Magnetically separable NiFe2O4/sepiolite catalyst for enhanced ozonation treatment of quinoline and bio-treated coking wastewater in a catalytic ozonation system

In a quest to eliminate the bio-refractory organic pollutants in industrial wastewater, the NiFe2O4/SEP composites were synthesized via a sol-gel method and investigated by XRD, SEM, XPS, FTIR, VSM. The TOC removal increased from 16.82% to 69.35% in NiFe2O4/SEP+O-3 system using quinoline as a target contaminant after 30 min, which is about 4.12 times as that in O-3 system. The evolution of acetic acid, oxalic acid and formic acid in quinoline degradation was analyzed, saturated carboxylic acids were inertia to ozone molecules. However, 93.54% of oxalic acid was removed after 10 min, and 77.66% of acetic acid was degraded after 30 min in catalytic ozonation. The generation of small molecular organic acids could promote the Fe3+/ Fe2+ redox cycle by complexing with Fe3+ on NiFe2O4/SEP, and then accelerated the formation of reactive oxygen species. In the presence of NiFe2O4/SEP, the high oxidation potential of center dot OH and center dot O-2(-) contributed to an excellent TOC removal rate. Meanwhile, NiFe2O4/SEP was proved to be active for bio-treated coking wastewater in catalytic ozonation. The naturally fluorescent constituents in bio-treated coking wastewater were almost entirely removed by NiFe2O4/SEP+O-3 system in 60 min. These findings indicated the good potential of NiFe2O4/SEP for practical applications in industrial wastewater treatment. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.