Bicarbonate enhanced heterogeneous activation of peroxymonosulfate by copper ferrite nanoparticles for the efficient degradation of refractory organic contaminants in water

Nowadays, the treatment of residual refractory organic contaminants (ROCs) is a huge challenge for environmental remediation. In this study, a potential process is provided by copper ferrite catalyst (CuFe2O4) activated peroxymonosulfate (PMS, HSO5- in the bicarbonate (HCO3-) enhanced system for efficient removal of Acid Orange 7 (AO7), 2,4-dichlorophenol, phenol and methyl orange (MO) in water. The impact of key reaction parameters, water quality components, main reactive oxygen species (ROS), probable degradation mechanism, rational degradation pathways and catalyst stability were systematically investigated. A 95.0% AO7 (C-0 = 100 mg L-1) removal was achieved at initial pH (pH(0)) of 5.9 +/- 0.1 (natural pH), CuFe2O4 dosage of 0.15 g L-1, PMS concentration of 0.98 mM, HCO3- concentration of 2 mM, and reaction time of 30 min. Both sulfate radical (SO4-center dot) and hydroxyl radical ((OH)-O-center dot) on the surface of catalyst were proved as the predominant radical species through radical quenching experiments and electron paramagnetic resonance (EPR) analysis. The buffer nature of HCO3 was partially contributed for the enhanced degradation of AO7 under CuFe2O4/PMS/HCO3- system. Importantly, according to C-13 nuclear magnetic resonance (NMR) and EPR analysis, the positive effect of bicarbonate may be mainly attributed to the formation of peroxymonocarbonate (HCO4-), which may enhance the generation of (OH)-O-center dot. The magnetic CuFe2O4 particles can be well recycled and the leaching concentration of Cu was acceptable (<1 mg L-1). Considering the widespread presence of bicarbonate in water environment, this work may provide a safe, efficient, and sustainable technique for the elimination of ROCs from practical complex wastewater.

Automated summary

In this study, a potential process using a copper ferrite catalyst activated peroxymonosulfate (PMS) system was developed for efficient removal of residual refractory organic contaminants (ROCs) in water. The key reaction parameters, water quality components, main reactive oxygen species (ROS), probable degradation mechanism, rational degradation pathways, and catalyst stability were investigated. The results showed that the system achieved a 95.0% removal of Acid Orange 7 (AO7) at specific conditions, and both sulfate radical and hydroxyl radical were identified as the predominant radical species. The presence of bicarbonate was found to enhance the degradation efficiency, and the CuFe2O4 particles demonstrated good recyclability with acceptable leaching concentration of Cu. This work may provide a safe and sustainable technique for the elimination of ROCs from complex wastewater.