Kinetics and mechanism of the heterogeneous catalyzed oxidative decolorization of Acid-Blue 92 using bimetallic metal-organic frameworks.

The kinetics study of the oxidative decolorization of Acid-Blue 92 has been investigated by hydrogen peroxide catalyzed with bimetallic metal-organic frameworks. The used metal-organic frameworks (MOF) are [Ph3SnCu(CN)2·L] where L=pyrazine (pyz) 1, methylpyrazine (mepyz) 2, 4,4'-bipyridine (bpy) 3, trans-1,2-bis(4-pyridyl)ethene (tbpe) 4 or 1,2-bis(4-pyridyl)ethane (bpe) 5. The reaction was followed by conventional UV-Vis spectrophotometer at λmax=571 nm. The reaction exhibited first-order kinetics with respect to [dye] and [H2O2]. The reactivity of the catalysts depends on the type of the medium and thereafter decreases in strong alkaline media. Addition of NaCl enhances the reaction rate. Also, the irradiation of the reaction with UV-light enhanced the rate of AB-92 mineralization by about 86.9%. The reaction was entropy-controlled as confirmed by the isokinetic relationship. A reaction mechanism was proposed with the formation of free radicals as an oxidant.