The ΔG0 value is negative for Rh-B on natural diatomite and it indicates that ad-sorption is spontaneous. The ΔG0 decreases with temperature. Furthermore, better adsorption is obtained at higher temperatures (Khan et al., 2012). The positive values of the enthalpy change (ΔH0) indicates that the adsorption process is endothermic. When ΔH0 is lower than 40 kJ/mol the type of adsorption can be accepted to be a physical process. It indicates that adsorption is physical by nature and involves weak forces of attraction (Khan et al., 2012; Rahchamani et al., 2011). The positive value of ΔS0 shows the increasing randomness at the solid/solution interface during adsorption of RhB on the adsorbents. The positive mean values of ΔS0 may be due to some struc-tural changes in the adsorbate and adsorbents during the adsorption process from the aqueous solution (Unuabonah et al., 2007).