Degradation of caffeine by conductive diamond electrochemical oxidation |
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Authors: | Chloe Indermuhle,Maria J. Martí n de Vidales,Cristina Sá ez,José Robles,Pablo Cañ izares,Juan F. Garcí a-Reyes,Antonio Molina-Dí az,Christos Comninellis,Manuel A. Rodrigo |
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Affiliation: | 1. Electrochemical Engineering Group, Chemical Engineering and Biochemistry Section, School of Basis Sciences, CHJ2 483, Station 6, CH-1015 Lausanne, Switzerland;2. Department of Chemical Engineering, Edificio Enrique Costa, Campus Universitario s/n, 13071 Ciudad Real, Spain;3. Analytical Chemistry Research Group, Department of Physical and Analytical Chemistry, University of Jaén, Campus Las Lagunillas, 23071 Jaén, Spain |
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Abstract: | The use of Conductive-Diamond Electrochemical Oxidation (CDEO) and Sonoelectrochemical Oxidation (CDSEO) has been evaluated for the removal of caffeine of wastewater. Effects of initial concentration, current density and supporting electrolyte on the process efficiency are assessed. Results show that caffeine is very efficiently removed with CDEO and that depletion of caffeine has two stages depending on its concentration. At low concentrations, opposite to what it is expected in a mass-transfer controlled process, the efficiency increases with current density very significantly, suggesting a very important role of mediated oxidation processes on the removal of caffeine. In addition, the removal of caffeine is faster than TOC, indicating the formation of reaction intermediates. The number and relative abundance of them depend on the operating conditions and supporting electrolyte used. In chloride media, removal of caffeine is faster and more efficiently, although the occurrence of more intermediates takes place. CDSEO does not increase the efficiency of caffeine removal, but it affects to the formation of intermediates. A detailed characterization of intermediates by liquid chromatography time-of-flight mass spectrometry seems to indicate that the degradation of caffeine by CDEO follows an oxidation pathway similar to mechanism proposed by other advanced oxidation processes. |
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Keywords: | Conductive-diamond Electrochemical oxidation Wastewater Caffeine |
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