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Isotherms were found to be of type I, typical of high sugar foods. Study on temperature dependence of isotherms showed that above water activities of 0.6, moisture content was higher at higher temperature. This was explained by endothermic dissolution of sugar at high water activities. Iglesias and Chirife, Halsey, BET and GAB equations were tested to fit the data. Monolayer moisture contents for the three foods were determined from BET and GAB equations. In both models, monolayer moisture was found to decrease with increasing temperature. Isosteric heat of sorption data from the isotherms at two temperatures, revealed that strength of interactions between water vapor and adsorbent increased with moisture content.

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Adsorption behaviours of some structurally related aromatic heterocyclic compounds at an high-area carbon-cloth material have been investigated in relation to waste-water purification. Adsorption processes were followed by monitoring the concentration of adsorbates in a specially designed cell using an in situ UV spectrophotometric method. The rates of adsorption were compared by treating the data according to first-order kinetics. Among the seven heterocyclic compounds studied, thiophene was found to exhibit the highest adsorption rate. This was attributed to the presence of the electron-donative S heteroatom in the structure of this compound. The influences of the dipole moment, the orientation at the C-cloth surface and the size of the heterocyclic adsorbate compound, as well as the type of heteroatom in the ring and the adsorbates’ hydration parameters, on the extent of adsorption of these compounds at the C-cloth were investigated.