A comparative study on spinel ferrites-based Fenton-like oxidation systems for efficient treatment of polluted water: Experimental design and modeling

The severely limited reaction rate of Fe³⁺ with hydrogen peroxide (H₂O₂, HP) poses a significant challenge in the Fenton reaction. Despite this, the design and construction of the active site are key factors for developing novel strategies in Fenton-like reactions due to the enhanced activation of HP. In this context, understanding the extent of catalytic activity in ferrites-induced Fenton-like degradation has become a critical area of research. Herein, the oxidation process of Reactive Deep Red 150 (RDR150), as a synthetic common textile dye, was investigated using copper ferrite (CuF₂O₄, CuFO) and cobalt ferrite (CoF₂O₄, CoFO) nanoparticles, which were pursued after being synthesized through simple operational methods. The CuFO/HP process realized a higher RDR150 (20 mg/L) removal efficiency (97.5 %) under the optimized conditions: 0.4 g/L of CuFO and 3.14 mM of HP within 35 min, as determined by the central composite design (CCD) modeling approach. In comparison, the pseudo-first-order RDR150 removal rate was calculated as 0.104 min⁻¹, 3.6 times higher than that of CoFO. The highly efficient catalytic reaction activity was attributed to the larger specific surface area, where CuFO nanoparticles were uniformly dispersed, as well as the synergistic effect arising from the cyclic degradation mediated by redox reactions of ≡Cu(I)/≡Cu(II), ≡Cu(II)/≡Cu(III), and ≡Fe(III)/≡Fe(II) as the active sites. Both radical (i.e., ^•OH and O₂^•−) and non-radical (i.e., ¹O₂) pathways contributed to the Fenton-like degradation of RDR150 in both systems; however, only a minor contribution from ^•OH compared to ¹O₂ and O₂^•− was observed in the CuFO/HP system, as evidenced by the tert-butyl alcohol (TBA) scavenging experiment. Moreover, 71.4 % of the RDR150 removal rate was maintained throughout three cycles of CuFO reuse in the catalytic decomposition of HP. The system demonstrated a consistently high removal rate in the presence of several common anions (Cl⁻, NO₃⁻, CO₃²⁻, and HCO₃⁻), except for SO₄²⁻, demonstrating the stability and adaptability of CuFO for potential application in natural environments. These results underscored the performance metrics of CuFO-activated HP and provided insights into the optimal strategy for enhancing catalytic performance, elucidating the underlying behaviors and mechanisms responsible for promoting its efficiency.