Results and discussionThe measured adsorption isotherms were described using the (1) Langmuir equation a be 1+be, and (2) Freundlich equation, a=ke," where a (mol/g) is the amount of solute adsorbed per unit weight of adsorbent, C. (mol/L) is the equilibrium concentration of solute, a (mol/g) is the amount of solute adsorbed per unit weight of adsorbent, required for monolayer coverage of the surface, b (L/mol) is a constant related to the heat of adsorption, k (mol/g)(L/mol) and n Freundlich constants. The adsorption isotherms from aqueous solutions of benzoic and acetic acids different temperatures are presented in figure la) and figure 1b). There are different behaviours depending on temperature for the both adsorbates.