Photocatalytic Degradation of Acid Chrome Blue K with Porphyrin

Aug 28, 2008 - State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People...
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14878

J. Phys. Chem. C 2008, 112, 14878–14882

Photocatalytic Degradation of Acid Chrome Blue K with Porphyrin-Sensitized TiO2 under Visible Light Di Li,† Wenjun Dong,‡ Shangmei Sun,§ Zhan Shi,*,† and Shouhua Feng† State Key Laboratory of Inorganic Synthesis and PreparatiVe Chemistry, College of Chemistry, Jilin UniVersity, Changchun 130012, People’s Republic of China, Center for Optoelectronics Materials and DeVices, Department of Physics, Zhejiang Sci-Tech UniVersity, Hangzhou 310018, People’s Republic of China, and Department of Chemistry, College of Science, Yanbian UniVersity, Yanji 133002, People’s Republic of China ReceiVed: January 13, 2008; ReVised Manuscript ReceiVed: July 18, 2008

We have investigated an application of TiO2 photocatalyst sensitized with meso-tetra (4-carboxyphenyl) porphyrin (H2TPPC) or meso-tetra (4-nitrophenyl) porphyrin (TNO2PP) to degrade acid chrome blue K (ACBK) under visible light irradiation. By injecting electrons from the photoexcited sensitizer to the conduction band, the sensitized TiO2 degraded acid chrome blue K under incandescent lamp irradiation. The results indicated that H2TPPC-TiO2 had remarkable effects on the photodegradation of ACBK under natural sunlight (NSL) irradiation. The initial concentration of ACBK of 10 mg/L gave the decolorization rate of ACBK under incandescent lamp irradiation up to 94% in 15 min. This confirms that the H2TPPC-TiO2 composite could fully decompose ACBK under artificial light and that this process was accelerated under NSL. All facts suggest that H2TPPC-TiO2 in the heterogeneous photocatalysis phase has a potential application in wastewater treatment by using NSL. 1. Introduction Conventional techniques of removing organic pollutants from water resources and the water supply system are usually focused on sedimentation, flocculation, steam stripping, adsorption with activated carbon, filtration, etc. Although adsorption may transfer some pollutants from an aqueous solution to solid phase,1 the total quantity or hazardous potential of the pollutants may not be discernibly reduced, not to mention that some pollutants are poorly or not even absorbed by activated carbon. Photocatalytic reaction has been studied since 1972 when the photolysis of water was discovered using TiO2 as a photocatalyst.2 Recently, much work has been undertaken on the detoxification of pollutants in both air and water, while the main focus has been on the study of the surface-modified semiconductors for photocatalysis.3 TiO2 is the most commonly utilized photocatalyst because some of its forms have reasonable photoactivity.4 Besides, it has many advantages such as being nontoxic, insoluble and comparatively inexpensive. However, the light absorption region of anatase-typed TiO2 particles (λ e 385 nm) does not fit with the solar spectrum because the solar energy above 3.0 eV (λ e 410 nm) only makes up less than 5% of whole sunlight.5 Therefore, the development of low-band gap photoactive material, that is, the so-called visible light photocatalysts, is strongly urged for solving environmental and energy problems. Alternatively, in view of low cost and feasibility, it is desirable to incorporate the TiO2 catalyst with visible light response via composition.6,7 Dye sensitization is considered to be an efficient method to modify the photoresponse properties of TiO2 particles. The dyes used are erythrosine B,8 rose bengal,9 metal porphyrin,10-12 etc., among which metal porphyrin may be an appropriate candidate because of its high absorption * To whom correspondence should be addressed. E-mail: zshi@ mail.jlu.edu.cn. † Jilin University. ‡ Zhejiang Sci-Tech University. § Yanbian University.

coefficient within the solar spectrum and its good chemical stability in comparison to that of other dyes. The chemistry of porphyrin derivatives has played an important role especially during the past decade in particular branches of new materials science, and many researchers have undertaken projects on the synthesis of variously substituted compounds to obtain new functional materials.13-15 Porphyrin derivatives have been found to possess application for the construction of solar cells as light absorbents in organic dyes displaying notable stability and unique chemical, physical, and spectroscopic properties.16-18 Recently, the photocatalytic activity of TiO2 powders impregnated with lipophilic Cu porphyrins used as sensitizers for the decomposition of 4-nitrophenol has been investigated.19,20 TiO2 samples impregnated with functionalized Cu porphyrins are more efficient catalysts compared to bare TiO2 for the photodegradation of 4-nitrophenol. In this article, the photocatalytic oxidation of H2TPPC-TiO2 or TNO2PP-TiO2 under incandescent lamp irradiation is investigated for the first time. Considerable degradation of ACBK over H2TPPC-TiO2 and TNO2PP-TiO2 is revealed, and the charge-transfer mechanism in H2TPPC-TiO2 and TNO2PP-TiO2 samples is discussed. 2. Experimental Section 2.1. Materials. H2TPPC and TNO2PP were prepared, purified and characterized according to the previous report.21,22 TiO2 nanoparticles (P25, d ) 21 nm) were purchased from Beijing Entrepreneur Science & Trading Co. ACBK was of analytical reagent grade quality and was used without further purification. Other chemicals were commercial products of analytical grade or reagent-grade. All the solutions were prepared with distilled water. 2.2. Preparation of TiO2 Nanoparticles Modified with H2TPPC and TNO2PP. TiO2 nanoparticles modified with H2TPPC and TNO2PP were prepared by mixing 1 g of TiO2 nanoparticles and 50 mg of H2TPPC or TNO2PP in DMF, and

10.1021/jp800318k CCC: $40.75  2008 American Chemical Society Published on Web 08/28/2008

Photocatalytic Degradation of Acid Chrome Blue K

Figure 1. High resolution XPS of the Ti (2p) regions.

J. Phys. Chem. C, Vol. 112, No. 38, 2008 14879 2.4. Photocatalytic Oxidative Degradation. The photocatalytic oxidative degradation of ACBK in the aqueous solutions was studied by using H2TPPC-TiO2 and TNO2PP-TiO2 as the photocatalyst under room temperature and normal atmosphere pressure. H2TPPC-TiO2 (50 mg) (TNO2PP-TiO2 70 mg) and 50 mL of 10 mg/L of ACBK aqueous solution were added into the reactor then stirred with a magnetic stirrer prior to irradiation with incandescent lamp or FHPML at room temperature. After the reaction, the sample solution was centrifuged to remove H2TPPC-TiO2 or TNO2PP-TiO2 particles from solution. The solution obtained this way was extracted into a quartz cell. The absorbance of the samples was measured with quartz cells every 5 min. 2.5. Approach of Calculation. The degradation rate of ACBK in the reaction process could be calculated by the following formula:

Decolorization rate ) (A0 - At)/A0 × 100 % where At is the absorbance of ACBK measured at 492 nm at time t, and A0 is the initial absorbance prior to reaction. The residual concentrations of ACBK could be calculated by the following formula:

Ct)At /A0×C0 where Ct is residual concentration of ACBK at time t (mg/L), and C0 is the initial concentration of ACBK (10 mg/L). Figure 2. The UV-vis absorption spectra of TiO2, H2TPPC-TiO2, and TNO2PP-TiO2.

DMF was heated to reflux for five hours. After adsorbing H2TPPC or TNO2PP, TiO2 nanoparticles were filtered, washed with DMF until the filtrate was colorless, then washed five times with distilled water, and dried to obtain samples of H2TPPC-TiO2 and TNO2PP-TiO2. TGA signals associated with the analysis of H2TPPC-TiO2 and TNO2PP-TiO2 are shown in Supporting Information (Figures 1 and 2). The signals provide supportive evidence for the amount of porphyrin adsorbed on TiO2 nanoparticles and the amount of porphyrin lost during the above process. About 21 mg of H2TPPC was absorbed by 1 g of TiO2 nanoparticles, and 29 mg of H2TPPC was removed by washing with DMF. Similarly, about 9 mg of TNO2PP was absorbed by 1 g of TiO2 nanoparticles, and 41 mg of TNO2PP was removed by washing with DMF. 2.3. Characterizations. The degradation rates of ACBK solutions were periodically scanned by a UV-2450 spectrophotometer (Shimadzu, Japan), and the maximum absorption wavelength of ACBK solution was identified at 526 nm. UV-vis spectra data were recorded in the range from 200 to 800 nm. UV-vis absorption spectra of TiO2, H2TPPC-TiO2 and TNO2PP-TiO2 were scanned by Lambda 20 (Picker, USA). Irradiation was carried out with 200W incandescent lamp and 450W fluorescent high-pressure mercury lamp (FHPML). A distance of about 12 cm between the lamp and reactor was maintained. XPS measurements were performed with Thermo ESCALAB 250 and equipped with nonmonochromatizedsource (operating at 150 W). EPR measurements were carried out at room temperature with a JEOL JES-FA200 spectrometer. Computer simulations were used when necessary to check spectral parameters. Aliquots of the catalyst (100 mg) were placed into a quartz cell with greaseless stopcocks. Irradiation treatments at room temperature were carried out by placing the cell in a quartz Dewar flask employing high-pressure mercury lamp (500 W, maximum at 365 nm).

3. Results and discussion 3.1. XPS Studies. XPS, a highly surface-selective technique, can distinguish different forms of surface or bulk material. The spectra of the Ti (2p) regions are shown in Figure 1. The Ti (2p3/2) binding energy values of TiO2, H2TPPC-TiO2 and TNO2PP-TiO2 are 458.47, 458.14 and 458.25, respectively. The peaks that are attributable to H2TPPC-TiO2 and TNO2PP are shifted to lower binding energies, i.e., the Ti (2p3/2) peaks. These data suggest that Ti atom as the acceptor coordinates with oxygen atom in H2TPPC-TiO2 and that the oxygen atom provides electrons. When the density value of the layer electron cloud increases, the internal lay electrons shielded by Ti atom also increases, leading to the decrease in the binding energies of the internal layer. This suggests that H2TPPC adsorbs on the surface of TiO2 with carboxyl as the coordinating group better than TNO2PP.23,24 The adsorption mechanism of TNO2PP on the TiO2 surface can be attributed to the weak chemisorption.24 3.2. UV-Vis Properties of TiO2, H2TPPC-TiO2 and TNO2PP-TiO2 Photocatalysts. Figure 2 shows the UV-vis absorption spectra of TiO2, TNO2PP-TiO2 and H2TPPC-TiO2 samples. Obviously, there is no absorption above 400 nm for TiO2, while H2TPPC and TNO2PP show visible light absorption from 400 to 700 nm. Consequently, H2TPPC-TiO2 and TNO2PP-TiO2 composites exhibit a broader absorption range for the solar spectrum than pure TiO2. 3.3. Optimal Adding Amount of Photocatalyst. When the initial concentration 10 mg/L of ACBK was used, adding different amounts of H2TPPC-TiO2 (30, 50, 70 and 100 mg) showed 55.57%, 92.42%, 99.01% and 99.32% decolorization rates, respectively, under fluorescent high-pressure mercury lamp after 10 min. The decolorization rates were 53.10%, 83.70%, 96.14% and 97.98% under fluorescent high-pressure mercury lamp after 30 min by adding different amounts of TNO2PP-TiO2 with 30, 50, 70 and 100 mg, respectively. But the fastest is not the best. ACBK could be adsorbed by H2TPPC-TiO2 or TNO2PP-TiO2 so firmly that the photocatalysis efficiency of H2TPPC-TiO2 or TNO2PP-TiO2 was

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Figure 3. Decrease of ACBK under various photocatalytic conditions (the temperature ) 298 K; ACBK concentration ) 10 mg/L): (a) 50 mg of H2TPPC-TiO2 in the dark; (b) 50 mg of H2TPPC-TiO2 under FHPML; (c) 70 mg of TNO2PP-TiO2 in the dark; (d) 70 mg of TNO2PP -TiO2 under FHPML.

reduced. The nanoparticles needed much more time to degrade ACBK, which was absorbed by H2TPPC-TiO2 or TNO2PP-TiO2. After adding different amounts of H2TPPC-TiO2 (30, 50, 70 and 100 mg) and stirring in the dark, the absorbance of ACBK solutions declined with stirring time, but the loss of ACBK was 16.67%, 48.18%, 75.99% and 96.39%, respectively, in 10 min. On the basis of the experimental results, the optimal adding amount of H2TPPC-TiO2 was 50 mg. Similar to H2TPPC-TiO2, the absorbance of ACBK solutions declined with stirring time after adding different amounts of TNO2PP-TiO2 (30, 50, 70 and 100 mg) and stirring in the dark, but the loss of ACBK was 15.95%, 30.38%, 52.74% and 84.50%, respectively, in 30 min. On the basis of the experimental results, the optimal adding amount of TNO2PP-TiO2 was consequently determined as 70 mg. Therefore, the photocatalysis efficiency of H2TPPC-TiO2 is better than that of TNO2PP-TiO2. 3.4. Influence of the Amount of Porphyrin Absorbed on TiO2 to the Photocatalyst. We added different amounts of H2TPPC (15 mg and 10 mg) with 1 g TiO2 to DMF, which was then heated to reflux for five hours. After adsorbing H2TPPC, the TiO2 nanoparticles were filtered, and the filerate was colorless with no UV-vis absorption, indicating that all the porphyrins had been absorbed on TiO2. In comparison with the experiment described previously, when 50 mg of H2TPPC reacted with 1 g of TiO2, only 21 mg of H2TPPC was absorbed on TiO2; therefore, 21 mg of H2TPPC might be the maximum amount of absorption of 1 g of TiO2. H2TPPC-TiO2 (50 mg) of the above three different absorption amounts was added into 50 mL of ACBK solution. Under the irradiation of fluorescent high-pressure mercury lamp for 15 min, the decolorization rates were 92.42% (21 mg of H2TPPC/1 g TiO2), 85.16% (15 mg of H2TPPC/1 g TiO2) and 79.11% (10 mg of H2TPPC/1 g TiO2). Therefore, the optimum amount of porphyrin absorbed on TiO2 was 21 mg. 3.5. Kinetics of ACBK Photocatalytic Degradation. On the basis of the experimental procedures described above, the photocatalytic degradation of ACBK in aqueous solutions was investigated at various conditions (see Figure 3), and it was found that ACBK solutions could be well adsorbed by H2TPPC-TiO2 and TNO2PP-TiO2. After stirring in the dark, the absorbance of ACBK solutions declined with stirring time, but the loss of ACBK was limited within 55% (Figure 3, curves a and c). Under the irradiation of fluorescent high-pressure mercury lamp, the reducing quantity reached above 90% in 30 min reaction, which confirmed that H2TPPC-TiO2 and

Li et al. TNO2PP-TiO2 had a better photocatalytic activity (Figure 3, curves b and d). The rapid decomposition that occurred is consistent with the notion that relatively strong adsorption enhances photooxidation on the H2TPPC-TiO2 surface.25-27 If the primary degradation of curves b and d in Figure 3 theoretically obeys the first-order kinetic law, they must follow the equation as -dCt/dt ) k1Ct, where Ct is the residual concentration of ACBK solution at time t based on Ct ) (At/ A0) × C0 calculation, and ka is the first order decay constant. To confirm the characteristics of the above three curves, the slopes of lines plotted with ln Ct versus irradiation time were determined by regression analysis, as listed in Table 1. It was found that the deduced model was well matched with -dCt/dt ) k1Ct. The fact that the plot of ln Ct versus t appeared as a linear lines suggests that the reaction exactly followed the firstorder kinetic law. 3.6. Potential Applicability of H2TPPC-TiO2. According to the above studies, we find that the photocatalysis efficiency of H2TPPC-TiO2 to degrade ACBK is better than that of TNO2PP-TiO2. To demonstrate the potential applicability of H2TPPC-TiO2, we investigated its photocatalytic activity relative to a commercial photocatalyst (P25 titania), with the photocatalytic degradation of ACBK as a test reaction. The characteristic absorption of ACBK at 526 nm was chosen as the monitored parameter for the photocatalytic degradation process. A further comparative experiment was carried out to investigate the catalytic activity. The solution of ACBK was subjected to a series of experimental conditions: (a) no catalyst under FHPML; (b) no catalyst under incandescent lamp; (c) with P25 titania (50 mg), in the dark; (d) with H2TPPC-TiO2 (50 mg), in the dark; (e) with P25 titania (50 mg) and FHPML; (f) with H2TPPC-TiO2 (50 mg) and FHPML; (g) with P25 titania (50 mg) and incandescent lamp; (h) with H2TPPC-TiO2 (50 mg) and incandescent lamp; and (i) with H2TPPC-TiO2 (50 mg) and FHPML while air was blown by a small air pump. The results are illustrated in Figure 4. As can be seen from the spectra, ACBK solution could be stably reserved under the irradiation of fluorescent high-pressure mercury lamp (curve a) or incandescent lamp (Curve b) in fifteen minutes. An obvious decrease in the concentration of ACBK took place in the presence of H2TPPC-TiO2 (curve d) in the dark, compared to that in the presence of P25 (curve c) in the dark. This decrease may be mainly ascribed to the adsorption of ACBK on the surface, although without exposure to FHPML or an incandescent lamp. The concentration of the ACBK solution hardly changed after mixing the solution with the catalysts for 5 min, indicating that the adsorption of ACBK on nanostructured catalysts reached an equilibrium state. However, curves e (P25), f (H2TPPC-TiO2), g (P25) and h (H2TPPC-TiO2) clearly show that the H2TPPC-TiO2 photocatalyst has much greater activity than that of P25 under identical conditions with exposure to FHPML or an incandescent lamp. When air was blown by a small air pump, more oxygen joined in the photocatalytic activity, and more hydroxyl radicals were produced by H2TPPC-TiO2; therefore, the degradation rate was accelerated (curve i). The degradation of ACBK in H2TPPC-TiO2 follows first-order kinetics. Exposure of the solution of ACBK to incandescent lamp whose luminous efficiency is lowest for 15 min also resulted in complete decolorization. This difference in the photocatalytic activity between H2TPPC-TiO2 and P25 can be explained by the stronger adsorption of H2TPPC-TiO2 to the molecules of ACBK and more hydroxyl radicals produced

Photocatalytic Degradation of Acid Chrome Blue K

J. Phys. Chem. C, Vol. 112, No. 38, 2008 14881

TABLE 1: Kinetic Parameters under the Effects of a Fluorescent High-Pressure Mercury Lamp catalyst

kinetic equation

k1 (min-1)

half-life (min)

decolorization rate (%)

H2TPPC-TiO2 TNO2PP-TiO2

ln Ct ) 2.3026 - 0.1880t ln Ct ) 2.3026 - 0.1085t

0.1880 0.1085

3.6872 6.3889

94.04 96.14

by H2TPPC-TiO2, which leads to a rapid degradation on the active surface area. ACBK solutions irradiated with different light sources had a manifest variety of degradation rates as shown in Figure 4. In the photocatalytic degradation of ACBK by H2TPPC-TiO2, the reaction rate was related to the wavelength of light source in addition to lamp power. The degradation rate was increased with power-strengthening. The emission spectra of incandescent lamp and FHPML are shown in the Supporting Information. It was observable that the emission spectra of FHPML mainly focused on visible light, and the emission spectra of incandescent lamp mostly focused on visible light and near-infrared. Nevertheless, the spectrum of NSL was continuously alternated from ultraviolet to infrared. NSL with the continuous spectrum could not only promote the production of •OH, but could also induce further photocatalytic degradation of ACBK by using H2TPPC-TiO2. For practical application in the water-treatment procedure, NSL should be chosen as an ideal source for irradiation. 3.7. EPR Studies. EPR spectroscopy is an especially suitable technique for the detection of photogenerated radicals, which act as intermediates in the photocatalytic processes. Here we used porphyrin-sensitized TiO2 to investigate the interfacial electron process and directly observed the EPR signal of O3at room temperature under the irradiation of high-pressure mercury lamp. Results of the EPR signals from H2TPPC-TiO2 and TNO2PP-TiO2 irradiated by high-pressure mercury lamp are shown in Figure 5. The spectrum obtained this way for H2TPPC-TiO2 and TNO2PP-TiO2 exhibits two features: g(H2TPPC-TiO2) ) 2.00218 and g(TNO2PP-TiO2) ) 2.00188. The intensity of the EPR signal of H2TPPC-TiO2 increased considerably compared with TNO2PP-TiO2. Because the EPR signal can be ascribed to O3-,28 this means that there are more photogenerated O3- species in H2TPPC-TiO2 than in TNO2PP-TiO2. The interpretation of the EPR data observed in this study can be achieved using the well-established reaction scheme known to occur during the UV irradiation of H2TPPC-TiO2 and

Figure 4. Photodegradation of ACBK (10 mg/L, 50 mL) under different conditions: (a) no catalyst under FHPML; (b) no catalyst under incandescent lamp; (c) with P25 titania (50 mg), in the dark; (d) with H2TPPC-TiO2 (50 mg), in the dark; (e) with P25 titania (50 mg) under FHPML; (f) with H2TPPC-TiO2 (50 mg) under FHPML; (g) with P25 titania (50 mg) under incandescent lamp; (h) with H2TPPC-TiO2 (50 mg) under incandescent lamp; and (i) with H2TPPC-TiO2 (50 mg) under FHPML (air was blown).

TNO2PP-TiO2. The absorption of photons leads to the generation of electron-hole pairs (either associated in excitons or as free carriers) in H2TPPC-TiO2 and TNO2PP-TiO2.

Porphyrin(S0) + hV f Porphyrin *(S1)

(1)

+

Porphyrin *(S1) + TiO2 f Porphyrin + TiO2(e¯ ) (2) These charge carriers can be trapped at several centers. Porphyrin cation:

Ti4+ - O2j + Porphyrin+ f Porphyrin(S0) + Ti4+ - O¯ (3) When O2 molecules are present, as is the case of part of the experiments presented here, they also participate in the charge carrier trapping processes, generating surface ozonide ions.29,30

Ti4+ - O¯ + O2 f Ti4+ - O3j

(4)

e¯ + O2 f O2j

(5)

However, continued capture of photogenerated electrons can also originate diamagnetic species.28 2O2 + e f O2

(6)

If adsorbed oxygen is present, it can further react with the adsorbed peroxide according to the following equations.

O22- + O2 f 2O- + 2O2-

(7)

O¯ + O2 f O3j

(8)

It is worth noting that O22- can be also formed from the capture of electrons (i.e., reaction 6). Anyhow, processes 1-8 could explain the formation of O3- radicals after oxygen exposure and subsequent UV irradiation. If there are water molecules, O3- will react with H2O.31

H2O + •O3j f OH + OH¯ + O2

(9)

Dye+•OH f degraded or mineralized products (10) 3.8. ACBK Degradation Process. The concentration changes of the ACBK (initial concentration: 10 mg/L, 50 mL) taking place in the presence of H2TPPC-TiO2 (50 mg) suspensions are illustrated in Figure 6 under exposure to incandescent lamp. Before the irradiation, the UV-vis spectrum of ACBK was

Figure 5. EPR spectrum of H2TPPC-TiO2 (a) and TNO2PP-TiO2 (b) at room temperature generated after the irradiation high-pressure mercury lamp.

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Li et al. Supporting Information Available: TGA curve for H2TPPC-TiO2 and TNO2PP-TiO2. The emission spectra of the incandescent lamp and FHPML. This material is available free of charge via the Internet at http://pubs.acs.org. References and Notes

Figure 6. Absorption spectrum of a solution of ACBK (10 mg/L, 50 mL) in the presence of H2TPPC-TiO2 (50 mg) under exposure to incandescent lamp.

characterized by one main band in the visible region with maximum absorption at 526 nm. Different structural units and groups in the dye molecules have different absorbance peaks,32 and the main conjugates of acid chrome blue K include azo linkage (-NdN-), benzene ring, and the naphthalene ring. The peak at 526 nm was attributed to the absorption of the nfπ* transition related to the -NdN- group. The adsorption diminished very fast and nearly completely disappeared after 15 min of photocatalytic oxidation, which indicated a rapid degradation of ACBK, and a complete discoloration of 10 mg/L ACBK could be achieved in 15 min with H2TPPC-TiO2 (50 mg) present. From the above-indicated results, it could be found that the discoloration of ACBK is a fast process under photocatalytic oxidation, but the destruction of the aromatic rings is difficult. This is because the lowest energy absorption band is assigned to the nfπ* transition related to the -NdN- group.33 Therefore, the •OH radical first attacks azo groups and opens -NdN- bonds, destructing the long conjugated π systems, and consequently causing discoloration. 4. Conclusions The H2TPPC-TiO2 catalyst shows high activity to degrade ACBK in aqueous solution under irradiation with an incandescent lamp. The degradation reaction process of ACBK in aqueous solution completely obeys the first-order law. Furthermore, H2TPPC-TiO2 can be precipitated without secondary pollution after reaction, and can be recovered or recycled after photocatalytic degradation. The experimental results confirmed that NSL was significantly beneficial to the photodegradation of ACBK solution in the presence of H2TPPC-TiO2, which could provide a potential approach for an energy saving application in wastewater treatment. Acknowledgment. This work was supported by the National Natural Science Foundation of China (Nos. 20631010, 20671040, and 20701033), 863 Program (No. 2006AA03Z0459), and the Program for New Century Excellent Talents in University.

(1) Sankar, M.; Sekaran, G.; Sadulla, S.; Ramasami, T. J. Chem. Technol. Biotechnol. 1999, 74, 337. (2) Fujishima, A.; Honda, K. Nature 1972, 238, 37. (3) Hoffman, M. R.; Martin, S. T.; Choi, W.; Bahnemann, D. W. Chem. ReV. 1995, 95, 69. (4) Matthews, R. W. Water. Res. 1991, 25, 1169. (5) Shen, W.; Zhao, W.; He, F.; Fang, Y. Prog. Chem. China. 1998, 10, 349. (6) Linsebigler, A. L.; Lu, G. Q.; Yates, J. T Chem. ReV. 1995, 95, 735. (7) Iwasaki, M.; Hara, M.; Kawada, H.; Tada, H.; Ito, S. J. Colloid Interface Sci. 2000, 224, 202. (8) Kamat, P. V.; Fox, M. A. Chem. Phys. Lett. 1983, 102, 379. (9) Ross, H.; Bendig, J.; Hecht, S. Sol. Energy Mater. Sol. Cells 1994, 33, 475. (10) Mele, G.; Ciccarella, G.; Vasapollo, G.; Garcı´a-Lo´pez, E.; Palmisano, L.; Schiavello, M. Appl. Catal., B 2002, 38, 309. (11) Mele, G.; Del Sole, R.; Vasapollo, G.; Garcı´a-Lo´pez, E.; Palmisano, L.; Schiavello, M. J. Catal. 2003, 217, 334. (12) Mele, G.; Del Sole, R.; Vasapollo, G.; Garcı´a-Lo´pez, E.; Palmisano, L.; Mazzetto, S. E.; Attanasi, O. A.; Filippone, P. Green Chem. 2004, 6 (12), 604. (13) Cho, S.; Li, W.; Yoon, M.; Ahn, T.; Jiang, D.; Kim, J.; Aida, T.; Kim, D. Chem.sEur. J. 2006, 12, 7576. (14) Unno, M.; Matsui, T.; Ikeda-Saito, M. Nat. Prod. Rep. 2007, 24, 553. ˆ -kawa, H.; Kojima, T. Angew. Chem., (15) Harada, R.; Matsuda, Y.; O Int. Ed. 2004, 43, 1825. (16) Imahori, H.; Hayashi, S.; Umeyama, T.; Eu, S.; Oguro, A.; Kang, S.; Matano, Y.; Shishido, T.; Ngamsinlapasathian, S.; Yoshikawa, S. Langmuir 2006, 22, 11405. (17) Hasobe, T.; Imahori, H.; Fukuzumi, S.; Kamat, P. V. J. Mater. Chem. 2003, 13, 2515. (18) Yang, X.; Dai, Z.; Miura, A.; Tamai, N. Chem. Phys. Lett. 2001, 334, 257. (19) Mele, G.; Del Sole, R.; Vasapollo, G.; Marcı`, G.; Garcı´a-Lo´pez, E.; Palmisano, L.; Coronado, J. M.; Herna´ndez-Alonso, M. D.; Malitesta, C.; Guascito, M. R. J. Phys. Chem. B 2005, 109, 12347. (20) Wang, C.; Li, J.; Mele, G.; Yang, G.; Zhang, F.; Palmisano, L.; Vasapollo, G. Appl. Catal., B 2007, 76, 218. (21) Datta-Gupta, N.; Bardos, T. J. J. Pharm. Sci. 1968, 57, 300. (22) Adler, A. D.; Longo, F. R.; Shergalis, W. J. Am. Chem. Soc. 1964, 86, 3145. (23) Rochford, J.; Chu, D.; Hagfeldt, A.; Galoppini, E. J. Am. Chem. Soc. 2007, 129, 4655. (24) Yu, J.; Chen, J.; Li, C.; Wang, X.; Zhang, B.; Ding, H. J. Phys. Chem. B 2004, 108, 2781. (25) Zhang, F.; Zhao, J.; Shen, T.; Hidaka, H.; Pelizzetti, E.; Serpone, N. Appl. Catal., B 1998, 15, 147. (26) Zhao, J.; Wu, K.; Wu, T.; Hidaka, H.; Serpone, N. J. Chem. Soc., Faraday Trans. 1998, 94, 673. (27) Zhao, J.; Wu, T.; Wu, K.; Oikawa, K.; Hidaka, H.; Serpone, N. EnViron. Sci. Technol. 1998, 32, 2394. (28) Coronado, J. M.; Maira, A. J.; Conesa, J. C.; Yeung, K. L.; Augugliaro, V.; Soria, J. Langmuir 2001, 17, 5368. (29) Meriaudeau, P.; Vedrine, J. C. J. Chem. Soc., Faraday Trans. 1976, 72, 476. (30) Anpo, M.; Kubokawa, Y.; Fujii, T.; Suzuki, S. J. Phys. Chem. 1984, 88, 2572. (31) Anpo, M. Surface Photochemistry; John Wiley & Sons: London, 1996. (32) Sun, J.; Sun, S.; Wang, G.; Qiao, L. Dyes Pigm. 2007, 74, 647. (33) Solozhenko, E. G.; Soboleva, N. M.; Goncharuk, V. V. Water Res. 1995, 29, 2206.

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