Stability of Cu species and zeolite structure on ecological heterogeneous Fenton discoloration-degradation of yellow 5 dye: Efficiency on reusable Cu-Y catalysts

The discoloration-degradation of yellow 5 dye was achieved through the heterogeneous Fenton reaction using Cu-Y catalysts. Cu-Y materials were prepared by an aqueous ion exchange method from the NH₄-Y parent zeolite. The solids are characterized by X-ray diffraction, nitrogen physisorption, EPR and, ²⁷Al and ²⁹Si NMR spectroscopies. Discoloration around 100% with 60% of COD removal was achieved before 90 min at 50°C using the next reaction conditions: 50 mL of colored solution containing 50 ppm of dye, 0.129 mmol of H₂O₂, catalyst mass/volume of solution ratio (g L^-1)= 0.016 and pH = 4-5. The influence of temperature and H₂O₂ concentration was also studied. The discoloration kinetics were modeled using the pseudo-first order reaction. High catalytic activity was observed even after four reaction cycles, which is credited to the good stability of the Cu species and the zeolite structure. Because the Fenton reaction was favored by the acid media provided by the Cu-Y catalyst and temperature, the addition of any acid was not necessary, avoiding the generation of sludge, resulting in an eco-friendly process.