Dramatically enhanced Fenton oxidation of carbamazepine with easily recyclable microscaled CuFeO 2 by hydroxylamine: Kinetic and mechanism study

Abstract

Abstract In this study, an inorganic reductant hydroxylamine was used to enhance the Fenton degradation of carbamazepine by easily recyclable microscaled CuFeO2 in a wide pH range (pH 4.0–9.0). It was found that the addition of hydroxylamine could dramatically enhance the degradation rate and TOC removal of carbamazepine, better than other reductants such as benzoquinone and ascorbic acid. In the CuFeO2-H2O2 Fenton system, only 31% CBZ (50 μmol L−1) was removed at pH of 7.0 in 60 min in the presence of 1.0 g L−1 CuFeO2 and 20 mmol L−1 H2O2, while CBZ can be nearly completely removed in 60 min after the addition of 0.1 mmol L−1 hydroxylamine under the similar conditions. Moreover, CBZ degradation followed the pseudo first-order kinetics in the CuFeO2-H2O2 Fenton system, while in the hydroxylamine enhanced CuFeO2-H2O2 Fenton system, CBZ degradation followed the pseudo second-order kinetics. In the CuFeO2-H2O2 Fenton system, t1/2 value for CBZ degradation was calculated as 114.4 min and the value was greatly decreased to 1.8 min after the addition of hydroxylamine. This hydroxylamine induced dramatic carbamazepine degradation enhancement could be attributed to the hydroxylamine enhanced Fe(III)/Fe(II) and Cu(II)/Cu(I) redox cycles. Hydroxyl radicals were the primary radical species responsible for the carbamazepine degradation. As a microscaled catalyst, micro-CuFeO2 can be easily recovered by gravity settlement and exhibited good catalytic stability during six successive degradation cycles. Therefore, the couple of CuFeO2-H2O2-hydroxylamine is a promising method for oxidative degradation of organic pollutants in the actual aqueous environmental systems.