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 NiFe 2 O 4 /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 NiFe 2 O 4 /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 Fe 3+ /Fe 2+ redox cycle by complexing with Fe 3+ on NiFe 2 O 4 /SEP, and then accelerated the formation of reactive oxygen species. In the presence of NiFe 2 O 4 /SEP, the high oxidation potential of •OH and •O 2 - contributed to an excellent TOC removal rate. Meanwhile, NiFe 2 O 4 /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 NiFe 2 O 4 /SEP+O 3 system in 60 min. These findings indicated the good potential of NiFe 2 O 4 /SEP for practical applications in industrial wastewater treatment.