Technical Note Ferrate(VI) oxidation of propranolol: Kinetics and products George A.K. Anquandah a , Virender K. Sharma a,⇑ , Venkata R. Panditi b , Piero R. Gardinali b , Hyunook Kim c , Mehmet A. Oturan d a Department of Chemistry and Center of Ferrate Excellence, Florida Institute of Technology, Melbourne, FL 32901, USA b Department of Chemistry and Biochemistry, Florida International University, 3000 NE 151st St., North Miami, FL 33181, USA c The University of Seoul, Department of Environmental Engineering, 90 Jeonnong-dong Dongdaemun-gu, Seoul 130-743, Republic of Korea d Université Paris-Est, Laboratoire Géomatériaux et Environnement (LGE), EA 4508, UPEMLV 77454 Marne-la-Vallee, France highlights " Reaction kinetics of Fe(VI) and propranolol is similar to secondary amines. " Complete transformation of propranolol by Fe(VI) in water. " Opening of aromatic ring of propranolol by Fe(VI). " Hydroxylation of amine moiety of propranolol by Fe(VI). article info Article history: Received 5 October 2012 Received in revised form 30 November 2012 Accepted 1 December 2012 Available online 7 January 2013 Keywords: Ferrate Beta blockers Kinetics Removal Oxidized products abstract The oxidation of propranolol (PPL), a b-blocker by ferrate(VI) (Fe(VI)) was studied by performing kinetics, stoichiometry, and analysis of the reaction products. The rate law for the oxidation of PPL by Fe(VI) was first-order with respect to each reactant. The dependence of second-order rate constants of the reaction of Fe(VI) and PPL on pH was explained using acid–base equilibrium of Fe(VI) and PPL. The required molar stoichiometry for the complete removal of PPL was determined to be 6:1 ([Fe(VI)]:[PPL]). The identified products using liquid chromatography–tandem mass spectrometry were oxidized product (OP)-292, OP- 308, and OP-282. The formed OPs could possibly compete with the parent molecule to react with Fe(VI) and thus resulted in a non-linear relationship between degradation of PPL and the added amount of Fe(VI). Rate and removal studies indicate the Fe(VI) is able to oxidize PPL and hence can also oxidize other b-blockers, e.g., atenolol and metoprolol. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Emerging pollutants such as pharmaceuticals in the aquatic environment are of increasing concern to the ecosystem sustain- ability. Sources of pharmaceuticals in the surface water include industry, hospital, and domestic wastewaters containing unused or human excreted drugs (Deblonde et al., 2011). b-Blockers (b- andrenergic receptor antagonists) are among the important class of pharmaceuticals, which have been found at low concentrations up to lgL 1 in surface waters (Benotti et al., 2009; Martínez Bueno et al., 2012). The levels of b-blockers are expected to increase with the increase of the world population and its age and high concen- trations might be ecotoxicologically harmful. Some studies have shown effect of b-blockers on the aquatic organisms (Huggett et al., 2002; Küster et al., 2010). Mixtures of b-blockers have addi- tive effects on the organisms and thus even low concentrations may contribute to the toxicity. A b-blocker, propranolol (1-(1- methylethylamino)-3-(1-naphthyloxy)propan-2-ol, PPL), which has significantly higher toxicity to aquatic organisms compared to other b-blockers, atenolol and metoprolol (Fent et al., 2006), is the focus of the present study. Beta-blockers are not completely removed by conventional treat- ment processes in a wastewater treatment plant (WWTP) due to their recalcitrant nature (Gabet-Giraud et al., 2010). For example, PPL was removed about 20% by WWTP (Gros et al., 2010). On the other hand, no evidence for biotransformation or biologically med- iated removal of PPL was observed while a very slow abiotic process removing 20% of PPL over 79 d (Barbieria et al., 2012). Alternate treatment methods such as advanced oxidation processes have been tested to remove b-blockers in water (Benitez et al., 2011; Isarain- Chávez et al., 2011; Chen et al., 2012; Köhler et al., 2012; Sirés and Brillas, 2012). Treatment of PPL has been studied by photo-catalytic oxidation, ozonation, UV/O 3 , UV/H 2 O 2 , and O 3 /H 2 O 2 , and electro- chemically (Andreozzi et al., 2004; Benner et al., 2008; Piram et al., 2008; Sharma, 2008; Benner and Ternes, 2009a,b; Kim et al., 2009; 0045-6535/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.12.001 ⇑ Corresponding author. Tel.: +1 321 674 7310; fax: +1 321 674 8951. E-mail address: vsharma@fit.edu (V.K. Sharma). Chemosphere 91 (2013) 105–109 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere