Electrochemical incineration of benzoquinone in aqueous media using a quaternary metal oxide electrode in the absence of a soluble supporting electrolyte

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Abstract

Electrochemical incineration of p-benzoquinone was evaluated as a model for the mineralization of carbon in toxic aromatic compounds. A Ti or Pt anode was coated with a film of the oxides of Ti, Ru, Sn and Sb. This quaternary metal oxide film was stable; elemental analysis of the electrolysed solution indicated the concentration of these metal ions to be 3μg L−1 or less. The anode showed good reactivity for the electrochemical incineration of benzoquinone. The use of a dissolved salt matrix as the so-called ‘supporting electrolyte’ was eliminated in favor of a solid-state electrolyte sandwiched between the anode and cathode. This substitution permitted the electrolysis solution to be analysed by electrospray mass spectrometry (ESMS); however, as a consequence, electrolysis periods were excessively long. Total organic carbon (TOC) and chemical oxygen demand (COD) decreased to 1–2 mgL−1 after 64h of electrolysis. The solution pH changed from 5 to 4. Phenolic and carboxylic acid intermediate products such as hydroquinone, maleic acid, fumaric acid, succinic acid, malonic acid, acetic acid and formic acids were identified and quantified using solid phase microextraction with gas chromatography with mass spectrometric detection (GCMS) or liquid chromatography (LC) with conductivity detection, absorbance detection, or electrosprary mass spectrometry (ESMS). Less than 1% of the carbon in benzoquinone was converted to acetone and acetaldehyde.

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