The synergy of zinc oxide supported magnetic cobalt ferrite: Efficient boosting the peroxymonosulfate activation towards the refractory organic pollutants elimination

Herein, we report the construction of ZnO-supported spinel CoFe2O4 (CFO) nanocomposites, i.e., CFZ, by a facile hydrothermal method, as an effective peroxymonosulfate (PMS) activator for the degradation of organic pollutants. The optimized hybrid catalyst CFZ 1:1 showed excellent enhancement in efficiency towards BPA decontamination as compared to the single metal oxides alone and the mixing of CFO and ZnO powder. Under the conditions of 0.5 g.L-1 CFZ 1:1, 0.2 g.L-1 PMS, and non-adjusted pH, the removal efficiencies of 95% and 67% were attained for BPA (20 mg.L-1) and TOC within 20 mins reaction. The catalytic decontamination process could adapt to a wide pH range (pH5 – pH9) and showed negligible influence by several common anions. Interestingly, the presence of Cl- ions accelerated the BPA removal rate (k = 0.303 min-1 by adding 50 mM Cl), suggesting that the CFZ 1:1/PMS system could function well under salty conditions. Based on the quenching experiments and electron paramagnetic resonance (EPR) characterization, the generation of nonradical singlet oxygen (1O2), sulfate radical anion (SO4•-), and hydroxyl radical (•OH) was responsible for BPA degradation in which 1O2 was hypothesized to be the dominant reactive oxygen species. Beside the separately efficient removal of several pollutants represent for dyes, antibiotics, and POPs, CFZ 1:1/PMS system could almost completely eliminate mixed pollutant solution containing BPA, rhodamine B, and tetracycline after a short time 20 mins. The CFZ 1:1/PMS system also remained highly stable and robust for 4 consecutive runs with over 80% BPA removal and minimal leaching of metal ions. Overall, the results enlightened new insights into the design and development of composite catalysts for the removal of persistent pollutants from wastewater.