title: Degradation of caffeine by conductive diamond electrochemical oxidation.
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.
authors.affiliation: Electrochemical Engineering Group, Chemical Engineering and Biochemistry Section, School of Basis Sciences, CHJ2 483, Station 6, CH-1015 Lausanne, Switzerland.
authors.forename: Chloe
authors.initials: C
authors.lastname: Indermuhle
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Martín de Vidales
authors.forename: Cristina
authors.initials: C
authors.lastname: Sáez
authors.forename: José
authors.initials: J
authors.lastname: Robles
authors.forename: Pablo
authors.initials: P
authors.lastname: Cañizares
authors.forename: Juan F
authors.initials: JF
authors.lastname: García-Reyes
authors.forename: Antonio
authors.initials: A
authors.lastname: Molina-Díaz
authors.forename: Christos
authors.initials: C
authors.lastname: Comninellis
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Rodrigo
mesh_terms: D002110:Caffeine / Q000032:analysis / Q000737:chemistry*; D018130:Diamond / Q000737:chemistry; D004563:Electrochemistry; D008956:Models, Chemical; D010084:Oxidation-Reduction; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D014874:Water Pollutants, Chemical; D002110:Caffeine; D018130:Diamond
keywords: Caffeine; Conductive-diamond; Electrochemical oxidation; Wastewater