The adsorption of formaldehyde (HCHO) at very low vapor concentration (zero
surface coverage) is studied on several carbon materials by using inverse
gas-solid chromatography (IGC). The adsorption process is carried out in th
e Henry's law region. Therefore, the specific retention volumes, V-s, allow
the determination of the standard enthalpy of adsorption, Delta H degrees(
A), using the linear relationship between In V-s vs 1/T. Nevertheless two l
inear plots are obtained for the adsorption of HCHO on these carbon materia
ls. Several experiments have been designed in order to determine the physic
al meaning of these Linear plots. The general conclusion is that they are p
roduced by a temperature-dependent mechanism which allows the adsorption to
occur in smaller pores at lower temperatures and in larger ones at higher
temperatures.