Carbonaceous particle hydration

Microgravimetric measurements of the hydration of several different black carbons or soots and a series of commercial carbon blacks have been carried out, over a relative humidity range of 20–85%, in an extension of earlier work with the model n-hexane soot. All adsorption isotherms are of type III and were analyzed by the use of the Dubinin–Radushkevich (DR) equation which, although applicable over a limited range of intermediate relative humidity values, allows identification of chemisorption limit and onset of multilayer formation. While surface area determines the maximum adsorption possible for a given type, surface functionalities are determinative at lower humidity and are characteristic of the soot-producing fuel. Aging of carbon particles and oxygen chemisorption as well as O2 physisorption strongly influence the extent of hydration for those soots studied, such as JP-8 aviation and diesel fuels. Infrared spectra confirm the surface oxidation of JP-8 soot by its reaction with O3, a reaction of probable atmospheric importance, as underlying its increased hydration.