This book deals with the thermodynamic parameters of the adsorption of dyes specially methylene blue (MB) on different low-cost adsorbents. The comparison of enthalpy change (ΔH°) and entropy change (ΔS°) clearly divides the adsorbents into two groups, namely, inert or inorganic and natural or lignocellulosic adsorbents. The former group follows the van’t Hoff equation and no compensation effect is required in the computation of enthalpy and entropy changes. On the other hand the second group requires the consideration of compensation effect which is generally overlooked by almost all of the authors. Although the calorimetry is the best solution to get the reliable values of thermodynamic parameters in almost all systems, a quick estimate is generally obtained from the equilibrium constant especially in adsorption studies. It might be acceptable in inorganic adsorbents due to low compensation temperature but it would be more erroneous in lignocellulosic adsorbents hence their contribution need be accounted for to get more reliable results.