size distribution with increasing carbon concentration suggest grafting of carbon mainly in pores, leading to diminution of the mesopore radii. However, heating pure s ilica gel at the pyrolysis temperature of 550 degrees C leads to an increas e in the pore radii. The quasi-isothermal thermogravimetry and H-1 NMR spec troscopy methods used to investigate the water layers on carbosils showed a significant capability of carbosils to adsorb water despite a relatively l arge content of the hydrophobic carbon deposit, which represents a nonunifo rm layer incompletely covering the oxide surface. (C) 2000 Academic Press.