(?) Dubinin-Radushkevich: is a model similar to Langmuir, but in general form. The only difference, the surface not homogeneous or constant adsorption potential 49 with equation:
ln??Q_e=ln??K_(D-R)-??^2 ? ? (11)
Plot the relation ln Q vs. ?2 (? = RT ln 1+ (1/C_e)), give a straight line (R2 = 0.963, 0.936 and 0.874) for Br.G, To.B and Tr.B dyes (Fig.2c). E (KJ/mol) is the average free energy need for adsorption of one mole of the adsorbate to transfer to the surface of adsorbent (Ergene et el., 2009) was calculated with the help of equation (Hobson, 1969): E=1/?(-2?) . The values of E were 2.78, 2.96 and 2.39 KJ/mol, proving that adsorption was not dominated by the chemical ion exchange mechanism because E is not between 8 and16 KJ/mol and E smaller than 8 KJ/mol, the physical forces dominate (Rafatullah et el., 2009).