Ultrasound, electrochemistry and water treatment

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					              Ultrasound, electrochemistry and water treatment
                                 L Paniwnyk
      Sonochemistry Centre, Faculty of Health and Life Sciences, Coventry University,
                         Priory Street, Coventry CV1 5FB, U.K.

In many areas of the world it is often necessary to produce drinking water from polluted
surface waters and much research has been focussed on the reduction of the concentration
of contaminants, particularly pesticides such as chlorinated phenols [1], to a level which is
safe for the consumer [2]. In this study we report on the overall degradation of some
chlorophenol compounds using a carbon-based composite electrode, specifically designed for
this purpose using activated carbon prepared from olive stones, normally considered a waste
material [3]. A direct comparison between the rate of decomposition of the chlorophenols
using the prepared electrode with that obtained by using a carbon rod electrode is discussed.
The results obtained from this preliminary study [4] informed the development of a novel
combination process that of an Electro-Fenton´s system that coupled with sonication that
would effectively merge the adsorption, diffusion and the destruction of chlorinated phenols
Chlorinated phenols are known to be destroyed by highly oxidising hydroxyl radicals OHº [6]
which can be produced by the reaction between hydrogen peroxide (H2O2) and iron (II),
known as Fenton’s reagent [4] as described by Walling and Goosen [7].

Fe2+ + H2O2     Fe3+ +OHº + OH-

Ultrasound coupled with electrochemistry has also recently been used to produce hydroxyl
radicals and it has been shown that the Fenton’s reagent can be sonoelectrochemically
produced in the bulk of the solution [8]. This system is frequently named the Electro-Fenton.
Results indicate that the system is effective in the treatment of aqueous samples
contaminated with chlorophenols. However the removal rate depends on several parameters
such as the concentration of chlorophenol, the composition of the electrolyte solution,
(including pH), applied potential and the electrode “contact area”.

1. Alloway, B. J. and Ayres, D.C.Chemical principles of Environmental Pollution,1st
Edition,Chapman and Hall, London, (1993)
2. Guido Achilli , Gian Piero Cellerino, Gianvico Melzi d'Eril, Sue Bird.
“Simultaneous determination of 27 phenols and herbicides in water by high-performance
liquid chromatography with multi-electrode electrochemical detection,” Journal of
Chromatography A, 697, 357-362, (1995)
3. A.H.El-sheikh, Alan P. Newman, Hafid K.Al-Daffaee, Suki Phull and Neil Cresswell –
Characterization of Activated Carbon Prepared From a Single Cultivar of Jordanian Olive
stones by Chemical and Physicochemical Techniques /Journal of Analytical Applied Pyrolysis
00, 1-16, (2003)
4. Katteia D. Correia, MSc Thesis, Coventry University (2005)
5. Elena Madrid, MSc Thesis, Coventry University (2007)
6. Serge Chiron, Amadeo Fernández-Alba, Antonio Rodriguez and Eloy García-Calvo
“Pesticide chemical oxidation: State-of-the-Art” Wat. Res. Vol. 34, No. 2, pp. 366±377, (2000)
7. Walling C, Goosen A. Mechanism of ferrous ion catalyzed decomposition of hydrogen
peroxide. Effect of organic substrates.” J Am Chem Soc, 95(9):2987–91, (1973).
8. A. Ventura, G. Jacquet, A. Bermond, V. Camel, “Electrochemical generation of the
Fenton’s reagent: application to atrazine degradation”, Water Research 36, 3517–3522,