CWPO intensification by induction heating using magnetite as catalyst

Abstract This work aims to evaluate the intensification of CWPO by the application of electro-magnetic induction heating (MIH) using an inexpensive magnetite mineral as catalyst. Experiments were carried out at pH0 = 5 using the persistent antibiotic sulfamethoxazole (SMX) as target pollutant (5 mgL−1) and the stoichiometric H2O2 dose (25 mgL−1). The effect of electro-magnetic field intensity (200–350 A, at a frequency of 223 kHz) and catalyst concentration (0.25–1.5 gL−1) on the kinetics as well as on the bulk solution temperature, were systematically evaluated. A clear increase on the oxidation rate of SMX was observed with increasing the electro-magnetic field intensity (2.1 × 10−2–6.9 × 10−2 min−1 by increasing the electro-magnetic field from 0 to 350 A), which was accompanied by a significant temperature rise (from 26 to 48 °C). Remarkably, even operating under the same bulk solution temperature, the MIH-CWPO process led to oxidation rates significantly faster than the achieved with the non-MIH assisted CWPO system (e.g. up to three times higher at 350 A, being both operated at 56 °C). The effect of temperature on the process kinetics was finally evaluated, obtaining an activation energy value of 41 kJmol−1. On the basis of these results, the actual temperature of the solid particles in the MIH-CWPO system was accordingly estimated. The localized heating of these particles led to temperatures much higher than those of the surrounding liquid phase (e.g. 79 vs. 56 °C at 350 A), which was the reason behind the process kinetics enhancement.