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Sonolytic, Photolytic, and Photocatalytic Decomposition of Atrazine in the Presence of Polyoxometalates A. HISKIA,† M. ECKE,‡ A. TROUPIS,† A . K O K O R A K I S , ‡ H . H E N N I G , * ,‡ A N D E . P A P A C O N S T A N T I N O U * ,† Institute of Physical Chemistry, NCSR Demokritos, 153-10 Athens, Greece, and Universitaet Leipzig, Institut fu ¨ r Anorganische Chemie, Johannisallee 29, D-041003 Leipzig, Germany
Aqueous solutions of atrazine [2-chloro-4-(isopropylamino)-6-(ethylamino)-s-triazine] (CIET) decompose upon illumination with a low-pressure Hg-arc lamp (254 nm). However, no decomposition takes place with λ > 300 nm. On the other hand, addition of polyoxometalates (POM), PW12O403- or SiW12O404-, into a solution of atrazine photodecomposes the substrate within a few minutes (cutoff flter 320 nm). Ultrasound (US) treatment also decomposes aqueous solutions of atrazine within a few minutes. Both methods, sonolysis and photolysis with POM, give common intermediates, namely, 2-hydroxy-4(isopropylamino)-6-(ethylamino)-s-triazine (OIET), 2-chloro4-(isopropylamino)-6-amino-s-triazine (CIAT), 2-chloro-4amino-6-(ethylamino)-s-triazine (CAET), 2-hydroxy-4,6diamino-s-triazine (OAAT), and 2-hydroxy-4-hydroxy-6-aminos-triazine (OOAT) among others. The final products for both methods, US and photolysis with POM, were cyanuric acid (OOOT), NO3-, Cl-, CO2, and H2O. OOOT showed no signs of decomposition by sonication and/or photolysis with POM. It also resisted degradation upon photolysis with plain UV light (254 nm). However, it has been reported to decompose upon photolysis with λ > 200 nm. Combination of US and photolysis with POM produces only a cumulative effect.
Introduction s-Triazine herbicides are extensively used in the control of various crop cultures (1, 2) and of weed in nonagricultural areas (3). Their persistence and wide application have resulted in serious contamination not only in agricultural sites, but also of surface, groundwater, and drinking water supplies as well (4, 5). Atrazine is most widely used among s-triazine herbicides. Atrazine is also quite persistent in the environment and has become, therefore, a serious environmental concern. The EU maximum acceptable concentration of individual pesticide and toxic transformation products in drinking water ought to be below 0.1 ppb, whereas the maximum allowed concentration of all pesticides is 0.5 ppb (6). Atrazine degradation has been studied by various biological (7-9) and Advanced Oxidation Processes (AOP) that † ‡
Institute of Physical Chemistry, NCSR Demokritos. Universitaet Leipzig, Institut fu ¨ r Anorganische Chemie.
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include UV and H2O2 (10), Fenton reagent (11), photoassisted Fenton reagent (12, 13), ozonation (14), and TiO2-supported UV photolysis (15-19), and preliminarily by sonolysis as well (20). There is confusion in the literature on the effect of OH radicals on the destruction of atrazine. Thus, the formation of the dechlorination product 2-hydroxyatrazine (OIET) (see Table 1 for nomeclature of atrazine and its degradation products usually encountered in the literature) is attributed to hydroxy radicals whereas in the nonphotolytic OH radical system OIET was not observed (21). Nevertheless, for the AOP that act, mainly, through formation of OH radicals, most authors seem to agree that decomposition of atrazine involves dealkylation, deamination, and to a lesser extent dechlorination, whereas, with a few exceptions, cyanuric acid (OOOT) was reported to be the final degradation product. POM are metal-oxygen cluster anions, produced by acid condensation of mainly MoO42- and/or WO42- (22). Absorptions that characterize POM are known to be devided, roughly, into three main categories: M-M CT bands, responsible for the coloration (mainly blue) of the reduced POM; d-d transitions; and O f M CT bands. Of these bands, the O f M CT band is photoactive and can be presented pictorially as
where -WdO is a metal-oxygen bond in POM. We have demonstrated that photocatalytic processes in the presence of polyoxometalates (POM) are comparable with AOP treatment in that upon excitation of the O f M CT state (by using near-visible and UV light), these anions become powerful oxidizing reagents able to mineralize a great variety of organic pollutants such as phenol, p-cresol (23), chlorophenols (24-27), chloroacetic acids (28), and organochlorine pesticides (29). On the other hand, sonolysis is a rather new procedure that has been successfully used in the mineralization of organic pollutants (30). Ultrasound leads to pressure changes in liquids. Periodical compression and expansion occurs within the medium depending on the frequency. This gives rise to the generation of cavitations. Further energy input leads to a collapse of these cavitations. This is connected with an extreme temperature and pressure increase of some 5000 K and 500 kPa. Because the compression occurs almost adiabatically, nearly no heat exchange with the surroundings takes place. The temperature within the short-lived cavitations is sufficiently enough to split water into H and OH radicals. The latter radicals are able to destroy any organic wastes due to their high oxidation potential. Further, hydrogen peroxide forms due to the recombination of OH radicals. Hydrogen peroxide is available, therefore, as additional oxidant. Another aspect is due to the diffusion of any organic compound into the cavitations filled with supercritical and therefore lipophilic water vapor. This leads to pyrolysis of these compounds at the hot surfaces of the cavitations (31). In this paper, we report on the decomposition of atrazine by sonolysis with acoustic waves of 850 kHz, photocatalytic processes using two characteristic POM (PW12O403- and SiW12O404-, respectively), and a combination of sono- and photocatalytic, using POM. The effect of direct photolysis of atrazine with various wavelengths is also reported. 10.1021/es000212w CCC: $20.00
2001 American Chemical Society Published on Web 04/26/2001
TABLE 1. Chemical Names, Trivial Names, and Nomenclature by Cook and Hutter for Atrazine and Its Metabolites Identified during Photocatalyic Treatment with POM or Sonochemical Treatment chemical name
trivial names
2-chloro-4-(isopropylamino)-6-(ethylamino)-s-triazine 2-chloro-4-amino-6-(ethylamino)-s-triazine 2-chloro-4-(isopropylamino)-6-amino-s-triazine 2-chloro-4,6-diamino-s-triazine 2-hydroxy-4-(isopropylamino)-6-(ethylamino)-s-triazine 2-hydroxy-4,6-diamino-s-triazine 2-hydroxy-4-hydroxy-6-amino-s-triazine 2,4,6-trihydroxy-s-triazine
atrazine DIA, deisopropylatrazine DEA, deethylatrazine
Polyoxometalates (POM) are a new category of photocatalysts. In contrast with the widely studied TiO2 (more than 1500 papers), the photocatalytic action of POM is still under investigation. The alternatives offered by POM photocatalysis for the decontamination of water from organic pollutants have been recently presented (24, 25, 26, 28). As far as we are aware of, no results have been reported on the photodegradation of atrazine using POM as catalysts. Recently, Giannotti’s group has reported on the photodegradation of atrazine by two catalysts, TiO2 and W10O324- (32, 33), though no detection of the final products was given. Their results will be discussed in view of our findings. In this study, further information is given concerning the determination, for the first time, of the final products of low toxicity, giving the opportunity for the environmental assessment of the process. In addition, the work about sonolysis of atrazine is very limited, involving only one paper (20) with little information concerning the degradation products and the mechanism of the process.
Experimental Section H3PW12O40 and K4SiW12O40 were prepared according to the literature (34). PW12O403- is stable at pH ca. 1, whereas SiW12O404- is stable up to pH ca. 5.5. Since the membranes of the sonolysis apparatus were sensitive to lower pH, preferably SiW12O404- was used. It is noted that these two POM have similar photochemical behavior except that photodegradation rates with PW12O403- appear to be about 2-3-fold faster than with SiW12O404-. Atrazine (CIET), 2-chloro-4-(isopropylamino)-6-aminos-triazine (CIAT), 2-chloro-4-amino-6-(ethylamino)-s-triazine (CAET), 2-chloro-4,6-diamino-s-triazine, 2-hydroxy-s-triazine (OIET), and 2-hydroxy-4,6-diamino-s-triazine (OAAT) were obtained from Chem Service, with a purity of 98, 95, 97, 95, and 99%, respectively. 2-Hydroxy-4-hydroxy-6-amino-striazine (OOAT) was kindly provided by Prof. E. Pelizzetti’s group. Cyanuric acid (OOOT) was a product of Merck, analytical grade. Acetonitrile was HPLC grade. Ultrapure water was obtained from a compact apparatus from Barnstead. Extra pure argon and dioxygen were used for deaeration and oxygenation of solutions. A typical experiment was as follows: Oxygenated aqueous atrazine solution (7 × 10-5 M; 4 mL) containing catalyst SiW12O404- (7 × 10-4 M) was added to a spectrophotometer cell (1 cm path length) which was covered with a cerum cap. The pH was maintained at 5.0. Photolysis was performed with an Oriel 1000 W Xe arc lamp equipped with a cool water circulating filter to absorb the near-IR radiation and a 320 nm cutoff filter to avoid direct photolysis of substrates. The degree of reduction of POM in photolyzed deaerated solutions was estimated UV/Vis-spectroscopically by means of a HITACHI U-2000 spectrophotometer. The decay of the substrate and the production of intermediates were monitored by HPLC-UV consisting of a Waters model 600E pump associated with a Waters model 600 gradient controller, a
HA, hydroxyatrazine ammeline ammelide CA, cyanuric acid
nomeclature by Cook and Hutter CIET CAET CIAT CAAT OIET OAAT OOAT OOOT
Rheodyne model 7725i sample injector equipped with a 20 µL sample loop, a reversed-phase (RP) C18 analytical column by Phase Sep (25 cm × 4.6 mm i.d., 5 µm), and a Waters model 486 tunable absorbance detector controlled by Millenium (Waters) software. The mobile phase gradient program performed for the determination of atrazine and intermediate photolysis and/or sonolysis products was the following: for acetonitrile-water (20:80, v/v), in the isocratic mode over 5 min to 70% acetonitrile over 30 min and back to the initial condition in 1 min, at a flow rate of 1.5 mL/min. The wavelength used was 225 nm for the determination of atrazine, CIAT, CAET, and CAAT or 215 nm for OAAT, OOAT, and OOOT. For OIET detection, the detector was adjusted at 240 nm. Chloride and nitrate were analyzed by a Waters apparatus equipped with an IC-PakA HR (75 × 4.6 mm, 6 µm) column and a Waters model 430 conductivity detector. The eluent mixture was borate/gluconate concentrate-1-butanolacetonitrile-H2O (2:2:12:84; v/v) at pH 8.5, in the isocratic mode, at a flow rate of 1 mL/min. The borate/gluconate concentrate solution consisted of 16 g of sodium gluconate, 18 g of boric acid, 25 g of sodium tetraborate, and 250 mL of glycerin in 1 L of aqueous solution. Sonolysis was performed by means of a concave transducer membrane with a silver mirror construction, able to convert ca. 60% of electrical energy to ultrasound. The system was driven by a 850 kHz, 120 W electric power supply (Meinhardt Ultraschalltechnik, Leipzig). Of the corresponding solution, 45 mL was treated sonolytically in a special reactor consisting of a quartz tube of 108 mm length and a diameter of 25 mm. The quartz tube was equipped with a Teflon bottom (25 mm diameter) performable for ultrasound and immersed in an ultrasonic bath (330 mL saturated NaNO3) equipped with a double-glass cylinder and cooling jackets. Simultaneous UV irradiation was performed by means of an Oriel 1000 W Xe arc lamp and a 320 nm cutoff filter.
Results and Discussion Table 1 provides the chemical formulas of atrazine as well as the various intermediates formed in degradation processes together with the chemical name, the trivial names, and the nomeclature used by Cook and Hutter (35). It is reminded that in this nomeclature the following symbols are used: A, amino; C, chloro; E, ethylamino; I, isopropylamino; O, hydroxy; and T, s-triazine ring. Trivial names or the nomeclature of Cook and Hutter will be used. Sonochemical Decomposition of Atrazine. Sonolysis is a process in which acoustic waves of high frequency are transmitted through a solution (36). This results in the formation and collapse of small gas bubbles in which, for aqueous media, temperatures of about 5000 °C and hundreds of atmospheres pressure develop, as mentioned earlier. Under these conditions, water breaks up to OH and H radicals. The process is analogous to irradiating aqueous solutions with 60Co γ-radiation, but no solvated electrons are formed sonolytically (37). VOL. 35, NO. 11, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Sonolytic degradation of atrazine in the absence (9) or presence (0) of SiW12O404- (7.0 × 10-4 M). Initial concentration of atrazine, 7.0 × 10 -5 M (15 ppm), pH 5.0 (HClO4), 45 mL solution. Ultrasound frequency, 850 kHz.
FIGURE 2. Formation and decay of several intermediates at the early stages of atrazine sonodecomposition. Experimental conditions as reported in Figure 1 in the absence of POM. Highly oxidizing OH radicals, whose presence has been detected by spin trapping techniques (38, 39), are responsible for the degradation of a variety of organic pollutants. An advantage of this process is that, unlike light, ultrasound (US) can be transmitted through opaque systems. Thus, aqueous solutions of atrazine decomposed within ca. 60 min when subjected to 850 kHz (120 W electrical power) ultrasonic irradiation, as shown in Figure 1. Figure 1 also shows that addition of SiW12O404- to a solution of atrazine that underwent sonolytic treatment had no effect on the decomposition of substrate. The catalyst remained intact throughout the experiment. Several intemediates developed and decayed within the first 1-2 h of sonolysis, i.e., HA (OIET), DIA (CAET), and DEA (CIAT) (Figure 2), as well as several other intermediates identified only by their retention time (Figure 3). Another group of intermediates forms and decays after 30-50 h of sonolysis, containing, among others, CAAT and OOAT (see Figure 4). Cyanuric acid (OOOT) was found to be the final product in atrazine decomposition by sonolysis (Figure 4), together with the Cl- ions shown in Figure 5. Although degradation of atrazine was complete within 60 min by sonication, leading to OOOT (see Figure 4), OOOT was not affected by sonication for 3 h. Only an increase of the concentration of H2O2 could be detected in this period of time. Nitrate, which is, most likely, the final product due to the decomposition of side chain nitrogens of atrazine, could not be verified. High concentrations of nitrate developed during 2360
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FIGURE 3. Formation and decay of intermediates as identified by their retention time upon sonolysis of atrazine. Conditions as in Figure 2.
FIGURE 4. Formation and decay of CAAT and OOAT during sonolysis of atrazine and evolution of OOOT, the final organic product. Experimental conditions as reported in Figure 2.
FIGURE 5. Evolution of chloride ions upon sonolysis during sonochemical decomposition of atrazine. Conditions as in Figure 2. sonolysis due to N2 fixations by OH radicals and the high temperature of the cavities (40). Photocatalytic Decomposition of Atrazine in the Presence of SiW12O404-. It has been established that illumination of POM in the range of the O f M CT band, i.e., below 400 nm, enhances their oxidizing ability, by more than ca. 3.0 eV electronic excitation, and makes them powerful oxidizing reagents which are able to oxidize a great variety of organic substrates (23-25, 28, 29) either directly or indirectly through formation of OH radicals (41) according to the following
FIGURE 6. Direct photolysis of atrazine (λ ) 254 nm, λ > 300 nm, or λ > 350 nm). general reactions (23, 37):
FIGURE 7. Gradual development of the characteristic blue color of the one-electron-reduced 12-tungstosilicate, SiW12O405-, upon photolysis (λ > 320 nm) of a deaerated aqueous solution (pH 5.0, HClO4) of SiW12O404- (7 × 10-4 M) in the presence of atrazine (7 × 10-5M). Time (in minutes) is indicated on the spectra.
Excitation: hv
POM 98 POM*
(1)
Direct reaction of the excited POM with S: POM* + S f POM(e-) + Sox
(2)
Indirect reaction of the excited POM with S via formation of OH radicals: POM* + H2O f POM(e-) + OH + H+
(3)
Reaction of OH radicals with S: OH + S f oxidation products
(4)
Reoxidation (regeneration) of catalyst: 2POM(e-) + (1/2)O2 + 2H+ f POM + H2O (42) (5) where S ) organic pollutant. In the case of atrazine, the above reactions involve dealkylation, deamination, and to a lesser extent dechlorination, giving cyanuric acid (OOOT) as the final degradation product, together with chloride and nitrate, as mentioned earlier. In analogy with TiO2, formation of OH radicals is claimed during photolysis of POM. The formation of OH radicals, in the photocatalytic processes with POM, has been suggested by (a) identification of hydroxylation intermediates (23-25, 28), (b) EPR with OH radical trapping techniques (43), and (c) the ability of excited POM to oxidize hydroxyl ions OHand/or water. Photolysis with 254 nm light resulted in decomposition of atrazine within 1 h, whereas irradiation of substrates by using cutoff filters of 350 and 300 nm had no effect, as shown in Figure 6. When SiW12O404- was added to an oxygenated aqueous solution of atrazine, irradiation by means of a cutoff filter (320 nm) resulted in photodecomposition of the substrate within ca. 60 min (Figure 8). The process could be followed in the absence and presence of dioxygen by observing the development of the blue color of the reduced POM (Figure 7) (implying the concomitant oxidation of atrazine) or the decomposition of atrazine by means of HPLC (Figure 8), respectively. Several intermediates form and decay within the first hours of photodegradation of oxygenated aqueous solutions of atrazine in the presence of POM, namely, CAET, CIAT, and OIET (Figure 9) as well as three more identified by their retention time, as shown in Figure 10. CAAT and ammeline
FIGURE 8. Photocatalytic degradation of atrazine in the presence of SiW12O404- (7.0 × 10-4 M). Initial concentration of substrate, 7.0 × 10-5 M (15 ppm), pH 5.0, λ > 320 nm; 4 mL of oxygenated solution.
FIGURE 9. Evolution and decay of the intermediates CAET, CIAT, and OIET during the photocatalytic degradation of atrazine. Experimental conditions as reported in Figure 8. (OAAT) appear and decay within the first 20 h (Figure 11). The formation of cyanuric acid (OOOT) begins after 10 h of photolysis and continues up to 50 h of irradiation. No signs of decomposition of OOOT were observed after 100 h of photolysis in the presence of POM (see Figure 11). Further VOL. 35, NO. 11, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 10. Evolution and decay of intermediates upon photocatalytic degradation of atrazine as identified by their retention time. Conditions as in Figure 8.
FIGURE 11. Formation and decay of the intermediates CAAT, OAAT, and OOOT, the final organic product during photocatalytic degradation of atrazine in the presence of POM. Experimental conditions as reported in Figure 8. proof that the s-triazine ring remained intact in the photodegradation process was given by photolyzing OOOT in the presence of POM (SiW12O404-) for tens of hours. Contrary to what has been observed with all other pollutants, no blue color of the reduced POM was observed, implying no oxidation of OOOT in the absence of oxygen. OOOT presents strong resistance to further degradation by OH radicals. This, however, was expected, as kindly was pointed out by a referee, since the carbons in OOOT are fully oxidized (44). It is to be noted that OOOT also resists degradation upon photolysis with plain UV light (254 nm). Chloride and nitrate were identified as further final products of the photodegradation (Figure 12). Mechanistic Aspects: Comparison of US and Photolysis with POM Processes. As mentioned earlier, the high oxidizing ability, leading to the decomposition of various pollutants, is exclusively due to OH radicals formed during sonolysis. In addition, photodecomposition of pollutants in the presence of POM is mainly due to the formation of OH radicals. It is, therefore, not surprising that these two methods give similar overall results. However, it should be noted that Texier et al. (32, 33) ruled out the formation of OH radicals in photolysis with W10O324-. They draw this conclusion from the fact that no formation of H2O2 was detected in the absence of organic 2362
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FIGURE 12. Formation of chloride and nitrate ions depending on the time of irradiation of atrazine in the presence of SiW12O404-. Conditions as in Figure 8. substrate. In our opinion, this is not sufficient evidence. In the absence of organic species, the cage effect hinders OH radical escape to the bulk of the solution to encounter other OH radicals for the formation of H2O2. Instead, the reduced POM simply becomes reoxidized (i.e., an indirect electron hole recombination is to be considered). This should hold true for W10O324-, despite the long-lived intermediate detected (45, 46). According to Texier et al. (32, 33), three degradation intermediates [OIET and the amides 4-acetamido-2-chloro6-isopropylamino-s-triazine and 4-acetamido-2-chloro-6(ethylamino)-s-triazine], among the common ones, were not identified in the presence of W10O324- photocatalyst, in contrast with the TiO2 case. These results, according to the same authors, suggest hydrogen atom abstraction on the alkyl side chains of atrazine and, in a minor pathway, dehalogenation by electron transfer on the already dealkylated degradation products. It should be noted that detection of photogenerated OH radicals in the bulk of the solution is claimed in photocatalytic processes with TiO2 (47). These differences, observed in the photodecomposition of atrazine by TiO2 and W10O324-, suggest different reaction pathways of these two catalysts (32, 33). Looking at the appearance and decay of the first intermediates detected in the degradation of aqueous solutions of atrazine, namely, CAET, CIAT, and OIET, obtained by means of both sonolysis and photolysis with POM (see Figures 2 and 9), we draw the conclusion that the first sites of attack of OH radicals on atrazine units are the aminoalkyl groups of the side chains, as well as chlorine. Three other intermediates identified only by their retention time appear and decay in a similar time scale by both processes (Figures 3 and 10). The gradual replacement of the side chains by amino and finally by OH groups continues, as implied from the metabolites detected after several hours of treament by both methods as shown in Figures 4 and 11. The s-triazine ring remains intact, yielding OOOT as the final degradation product; i.e., all side groups of atrazine are replaced by OH groups. Nitrates and chloride ions together with carbon dioxide and water completed the final degradation products (Figures 4 and 11). Carbon dioxide could not be detected because of the small quantities produced from the alkyl carbons of the side chains. Its presence was inferred from the mineralization (formation of CO2, H2O, and inorganic anions) that all hydrocarbons, studied so far, undergo when subjected to photolysis with POM. Taking into consideration the extreme temperature and pressure conditions in the cavities, it seems to be rather
Scheme 1 shows the common pathway followed in sonolytic and photocatalytic (with POM) degradation of atrazine. Combined Effect of Sonochemical and Photocatalytic Decomposition of Atrazine with POM. Ultrasound and light powers were adjusted, to obtain comparable results as far as degradation of atrazine is concerned, by using these two methods separately. The combined effect of sonochemical and photocatalytic degradation of atrazine, in the presence of SiW12O404-, is shown in Figure 13. It can be seen that no synergistic effect was detected in the decomposition of aqueous solutions of atrazine. The result was cumulative; that is, it equaled the sum of the two individual processes.
Acknowledgments
FIGURE 13. Degradation of atrazine (7.0 × 10-5 M; pH 5.0 HClO4; 45 mL solution): (A) direct photolysis, λ > 320 nm; (B) photocatalytic degradation in the presence of SiW12O404-, 7.0 × 10-4 M, λ > 320 nm; (C) sonolysis using 850 kHz frequency; (D) combined photocatalytic and sonolytic decomposition of atrazine, as in (B) and (C).
SCHEME 1. Degradation Pathways for Photocatalytic Treatment in the Presence of SiW12O404- or for Sonochemical Treatment of Atrazine
surprising that the triazine ring does not break down during sonolysis. This then suggests that CA does not enter the cavities, which is in agreement with its high hydrophilicity, that keeps it outside the lipophilic cavitations. The final products and the intermediates involved show great similarities with the photodegradation of atrazine in the presence of TiO2 (15-19). This is to be expected since TiO2 acts, also, mainly, through OH radicals. Ozonation (14) and Fenton reagent (11) lead to the generation CAET, CIAT, CAAT, and several acetamide intermediates, whereas the metabolites involved upon treatment of atrazine with UVH2O2, to the best of our knowledge, have not been investigated thoroughly (10). Although no mineralization of atrazine could be obtained with either method, it is of interest to note that CA is reported to have essentially lower toxicity, when compared with atrazine and its degradation products (48). As described for TiO2 (19), dealkylation and deamination of the isopropyl amino group are favored relative to the ethyl amino group (see Figures 2 and 9).
We thank the Federal Ministry for Education, Research and Technology (Germany) and the Ministry for Development, General Secretariat for Research and Technology (Greece), for financial support framed by the Germany-Greece exchange program.
Literature Cited (1) The Agrochemical Handbook, 3rd ed.; Royal Society of Chemistry: Cambridge, England, 1994 (2) The pesticide manual, 7th ed.; Worthing, Ch., Ed., The British Crop Protection Council: Bracknell, U.K., 1983. (3) Commission of the European Communities: Pesticides in Ground and Drinking Water. In Water Pollut. Res. 1992, Report 27, 12. (4) Readman, J. W.; Albanis, T. A.; Barcelo, D.; Galassi, S.; Tronczynski, J.; Gabrielides, G. P. Mar. Pollut. Bull. 1993, 26, 613. (5) Tsipi, D.; Hiskia, A. Bull. Environ. Contam. Toxicol. 1996, 57, 250-257. (6) EC Council Directive relating to the quality of water intended for human consumption (1980/ 778/ EEC), Off. J. Eur. Commun. No L229/11-29. (7) Kontchou, C. Y.; Gschwind, N. J. Agric. Food Chem. 1995, 43, 2291. (8) Hapeman, C. J.; Karns, J. S.; Shelton, D. R. J. Agric. Food Chem. 1995, 43, 1383. (9) Behki, R. M.; Khan, S. U. J. Agric. Food Chem. 1994, 42, 1237. (10) Arantegui, J.; Prado, J.; Chamarro, E.; Esplugas, S. J. Photochem. Photobiol., A: Chem. 1995, 88, 65. (11) Arnold, S. M.; Hickey, W. J.; Harris, R. F. Environ. Sci. Technol. 1995, 29, 2083. (12) Huston, P. L.; Pignatello, J. J. Water Res. 1999, 33, 1238. (13) Balmer, M. E.; Sulzberger, B. Environ. Sci. Technol. 1999, 33, 2418. (14) Hapeman-Somich, C. J.; Gui-Ming, Z.; Lusby, W. R.; Muldoon, M. T.; Waters, R. J. Agric. Food Chem. 1992, 40, 2294-2298. (15) Minero, C.; Maurino, V.; Pelizzetti, E. Res. Chem. Intermed. 1997, 23, 291. (16) Pelizzetti, E.; Carlin, V.; Maurino, V.; Minero, C.; Dolci, M.; Marchesini, A. Soil Sci. 1990, 150, 523. (17) Pelizzetti, E.; Carlin, V.; Minero, C.; Pramauro, E.; Vincenti, M. Sci. Total Environ. 1992, 123/124, 161. (18) Pelizzetti, E.; Carlin, V.; Minero, C.; Gratzel, M. New J. Chem. 1991, 15, 351. (19) Pelizzetti, E.; Maurino, V.; Minero, C.; Carlin, V.; Pramauro, E.; Zerbinati, O.; Tosato, M. L. Environ. Sci. Technol. 1990, 24, 1559. (20) Petrier, C.; David, B.; Laguian, S. Chemosphere 1996, 32, 1709. (21) Torrents, A.; Anderson, B. G.; Bilboulian, S.; Johnson, W. E.; Hapeman, C. J. Environ. Sci. Technol. 1997, 31, 1476. (22) Pope, M. T. Heteropoly and Isopoly Oxometalates in Inorganic Chemistry Concepts 8; Jorgensen, C. K., et al., Eds.; SpringerVerlag: West Berlin, 1983. (23) Mylonas, A.; Roussis, V.; Papaconstantinou, E. Polyhedron 1996, 15, 3201. (24) Mylonas, A.; Papaconstantinou, E. J. Mol. Catal. 1994, 92, 261. (25) Mylonas, A.; Papaconstantinou, E. J. Photochem. Photobiol., A: Chem. 1996, 94, 77. (26) Einaga, H.; Misono, M. Bull. Chem. Soc. Jpn. 1997, 70, 1551. (27) Einaga, H.; Misono, M. Bull. Chem. Soc. Jpn. 1996, 69, 3435. (28) Mylonas, A.; Hiskia, A.; Papaconstantinou, E. J. Mol. Catal. 1996, 114, 191. VOL. 35, NO. 11, 2001 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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(29) Hiskia, A.; Mylonas, A.; Tsipi, D.; Papaconstantinou, E. Pestic. Sci. 1997, 50, 171. (30) Hoffmann, M. R.; Hua, I.; Ho¨chemer, R. Ultrason. Sonochem. 1996, 3, 163. (31) Suslick, K. S. Sci. Am. 1989, 260 (2), 80. (32) Texier, I.; Ouazzani, J.; Delaire, J.; Giannotti, C. Tetrahedron 1999, 55, 3401. (33) Texier, I.; Giannotti, C.; Malato, S.; Richter, C.; Delaire, J. Catal. Today 1999, 54, 297. (34) Pope, M. T.; Varga, G. M. Inorg. Chem. 1966, 5, 1249. (35) Cook, A. M.; Hutter, R. J. Agric. Food Chem. 1981, 29, 1133. (36) Henglein, A. In Advances in Sonochemistry; Mason, J. J., Ed.; JAI Press, Ltd.: London, 1993; Vol. 3, p 17. (37) Lorimer, J. P.; Mason, T. J. Chem. Soc. Rev. 1987, 16, 239. (38) Petrier, C.; Micolle, M.; Merlin, G.; Luche, J.-L.; Reverdy, G. Environ. Sci. Technol. 1992, 26, 1639. (39) Makino, K.; Mossoba, M.; Riesz, P. J. Phys. Chem. 1983, 87, 1369. (40) Wakeford, C. A.; Blacuburn, R.; Lieniss, P. D. Ultrason. Sonochem. 1999, 6, 141 and references therein.
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(41) Mylonas, A.; Hiskia, A.; Androulaki, E.; Dimotikali, D.; Papaconstantinou, E. Phys. Chem. Chem. Phys. 1999, 1, 437. (42) Hiskia, A.; Papaconstantinou, E. Inorg. Chem. 1992, 31, 163. (43) Yamase, T.; Kurozumi, T. J. Chem. Soc., Dalton Trans. 1983, 2205. (44) Erickson, R. L.; Lee, K. S. Crit. Rev. Environ. Control 1989, 19, 1. (45) Duncan, D. C.; Fox, M. A. J. Phys. Chem. A 1998, 102, 4559. (46) Tanielian, C.; Duffy, K.; Jones, A. J. Phys. Chem. B 1997, 101, 4276. (47) Peterson, M. W.; Turner, J. A.; Nozik, A. J. J. Phys. Chem. 1991, 95, 221. (48) Canelli, E. Am. J. Public Health 1974, 64, 155.
Received for review September 11, 2000. Revised manuscript received February 5, 2001. Accepted February 23, 2001. ES000212W
