Degradation of p-nitrophenol (PNP) in aqueous solution by a micro-size Fe0/O3 process (mFe0/O3): Optimization, kinetic, performance and mechanism

•Operating parameters of the mFe0/O3 process were optimized thoroughly.•Degradation pathway of PNP by the mFe0/O3 process was proposed.•Superiority and synergetic action of the mFe0/O3 process was investigated.•Catalytic mechanism of the mFe0/O3 process was investigated thoroughly.

A micro-size Fe0/O3 process (mFe0/O3) was setup to degrade p-nitrophenol (PNP) in aqueous solution, and its key operational parameters (i.e., initial pH, ozone flow rate, and Fe0 dosage) were optimized by the semibatch experiments, respectively. Under the optimal conditions, COD removal efficiency (89.5%) obtained by the mFe0/O3 process was about two times of the sum (44.8%) of COD removal obtained by Fe0 alone and O3 alone. The results suggest that the synergetic effect between O3 and Fe0 in the mFe0/O3 process played a vital role in the degradation of PNP. In addition, treatment efficiency of the mFe0/O3 process also was much higher than some of the present technologies (e.g., Fe0/air process, MnO2/O3 and Al2O3/O3), which confirm the superiority of the mFe0/O3 process. Furthermore, the degradation mechanism and pathway of PNP was proposed according to the analysis results of UV–vis, FTIR, IC and GC–MS. According to the present literature and analysis data of SEM, EDS and XRD analysis, it can be concluded that the high-efficient mFe0/O3 process was mainly resulted from the combination of homogeneous or heterogeneous catalytic ozonation, Fenton-like reaction, adsorption and precipitate. Therefore, the mFe0/O3 process was a promising technology for the refractory industrial wastewater.

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