Homogenous catalytic ozonation of aniline aerofloat collector by coexisted transition metallic ions in flotation wastewaters

Abstract Aniline aerofloat (AAF) is a biologically persistent flotation collector with potential hazards to aquaic lives and humans. In flotation wastewaters, transition metallic ions usually coexist with residual reagents. Thus, the homogenous catalytic ozonation can be formed while flotation wastewaters are treated by ozone. In this work, the catalytic ozonation of AAF collector was evaluated with transition metallic ions (Fe2+, Fe3+, Cu2+, Pb2+ and Zn2+). Particularly, the effects of Fe2+ dosage, initial pH and O3 dosage on the Fe2+ catalytic ozonation of AAF were studied. The AAF mineralization was evaluated by measuring the TOC, SO42- and NO3‒ concentrations. The degradation rate followed the order O3/Fe2+>O3/Fe3+>O3/Cu2+>O3/Pb2+>O3/Zn2+≈O3-alone. The reduction of EE/O values for AAF degradation reached 4.75‒44.15% by introducing transition metallic ions. For five metallic ions, Fe2+ ions had the highest catalytic activity. At the Fe2+ dosage of 10 mg L‒1, the O3/Fe2+ achieved an increase of 31.15% for the degradation rate and of 42.26% for the AAF mineralization compared to O3-alone. The SPE/GC‒MS analysis showed that the byproducts generated by O3-alone were quite different from those by O3/Fe2+, and toxic aniline and phenol were not detected in the O3/Fe2+ system. The results indicated that transition metallic ions could well enhance the ozonation of flotation reagents with lower energy consumption.