Studies on the mechanism of adsorption of methylene blue onto activated carbon using thermodynamic tools

The mechanism of adsorption of methylene blue onto palm kernel shell based activated carbon was studied using thermodynamic approach employing batch adsorption technique. The negative value of the free energy indicates that the process is feasible and spontaneous. The mean value of the entropy of the system was 138.08±21.21 which showed an increased disorder and randomness at the solid solution interface. The results showed that the magnitude of isosteric enthalpy, ΔH obtained (32.09±6.58 kJ mol-1) was clearly indicative of chemisorptions process and the free energy was negative at all temperatures and became more negative with increasing temperature. This behavior is characteristic of both endothermic and chemisorptions process.