Highly efficient microwave catalytic oxidation degradation of p-nitrophenol over microwave catalyst of pristine α-Bi2O3

Microwave catalytic oxidation degradation (MCOD) process over microwave (MW) catalyst of pristine bismuth oxide (Bi2O3) was developed to high-efficiently treat p-nitrophenol (PNP) polluted water. The facile prepared catalyst was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption. The major influencing parameters were investigated and the results showed that the degradation efficiency and the TOC removal ratio reached up to 99.74% and 94.20% respectively in the absence of extra oxidants or air bubbling under the optimal conditions. The PNP degradation efficiency of the seventh round still highly reached 97.80%. Furthermore, the reaction kinetics were studied which were accorded well with pseudo-first-order model and the rate constant was 0.883 min(-1). Moreover, the existence of hydroxyl radical ((OH)-O-center dot) was confirmed by the fluorescent probe technique. The mechanism of the MCOD process was that the Bi2O3 could be excited to generate electron-hole pairs by MW irradiation, then the H2O absorbed on the surface of the catalyst could be transformed into (OH)-O-center dot due to the holes. This work provides a clear demonstration that the MCOD method can high-efficiently degrade PNP and develops new MW catalytic pathways for the treatment of wastewater containing refractory organic contaminants. (C) 2016 Elsevier B.V. All rights reserved.