Heterogeneous Fenton-like catalytic degradation of phenazine dye over CeO₂ (CP-2) nanoscale powder

A heterogeneous Fenton-like process was explored for oxidation of phenazine dye using ceria polishing material (CP-2). XRD, SEM, FTIR, UV-vis DRS, and pH_PZC techniques were applied to characterize the catalyst features. The performance of the heterogeneous Fenton-like process was investigated under various parameters (reaction time, pH, H₂O₂ concentration, catalyst dosage, initial dye concentration, temperature of the medium, and inorganic salt content). Results indicated that the main content of CP-2 catalyst was CeO₂ (60-70%) with lower contents of La₂O₃ (30-40%), Pr₆O₁₁ (≤6%), Nd₂O₃, and CaF₂ (≤5%). CP-2 possessed a typical CeO₂ cubic fluorite structure with high content of rare earth oxides (REO) and α-Fe₂O₃. The average crystallite size and band gap energy of CP-2 were found to be 37.2 nm and 3.0 eV, respectively. Over 81.3% of neutral red (NR) oxidation efficiency was achieved in 60 min. Pseudo-first-order kinetic model gave the best fit with an acceptable coefficient of determination R². The activation energy (E_a) was 16.4 kJ/mol suggesting that the degradation reaction proceeded with a low energy barrier and the removal process was feasible, spontaneous, and endothermic. The synergistic effect of Fe- and/or REO-CP-2 and H₂O₂ greatly enhanced the reactive oxygen species (ROS) such as • OH, O₂ •-, ¹O₂ , and HO₂ • for effective oxidation of NR via a heterogeneous Fenton-like process. (author)