Microwave-enhanced catalytic degradation of 2-nitrophenol on alumina-supported copper oxides

Abstract

Abstract Copper oxides/alumina catalyst was prepared using impregnation method. It was characterized by XRD, SEM and FTIR. The crystallography of the catalyst indicated presence of bulk copper oxide in the catalyst matrix. SEM showed different sizes of ensembles of the active component on the support. The catalyst was tested in degradation of 2-nitrophenol from its aqueous solution (200 mg/l) using hydrogen peroxide as an oxidant under microwave irradiation obtained at 2450 MHz and 300 W. The effects of catalyst dosage (0–30 g/l), hydrogen peroxide (0–30 mM), pH (4 or 10) and temperature (40–60 °C) on the degradation were studied. Catalyst dosage of 5 g/l was observed to be the optimum required in generation of hydroxyl radicals for the degradation at 60 °C. The degradation was higher in acidic than in basic medium. This was associated with radical scavenging effect of bicarbonate in the basic media. About 97% 2-nitrophenol removal corresponding to 79% TOC removal rate was achieved at 60 °C. The apparent activation energy of 2-nitrophenol degradation was estimated to be 73.1 kJ/mol. The catalyst was subjected to several experimental runs and found to have limited stability. The nitrophenol degradation declined from 97 to 93% after four consecutive experimental runs.