Highly efficient microwave catalytic oxidation degradation of 4-nitrophenol over magnetically separable NiCo2O4-Bi2O2CO3 composite without adding oxidant

Abstract

A novel magnetically separable NiCo2O4-Bi2O2CO3 composite was developed as an effective microwave catalyst for microwave catalytic oxidation degradation of 4-nitrophenol without adding any oxidant. X-ray photoelectron spectroscopy (XPS) and Roman spectroscopy confirmed that the surface of the NiCo2O4 in NiCo2O4-Bi2O2CO3 composite had a composition containing Co2+, Co3+, Ni2+, and Ni3+. The results show that the NiCo2O4-Bi2O2CO3 microwave catalyst exhibited impressively high catalytic activity with 4-nitrophenol removal ratio of 94.70% in only 1 min and 97.27% within 7 min in this attractive microwave catalytic oxidation degradation approach without adding any oxidant. Moreover, the TOC removal ration can reach up to 93.33%. Importantly, NiCo2O4-Bi2O2CO3 catalyst displays excellent stability with the degradation efficiency as high as 97.31% even after five rounds of degradation process. The impressively high catalytic activity for the degradation of 4-nitrophenol could be ascribed to the production of OH under microwave irradiation. This work builds a new approach for highly effective degradation of wastewater, and provides some guidelines for design of microwave catalysts for microwave catalytic oxidation degradation process.