Electrochemical mineralization of sodium dodecylbenzenesulfonate at boron doped diamond anodes |
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Authors: | Elsa Weiss Karine Groenen-Serrano André Savall |
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Affiliation: | (1) Laboratoire de Génie Chimique UMR 5503 CNRS, Université Paul Sabatier, Toulouse Cedex 9, 31062, France |
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Abstract: | Results are reported of the electrochemical oxidation of sodium dodecylbenzenesulfonate (SDBS), a common surfactant, at boron-doped
diamond anodes. The measured critical micelle concentration (CMC) for SDBS in water at 24 °C was almost 150 mg dm−3, but this decreased to almost 30 mg dm−3 in 0.1 M sodium sulfate. Cyclic voltammetry of a boron doped diamond (BDD) electrode in aqueous SDBS solutions exhibited
oxidation current densities at very positive potentials; however, solutions of monomers at concentrations <CMC gave rise to
higher current densities than in higher concentration solutions that formed micelles. Galvanostatic electrolyses, with samples
analyzed for Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD), were performed in an electrolytic flow cell without
separator, operating in batch recycle mode, using solutions containing SDBS at initial concentrations of 25 and 250 ppm. SDBS
in basic media (pH = 12) exhibited lower TOC removal rates than in acidic or neutral solutions, due to concurrent oxidation
of dissolved carbonates at potentials less positive than required for water oxidation, as evident in cyclic voltammograms.
Decreasing the electrolyte]/surfactant] ratio from 200 to 10 increased TOC removal rates. For solutions containing monomers,
TOC removal rates also increased with flow rate in the second part of the electrolysis, corresponding to reaction of smaller,
fragmented organic compounds. When COD removal from a solution containing SDBS micelles was mass transport controlled, current
efficiencies were constant at ca. 50%, due to dimerisation of hydroxyl radical to H2O2 and its oxidation to dioxygen. |
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Keywords: | Electrooxidation Boron doped diamond Dodecylbenzenesulfonate Critical micelle concentration |
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