Heterogeneous catalytic oxidation of chromotrope 2B with H2O2 and metal complexes supported on aluminum oxide hydroxide as catalyst

The heterogeneous catalytic oxidation of Chromotrope 2B (C2B) dye with H₂O₂ and the aluminum oxide hydroxide (AlOOH) modified with ammonia complexes of Cu^II, Co^II, Ni^II, and Cr^III (AlOOH/Mⁿ⁺(amm)_m]) as catalysts were studied. The AlOOH/Cu^II(amm)₄] is the most efficient catalyst and therefore it was chosen as the potential catalyst for the oxidative degradation of C2B in an aqueous solution. The AlOOH/Cu^II(amm)₄] was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM), techniques. The rate of reaction was dependent on the type of the metal complex supported on the AlOOH, initial concentration of the dye and H₂O₂, catalyst dose, pH, the concentration of NaCl, and temperature. The catalytic activity of the AlOOH/Mⁿ⁺(amm)_m] according to the kind of metal ion decreased in the order: Cu^II > Co^II > Cr^III > Ni^II. Other catalysts consisting of the AlOOH supported with Cu^II complexed with ethylenediamine, ethanolamine, 1,3 propanediamine, and 1,4 butanediamine, (AlOOH/Cu^II(amine)_m]), were also investigated. The activity of the (AlOOH/Cu^II(amine)_m]) as catalyst according to the type of ligand followed the order: 1,4 butanediamine > 1,3 propanediamine > ethanolamine > ethylenediamine > ammonia. The reaction rate increased with increasing the catalyst dose, concentration of H₂O_2, C2B, and NaCl, pH, and temperature. Since the reusability results for the AlOOH/Cu^II(amm)₄] revealed good stability over seven cycles, it can thus be considered a promising and cost-effective catalyst for the removal of harmful dyes from wastewater.