Results from thermal analyses of sodium and calcium montmorillonites containing adsorbed benzoic acid are described. Based on these results, adsorption sites and thermal desorption processes are elucidated. Desorption of interlayer water is affected by the presence of benzoic acid, which disrupts cation-water interactions. Multiple benzoic acid desorption sites are indicated, which have properties that depend on the clay interlayer cation. Benzoic acid desorption occurs at higher temperatures for clays containing calcium ions compared to those containing sodium ions, presumably due to stronger interactions between the adsorbate and calcium ions. Benzoic acid desorption profiles, as well as the detection of decomposition products, suggest that benzoic acid persists on clays to temperatures as high as 550 degrees C. Above 300 degrees C, benzoic acid decomposes, yielding benzene and carbon dioxide. (C) 2015 Elsevier B.V. All rights reserved.