High resolution argon and nitrogen adsorption assessment of the surface heterogeneity of carbosils

Carbon mineral adsorbents are promising materials for a wide range of applications due to the dual polar-apolar properties of their surfaces. The changes in surface properties of a mineral support depend on the way in which carbon is organized on that mineral surface. In the present work, a set of carbosils has been synthesized, by increasing exposition duration to dichloromethane at 550 degrees C. The corresponding variations in surface properties were studied using high resolution quasi-equilibrium adsorption of nitrogen and argon. For a given gas, the derivative of adsorption isotherm, taken with respect to the logarithm of relative pressure, can be considered as a finger print of surface heterogeneity. Quantitative information on adsorption energy distribution was also obtained by applying the derivative isotherm summation method. The combined qualitative and quantitative information makes it possible to draw conclusions about the topography and adsorption energy distribution of pyrocarbon deposit on the mineral surface. (C) 1998 Elsevier Science Ltd. All rights reserved.