Enhancing acid orange II degradation in ozonation processes with CaFe(2)O(4) nanoparticles as a heterogeneous catalyst

This study used CaFe(2)O(4) nanoparticles as a catalyst for ozonation processes to degrade Acid Orange II (AOII) in aqueous solution. The study compared heterogeneous catalytic ozonation (CaFe(2)O(4)/O(3)) with ozone treatment alone (O(3)) at different pH values (3–11), catalyst dosages (0.25–2.0 g L(−1)), and initial AOII concentrations (100–500 mg L(−1)). The O(3) alone and CaFe(2)O(4)/O(3) systems nearly completely removed AOII's color. In the first 5 min, O(3) alone had a color removal efficiency of 75.66%, rising to 92% in 10 min, whereas the CaFe(2)O(4)/O(3) system had 81.49%, 94%, and 98% after 5, 10, and 20 min, respectively. The O(3) and CaFe(2)O(4)/O(3) systems degrade TOC most efficiently at pH 9 and better with 1.0 g per L CaFe(2)O(4). TOC removal effectiveness reduced from 85% to 62% when the initial AOII concentration increased from 100 to 500 mg L(−1). The study of degradation kinetics reveals a pseudo-first-order reaction mechanism significantly as the solution pH increased from 3 to 9. Compared to the O(3) alone system, the CaFe(2)O(4)/O(3) system has higher k values. At pH 9, the k value for the CaFe(2)O(4)/O(3) system is 1.83 times higher than that of the O(3) alone system. Moreover, increasing AOII concentration from 100 mg L(−1) to 500 mg L(−1) subsequently caused a decline in the k values. The experimental data match pseudo-first-order kinetics, as shown by R(2) values of 0.95–0.99. AOII degradation involves absorption, ozone activation, and reactive species production based on the existence of CaO and FeO in the CaFe(2)O(4) nanocatalyst. This catalyst can be effectively recycled multiple times.