Degradation of aqueous carbamazepine in ultrasonic/Fe0/H2O2 systems

This study investigated the suitability of carbamazepine (CBZ) oxidation by an improved Fenton's process. CBZ (42 mu M) is used as probe for non-halogenated pharmaceuticals. The experiments were performed at room temperature (21 +/- 2 degrees C) and different pHs (3, 5, 7 and 9). Powerful oxidative hydroxyl radicals for CBZ oxidation are produced by H2O2 (12.5-100 mM) and Fe-0 (0.44-3.57 mM) additives under low frequency ultrasonication (40 kHz). Results showed no CBZ oxidation in the presence of an center dot OH scavenger (MeOH), confirming the Fenton's nature of the process. Acid-washed Fe-0 feeding showed increased CBZ oxidative degradation up to 85%. Recycling experiments demonstrated also the ability of Fe-0 to maintain its capability of releasing Fe2+ into the media to promote center dot OH generation for CBZ degradation (>80% after 4 cycles). This was ascribed to the cracking effect on the surface of iron particles preventing thereby the formation of passive oxide. The process was also efficient in natural waters containing different species (e.g. Na+, Ca2+, Mg2+, Cl-, SO42-, HCO3-, NO3-, etc.). Intermediate oxidation products (by-products) were identified by LC/MS. However, by-products disappeared with longer experimental durations. The Fe-0/H2O2 ultrasonic process is a promising technique for oxidative removal of non-halogenated pharmaceuticals under mild conditions. (C) 2011 Elsevier B.V. All rights reserved.