Electrochemical degradation of the β-blocker metoprolol by Ti/Ru0.7Ir0.3O2 and Ti/SnO2-Sb electrodes

Abstract

BioassaysHalogenated by-product Micropollutant a b s t r a c t Electrochemical oxidation has been proposed for the elimination of pesticides, pharmaceuticals and other organic micropollutants from complex waste streams. However, the detrimental effect of halide ion mediators and the generation of halogenated by-products in this process have largely been neglected thus far. In this study, we investigated the electrochemical oxidation pathways of the b-blocker metoprolol in reverse osmosis concentrate (ROC) from a water reclamation plant using titanium anodes coated with Ti/SnO 2 -Sb exhibited higher oxidizing power for the same applied specific electrical charge, the generation of large fractions of chloro-, chloro-bromo-and bromo derivatives was observed for both electrode coatings. However, degradation rates of metoprolol and its degradation products were generally higher for the Ti/SnO 2 -Sb anode. Chemical analyses of metoprolol and its by-products were complemented with bioanalytical tools in order to investigate their toxicity relative to the parent compound. Results of the bioluminescence inhibition test with Vibrio fischeri and the combined algae test with Pseudokirchneriella subcapitata indicated a substantial increase in non-specific toxicity of the reaction mixture due to the formed halogenated by-products, while the specific toxicity (inhibition of photosynthesis) remained unchanged. ª 2011 Elsevier Ltd. All rights reserved. IntroductionThe unique ability of electrochemical processes to oxidize and/ or reduce organic compounds at controlled electrode potentials and using only electrons as reagents represents a great advantage over existing advanced oxidation processes (AOPs). Due to the generation of a variety of reactive oxygen species (ROS) at the anode (e.g. OH -, H 2 O 2 , O 2 , O 3 ), electrochemical oxidation is considered to be versatile and capable of oxidizing persistent organic micropollutants, nitrogen species and microorganisms (Comninellis et al., 2010). In recent years, there has been an increasing interest in applying electrochemical oxidation for the treatment of refractory waste streams such as landfill leachate and reverse osmosis concentrate (ROC) from water treatment processes (Anglada et al., 2009;Van Hege et al., 2004;Dialynas et al., 2008;Perez et al., 2010). Due to the high concentrations of organic contaminants, disposal of these streams represents a major problem as they require an on-site treatment. A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s w a t e r r e s e a r c h 4 5 ( 2 0 1 1 ) 3 2 0 5 e3 2 1 40043-1354/$ e see front matter ª

Electrochemical removal of pharmaceuticals from water streams: Reactivity elucidation by mass spectrometry

“…Please cite this article in press as: Enric Brillas, Ignasi Sirés, Electrochemical removal of pharmaceuticals from water streams: Reactivity elucidation by mass spectrometry, Trends in Analytical Chemistry (2015), doi: 10.1016/j.trac.2015.01.013 compared to those determined for EO in sulfate medium, although at least it accelerates the decay of the initial pharmaceutical and its cyclic/aromatic products, as found for β-blocker metoprolol [13,15].…”

“…Several pharmaceutical solutions have been degraded by EO using active anodes {e.g. Pt [11] and Ti/RuO2-IrO2 [12,13]}. In contrast, a non-active anode favors the formation of physisorbed M( • OH) that leads to the electrochemical mineralization of organics.…”

“…In contrast, a non-active anode favors the formation of physisorbed M( • OH) that leads to the electrochemical mineralization of organics. By using this approach, the treatment of synthetic and real drug solutions by EO with SnO2 doped with Sb [13,14] and boron-doped diamond (BDD) [11,[15][16][17] has been reported. BDD thin-film electrodes deposited onto p-Si, Nb or Ti show the highest overpotential for O2 evolution and the low adsorption enthalpy of BDD-• OH allows the production of larger amounts of reactive BDD( • OH) compared to other anodes, thereby yielding the most effective mineralization of organic pollutants.…”

“…A very different behavior is usually found when the treated effluent contains chloride ions, as in the case of real wastewater [1,7,12,13,15,17], since active chlorine species (e.g. Cl2, HClO and/ or ClO − ) are generated from Cl − oxidation via reactions (2)-(5) as follows: ( )…”

Active anti-fouling and defouling of membranes using electrochemical methods

“…The oxidizing power of an anode is determined by the anode overpotential for the oxygen evolution reaction and the adsorption enthalpy of the OH radicals created [104,105]. By-products result from incomplete oxidation due to the selectivity of the electrode material (direct) or the intermediate (indirect Anodes that can combust organics include graphite felt with palladium nanoparticles [110], and mixed metal oxides [111,112] including Ti/SnO2-Sb and Ti/PbO2 [106].…”