Kinetic and thermodynamic studies of the degradation of methylene blue by photo-Fenton reaction.

Syrian natural magnetite has been utilized for the removal of methylene blue from aqueous solutions by photo-Fenton reaction. Experiments were carried out to evaluate the kinetic and thermodynamic parameters. Pseudo-first order, pseudo-second-order models were used to analyze the kinetic data obtained at different initial MB concentrations and temperatures. The photo-Fenton degradation process of MB is better described by the pseudo-first-order model. The activation energy Ea = 16.89 and 18.02 kJ/mol for MB degradation at concentrations 40 and 80 mg/l respectively, and that suggesting the degradation reaction proceeded with a low energy barrier, the values obtained (ΔG∗, ΔS∗, and ΔH∗) indicate that the process is endothermic and spontaneous.