ADSORPTION OF ASSOCIATING MOLECULES IN MICROPORES AND APPLICATION TO WATER ON CARBON

A general theory for the adsorption of self-associating molecules in m icroporous structures is developed. The approach is similar to the ''c hemical'' interpretation of nonideality of vapor and liquid phases. Th e theory displays Type 5 isotherm behavior and can explain Types I and 5 transition. Isothermal data are represented by only three parameter s: Henry's law constant, saturation capacity, and reaction constant fo r ''cluster'' formation in the micropores. When isotherms at different temperatures are available, the theory can be used with five temperat ure-independent parameters to describe the entire phase behavior inclu ding the heat of adsorption. Water adsorption on activated carbon, the most common display of Type 5 behavior is used to test the theory. An alysis of several data sets indicates that the theory can closely corr elate data, provide physically meaningful parameter values in line wit h carbon properties, and it is highly effective in correlating tempera ture variation. The reaction enthalpy for water dimerization in the ca rbon micropores is lower than that in vapor phase. This preliminary co nclusion with the theory needs to be supported with more accurate data when available.