Abstract
Gravimetric water adsorption experiments (T = 5, 20 and 35 oC and 0 < P/Po < 0.95) were
performed for comparative purposes on several chemically and structurally distinct samples of
single-walled carbons nanotubes including two activated carbon samples. The isotherms
followed the type V curve and were fitted to a semi-empirical model which allowed
distinguishing with statistical confidence the adsorptive contributions of primary sites and
micropores (referred to here as pseudo-experimental isotherms). The isosteric heats of total water
adsorption calculated from experimental isotherms ranged between 46 to 58 kJ/mol. The same
calculations were performed on the separated adsorptive components: functional groups and
micropore isotherms, and were found to be 0.5 to 16 kJ/mol and 1 to 3 kJ/mol, respectively.
These values are similar to those available in the current literature reportedly estimated by
calorimetric and molecular simulation techniques. From semi-empirical modeling, we discovered
that we were able to reliably estimate temperature sensitive water-specific sample properties
such as the concentration of primary sites (directly related to % O), the size of water clusters
aggregating on primary sites (inversely related to % O) and those filling micropores (directly
related to dominant pore size) and the equilibrium constants. We conclude that our approach is
useful in interpreting experimental water adsorption thus aiding purely simulation based methods
of studying the behavior of water in nanocarbons.
