Caffeine (C8H10N4O2) is a xanthine alkaloid compound, the most commonly used legal drug in the world. Approximately 3% of a person's caffeine intake is excreted in the urine; it has been detected in many surface streams and municipal wastewater treatment plants effluents. Therefore, it is necessary to develop reliable wastewater treatment processes for the removal of caffeine in wastewater. This study investigates the electrochemical oxidation of caffeine mainly on a boron-doped diamond (BDD) anode under galvanostatic electrolysis. The operating parameters (current density, initial concentration of caffeine, and sample matrix) of this electrolytic process were investigated. For comparison, a Pt or PbO2 planar electrode was also tested. According to cyclic voltammetric analysis, the oxidation of caffeine on BDD was found to be electrochemically irreversible. The electro-degradation of caffeine was a pseudo-first-order reaction in 0.1 M Na2SO4 or caffeine-spiked secondary wastewater treatment plant effluent solution. The degradation efficiency of caffeine increased with increasing current density but noticeably decreased as initial caffeine concentration increased. The BDD anode was superior to the PbO2 and Pt electrodes for caffeine electro-degradation. In addition to anode material, current density also influenced the mineralization current efficiency (MCE) of caffeine (or TOC). The complete removal of TOC could be achieved in this process. (The authors thank the National Science Council,Taiwan, for financially supporting this research under Contract Nos. NSC-102-2221-E-020-006-MY3 and NSC-102-2221-E-020-001-MY3.)

Anodic degradation of caffeine on a BDD electrode

248th National Meeting (2014)

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