Catalytic ozonation performance of graphene quantum dot doped MnOOH nanorod for effective treatment of ciprofloxacin and bromate formation control in water

A catalyst GQDs@MnOOH was successfully synthesized by attaching graphene quantum dots (GQDs) on the surface of MnOOH nanorods to boost catalytic ozonation of antibiotic, exemplified by ciprofloxacin (CIP). The result demonstrated that the GQDs@MnOOH/O3 system had the greatest CIP removal effectiveness, followed by that of MnOOH/O3 and O3 only. The 0.02 mM CIP was degraded with 99.9% efficiency in 30 min in the presence 9.6 mg L-1 of O3 catalyzed by 12.5 mg L-1 of GQDs@MnOOH. The kinetic rate constants were in the order: GQDs@MnOOH/O3 (0.161 min-1) > MnOOH/O3 (0.079 min-1) > O3 (0.055 min-1). The GQDs@MnOOH could enhance CIP degradation and inhibit BrO3- formation in different water sources. Results of scavenger and electron paramagnetic resonance (EPR) experiments demonstrated that oxygen radical (O2 center dot-), singlet oxygen (1O2), and hydroxyl radicals (center dot OH) were involved in CIP degradation by the GQDs@MnOOH/O3 system. Accordingly, the degradation pathways of CIP and mechanism of catalytic ozonation over GQDs@MnOOH were investigated and proposed. This research is expected to shed light on the connection between carbonaceous material and metal hydroxide in catalytic ozonation.

Automated summary

A catalyst GQDs@MnOOH was synthesized to enhance the catalytic ozonation of the antibiotic ciprofloxacin (CIP). The GQDs@MnOOH/O3 system showed the highest CIP removal effectiveness compared to MnOOH/O3 and O3 only. The degradation of 0.02 mM CIP reached 99.9% efficiency in 30 min using 9.6 mg L-1 of O3 catalyzed by 12.5 mg L-1 of GQDs@MnOOH. The GQDs@MnOOH enhanced CIP degradation and inhibited the formation of BrO3- in different water sources. Oxygen radical (O2 center dot-), singlet oxygen (1O2), and hydroxyl radicals (center dot OH) were involved in CIP degradation by the GQDs@MnOOH/O3 system.