Photocatalytic wastewater treatment combined with ozone


Photocatalytic wastewater treatment combined with ozone pretreatment. Keiichi Tanaka, Keiji Abe, Chen Yin Sheng, and Teruaki Hisanaga. Environ. Sci...
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Environ. Sci. Techno/. 1992, 26, 2534-2536

(3) Mueller, J. G.; Chapman, P. J.; Pritchard, P. H. Environ. Sci. Technol. 1989,23, 1197-1201. (4) Martin, J. H., Jr.; Siebert, A. J.; Loehr, R. C. J. Environ. Eng. 1991,117,291-299. (5) Baugh, A. L.; Lovegreen, J. R. In Petroleum Contaminated Soils; Kostecki, P. T., Calabrese, E. J., Ede.; Lewis: Chelsea, MI, 1990; Vol. 3, Chapter 12. (6) Song,H.-G.; Wang, X.; Bartha, R. Appl. Environ. Microbiol. 1990,56,652-656. (7) Wang, X.; Bartha, R. Soil Biol. Biochem. 1990,22,501-505. ( 8 ) Mahaffey, W. R.; Compeau, G.; Nelson, M.; Kinsella, J. Water Sci. Technol. 1991,3, 83-88. (9) Fuhr, B. J.; Holloway, L. R.; Reichert, C. AOSTRA J. Res. 1986, I, 281-288. (10) Selucky, M. Anal. Chem. 1983,55, 141-143. (11) Behar, F.; Pelet, R. J. Anal. Appl. Phys. 1984, 7,121-135. (12) Fuhr, B. J.; Holloway, L. R.; Reichert, C. J. Can. Petrol. Technol. 1986,25 (51, 28-32. (13) Fuhr, B. J.; Holloway, L. R.; Reichert, C.; Barua, S. K. J. Chromatogr. Sci. 1988,26, 55-59. (14) Poirier, M.-A,; George, A. E. J . Chromatogr. Sci. 1983,21, 331-333. (15) Poirier, M.-A.; Rahimi, P.; Ahmed, S. M. J. Chromatogr. Sci. 1984, 22, 116-119. (16) Speight, J. Proceedings: International Symposium on

Characterization of Heavy Crude Oils-and Petroleum Residues; June 25-27,1984, Lyon, France, Editions Technip:

Paris, France, 1984; pp 32-41. (17) Enminger, J. D.; Ahlert, R. C. Environ. Technol. Lett. 1987, 8, 269-278. (18) Clement International Corp. Toxicological Profile for Creosote. TP-90-09; Agency for Toxic Substance and

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University of Denmark, Lyngby, Technomic: Lancaster, PA, 1988; pp 828-847. (24) Fedorak, P. M.; Grbic-Galic, D. Appl. Environ. Microbiol. 1991,57,932-940. (25) Semple, K. M.; Cyr, N.; Fedorak, P. M.; Westlake, D. W. S. Can. J. Chem. 1990,68, 1092-1099. (26) Westlake, D. W. S.; Jobson, A.; Phillippe, R.; Cook, F. D. Can. J . Microbiol. 1974, 20, 915-928. (27) Bossert, I.; Bartha, R. In Petroleum Microbiology; Atlas, R. M., Ed.; Macmillan: New York, 1984; pp 435-473. (28) Huddleston, R. L.; Cresswell, L. W. Proceedings: Man-

agement of Petroleum Refinery Wastewaters Forum; EPA/API, WPRA & UT, Tulsa, OK, 1976. (29) Bulman, T. L.; Jank, B. E.; Scrooggins, R. P. In Petroleum Contaminated Soils; Kostecki, P. T.; Calabrese, E. J., Eds.; Lewis: Chelsea, MI, 1990; Vol. 3, Chapter 5. (30) Hosler, K. R.; Bulman, T. L.; Booth, R. M. Presented at Sixth Annual Conference on Hydrocarbon Contaminated Soils: Analysis, Fate, Environmental & Public Health Effects, University of Massachusetts, Amherst, MA, Sept 23-26, 1991. (31) Atlas, R. M. Microbiol. Rev. 1981, 45, 180-209. (32) Volkman, J. K.; Holdsworth, D. G.; Neill, G. P.; Bavor, H. J., Jr. Sci. Total Environ. 1992, 112, 203-219. (33) Mueller, J. G.; Lantz, S. E.; Blattmann, B. 0.;Chapman, P. J. Environ. Sci. Technol. 1991, 25, 1045-1055. (34) Ellis, B.; Harold, P.; Kronberg, H. Environ; Technol. 1991, 12,447-459.

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Received for review April 29,1992. Revised manuscript received August 17, 1992. Accepted August 28, 1992. This work was primarily funded by Alberta Environment, through the Alberta Help End Landfill Pollution Project, by an Imperial Oil Ltd. University Research Grant, by grant support from the Natural Sciences and Engineering Research Council, and infrastructure funding of the Environmental Health Program provided by CN Rail Ltd., Shell Canada Ltd., and Weldwood of Canada Ltd. The Alberta Research Council provided initial financial support for S.J.P.

COMMUNICATIONS Photocatalytic Wastewater Treatment Combined with Ozone Pretreatment Kellchl Tanaka," KelJIAbe, Chen Yln Sheng,?and Teruakl Hlsanaga National Chemical Laboratory for Industry, Higashi 1-1, Tsukuba, Japan Introduction The photocatalytic process provides a new method for wastewater treatment (1). In this process, pollutants are degraded by strong oxidizing power generated on an illuminated surface of a catalyst. The advantage of this method is that many pollutants degrade fairly rapidly and only a small amount of intermediate products are formed (2, 3). However, some stable compounds, such as agricultural chemicals, take a long time to be completely +Permanentaddress: Chemical Engineering Design & Research Institute, Wulmiqi, Xinjiang, China. 2534

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mineralized (4). This is one of the great obstacles to the practical application of this method. We found that pretreatment by ozonation prior to photocatalytic treatment facilitates the degradation of pollutants greatly. Experimental Section The TiOz used throughout the experiment was a Katayama product (rutile). Ita specific surface area is 2.7 m2/g. DEP (dimethyl 2,2,2-trichloro-l-hydroxyethylphosphonate) and asulam (sodium N-methoxycarbonylsulfanilamide) were reagent grade. Fenitrothion (0,O-dimethyl 0-4-nitro-m-tolyl phosphorothioate) in emulsified solution

0013-936X/92/0926-2534$03.00/0

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Flgure 1. Degradation of fenltrothion by ozonatlon and photocatalytic treatment: 0,ozonatlon; A, photocatalytic treatment.

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Flgure 3. TOC reductlon of asulam solutlon by ozonation and photocatalytic treatment: 0, ozonation; A,photocatalyt\ctreatment: X , A, photocatalytic treatment after ozonatlon.

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Figure 2. TOC reduction of a fenitrothion solution by ozonatlon and photocatalytic treatment: 0,ozonation; A, photocatalytictreatment; 0, photocatalytlc treatment after ozonation.

is a commercial product available for practical use and contains about 50% xylene and emulsifier. This grade was employed purposely to test the practicability of the present process. The photocatalytic degradation experiments were carried out as follows. A 75-mg sample of Ti02was suspended in 25 mL of solution in a Pyrex glass bottle. The bottle was illuminated through a water filter by a 500-W super-high-pressure mercury lamp a t a distance of 40 cm from a focusing lens. The intensity of the light after passing through the water filter was 18 mW/cm2 in the 330-390-nm region. After illumination, Ti02was filtered off and the filtrate was subjected to analysis. Total organic carbon (TOC) was measured by a Shimadzu TOC analyzer 500. For ozonation, an initial volume of 250 mL of the solution was bubbled in a glass cylinder a t a flow rate of 2.0 g/h at room temperature. About 13 w t % ozone is contained in the applied gas. The pH of the solution was not adjusted and was 8.4 and 4.0 for 3.3 X M fenitrothion and 2.5 X M asulam (240ppm TOC), respectively, before illumination.

Results and Discussion The degradation of fenitrothion by ozonation and photocatalytic treatment was followed by measuring the disappearance of ita peak in HPLC (Figure l). It degraded fairly rapidly. However, its complete degradation to C02 was very slow. Figure 2 shows the variation in TOC of the solution with ozonation and photocatalytic treatment individually. TOC decreased only slightly with either method. Similarly, 600 ppm asulam was degraded rapidly by ozonation. But the TOC concentration was decreased only

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Figure 4. TOC reduction of DEP solution by ozonatlon and photoozonation; A, photocatalytic treatment; x , . , catalytic treatment: 0, photocatalytic treatment after ozonatlon.

slightly by either ozonation or photocatalytic treatment (Figure 3). However, ozonation prior to photocatalytic treatment reduced the TOC of the solutions of both fenitrothion and asulam (Figures 2 and 3): The longer the ozone pretreatment time, the faster the TOC reduction by photocatalytic treatment. Spectroscopic study of the solutions of fenitrothion and asulam showed the rapid disappearance of aromatic ring absorption a t 270 nm with ozonation. The formation of several organic acids was confirmed by ion chromatography. It was thus suggested that ozone pretreatment degrades fenitrothion and asulam into hydrophilic compounds. On the other hand, in the direct photocatalytic degradation, the disappearance rate of 270-nmabsorption was slow and fairly close to the TOC elimination rate. This indicates that the degradation of the aromatic nucleus leads immediately to the formation of C02 and therefore relatively small amounts of intermediate products are produced in the photocatalytic method. The effect of ozone pretreatment is not confined to aromatic compounds. The photocatalytic degradation of DEP was also enhanced by ozone pretreatment (Figure 4). Upon degradation of DEP, Pod3and C1- are formed as final products (5). The formation of both ions during a 6-h ozonation was only about 15 and 30% of calculated and C1-, respectively. I t was thus sugvalues for Po43gested that ozonation formed oxidized compounds which still retained P and C1. Photocatalytic treatment after ozonation increased the release of P and C1 and resulted in the formation of the calculated amounts of PO4$ and C1- after 5 h (Figure 5). Even photocatalytic degradation Environ. Sci. Technol., Vol. 28, No. 12, 1992 2535

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biodegradable ones. A similar mechanism holds for the present process. Ozonation produces more photocatalytically degradable substances. Neither the photocatalytic method nor ozonation alone eliminates TOC from a solution of chemically stable compounds. However, photocatalytic treatment following ozonation can mineralize these compounds completely.

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Literature Cited O b ,D. F.; Pelhetti, E.; Serpone, N. Enuiron. Sei. Technol. 1991,25,1522-1529.

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Flguro 5. Formation of Ci- and PO,” by ozonatlon and photocatalytic treatment of DEP solution. InRiai concentration of DEP is 0.6 X lo9 moi/L. Ozonation: 0 , Ci-; A,PO:-. Photocatalytic treatment after 4-h ozonatlon: 0, CI-, A, PO,3-.

alone produced these ions faster than ozonation, but the formation rate was slower than after ozone pretreatment. It has been known that biological treatment of wastewater is facilitated by ozone pretreatment (6, 7). The mechanism has been considered to be that ozonation transforms hardly biodegradable compounds into more

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D’Oliveira, J.-C.; Al-Sayyed, G.; Pichat, P. Environ. Sei. Technol. 1990,24,990-996.

Al-Sayyed, G.; D’Oliveira, J.-C.; Pichat, P. J.Photochem. Photobiol. A 1991, 58, 99-114.

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Gilbert, E. Water Res. 1980, 14, 1637-1643. Gilbert, E. Water Res. 1988, 22, 123-126. Received for review May 21,1992. Revised manuscript received September 1, 1992. Accepted September 9, 1992.