Redox cycling of copper mediated by hydrazine: efficient catalyst systems for oxidative degradation of rhodamine B.

Catalytic processes based on Fenton-like reactions on the degradation of organic pollutants have been improved by accelerating the redox cycling of metal ions. This work presents, at first, the results obtained for the heterogeneous degradation of rhodamine B (RhB) by copper ferrite (CuFe2O4) in presence of hydrogen peroxide (H2O2) and hydrazine (N2H4) as redox cycle accelerator. Atomic absorption spectroscopy showed small amounts of Cu2+ are leached from ferrite highlighting the influence of the homogeneous catalysis in the whole process. The data obtained for the homogeneous process using Cu2+ in solution containing both N2H4 and H2O2 indicated such system is highly efficient mineralizing 73% of RhB within only 10 min of reaction and having H2O and CO2 as major products. Using tert-butyl alcohol as radical scavenger, it was confirmed hydroxyl radical (HO•) is the active oxidant species regarding the RhB degradation. The homogeneous catalyst was applied to a real sample of textile effluent spiked with RhB and showed reasonable efficiency, although lower than that obtained for the standard solutions of RhB. This result was assigned to the interference of salts in the medium that react with HO• thus acting as radical scavenger.