This letter discusses the discrepancies in thermodynamic studies in a recent article by Bouberka et al. Also presented is the significance of the separation factor R-L used to express the essential characteristics of Langmuir isotherm. In addition, the incorrect forms of the two kinetics rate equations, the pseudo-first-order and pseudo-second-order equations used by the authors, are also mentioned. (C) 2007 Elsevier B.V. All rights reserved.