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Research Papers

Treatment of Aqueous Solutions Containing Four Commercial Pesticides by Means of TiO2 Solar Photocatalysis

[+] Author and Article Information
A. García-Ripoll, A. Arques, R. Vicente, A. Domenech

Departamento de Ingeniería Textil y Papelera, Universidad Politécnica de Valencia, Campus de Alcoy, Plaza Ferrándiz y Carbonell, s.n., E-03801 Alcoy, Spain

A. M. Amat

Departamento de Ingeniería Textil y Papelera, Universidad Politécnica de Valencia, Campus de Alcoy, Plaza Ferrándiz y Carbonell, s.n., E-03801 Alcoy, Spainaamat@txp.upv.es

J. Sol. Energy Eng 130(4), 041011 (Sep 23, 2008) (5 pages) doi:10.1115/1.2969810 History: Received December 04, 2007; Revised December 18, 2007; Published September 23, 2008

Metasystox, Ultracid, Sevnol, and Laition are commercial pesticides, whose active ingredients are, respectively, oxydemethon-methyl, methidathion, carbaryl, and dimethoate. Laboratory scale experiments were carried out to treat solutions of the pure active ingredient and the commercial formulation employing a solar simulator as irradiation source. Degradation of the active ingredient followed in all cases a pseudo-first-order kinetic and rate constants, k, indicated that reaction was faster when the thiophosphate moiety was present. Additives existing in the commercial formulations resulted in an important decrease in the reaction rate, as k values were at least 50% lower than those obtained with the corresponding pure active principle (0.013min1 for Ultracid and 0.033min1 for methidathion, 0.011min1 for Laition and 0.026min1 for dimethoate, and 0.007min1 for Sevnol and 0.016min1 for carbaryl). Important increase in the surface tension was measured in all cases, indicating that the photocatalytic treatment is able to remove the surface active species present in the commercial formulation. Finally, assays based on the inhibition of the respiration of activated sludge indicated a decrease in the toxicity of all four commercial mixtures from initial values in the range 40–80% to achieve complete detoxification when the elimination of the active ingredient is reached.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Pseudo-first-order rate constants measured for the removal of four pesticides from aqueous solutions by means of photocatalysis with TiO2 in solar simulator. black bars: commercial formulations; gray bars: pure active ingredients

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Figure 2

Solar photocatalytic treatment of four commercial pesticides at pilot plant scale: (●) Metasystox, (◼) Ultracid, (▲) Sevnol, and (◆) Laition. The relative amount of each active ingredient is given as empty points while the remaining TOC is shown by the black points.

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Figure 3

Inhibition of the OUR of activated sludge produced by four solutions of commercial pesticides containing 50mg∕l of the active ingredient (black bars); data after 90% removal of the active ingredient are shown as gray bars

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Figure 4

Biodegradation determined according to the Zahn–Wellens test of aqueous solutions of four commercial pesticides before (black bars) and after a solar photocatalytic treatment (gray bars)

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Figure ch1

Chemical structures of oxydemethon-methyl (a), methidathion (b), carbaryl (c), and dimethoate (d)

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