Electrochemical synthesis of peroxomonophosphate using boron-doped diamond anodes |
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Authors: | E Weiss C Sáez K Groenen-Serrano P Cañizares A Savall M A Rodrigo |
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Affiliation: | (1) Laboratoire de Génie Chimique, CNRS, Université Paul Sabatier, 31062 Toulouse Cedex 9, France;(2) Department of Chemical Engineering, Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Campus Universitario s/n, 13071 Ciudad Real, Spain |
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Abstract: | A new method for the synthesis of peroxomonophosphate, based on the use of boron-doped diamond electrodes, is described. The
amount of oxidant electrogenerated depends on the characteristics of the supporting media (pH and solute concentration) and
on the operating conditions (temperature and current density). Results show that the pH, between values of 1 and 5, does not
influence either the electrosynthesis of peroxomonophosphate or the chemical stability of the oxidant generated. Conversely,
low temperatures are required during the electrosynthesis process to minimize the thermal decomposition of peroxomonophosphate
and to guarantee significant oxidant concentration. In addition, a marked influence of both the current density and the initial
substrate is observed. This observation can be explained in terms of the contribution of hydroxyl radicals in the oxidation
mechanisms that occur on diamond surfaces. In the assays carried out below the water oxidation potential, the generation of
hydroxyl radicals did not take place. In these cases, peroxomonophosphate generation occurs through a direct electron transfer
and, therefore, at these low current densities lower concentrations are obtained. On the other hand, at higher potentials
both direct and hydroxyl radical-mediated mechanisms contribute to the oxidant generation and the process is more efficient.
In the same way, the contribution of hydroxyl radicals may also help to explain the significant influence of the substrate
concentration. Thus, the coexistence of both phosphate and hydroxyl radicals is required to ensure the generation of significant
amounts of peroxomonophosphoric acid. |
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Keywords: | Conductive-diamond Electrosynthesis Electrolysis Oxidation |
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