Photocatalytic degradation of bisphenol A in a visible light/TiO2 system

doi:10.1016/j.desal.2010.02.020

Desalination

Volume 256, Issues 1–3, June 2010, Pages 37-42

https://doi.org/10.1016/j.desal.2010.02.020 Get rights and content

Abstract

This study evaluates the photodegradation efficiency of bisphenol A (BPA) in a visible light/TiO₂ system. TiO₂ was generated by the sol–gel method and polyethyleneglycol (PEG) was used as a modulator. The effects of the molecular weight of PEG, the addition percentage of PEG, the pH of the solution and the TiO₂ dose were determined. For a given percentage of PEG added, the intensity of anatase followed the order TiO₂/PEG600 > TiO₂/PEG3500 > TiO₂/PEG200. The BPA degradation rates of visible light/TiO₂/PEG200 (10%), visible light/TiO₂/PEG600 (5%) and visible light/TiO₂/PEG3500 (0.5%) at pH 4 were 2.07, 3.01 and 2.90 h^− 1, respectively. After 12 h of reaction, the reductions of TOC in visible light/TiO₂, visible light/TiO₂/PEG200 (10%), visible light/TiO₂/PEG600 (5%) and visible light/TiO₂/PEG3500 (0.5%) systems were 38%, 56%, 65% and 64%, respectively. The concentrations of hydroxyl radicals in visible light/TiO₂, visible light/TiO₂/PEG200 (10%), visible light/TiO₂/PEG600 (5%) and visible light/TiO₂/PEG3500 (0.5%) systems were determined to be 50.1, 88.6, 78.8 and 75.1 μM, respectively. This study finds that adding PEG during the preparation of TiO₂ increased the photoactivity of the generated TiO₂ however, the optimal PEG addition percentage varied with the molecular weight of PEG.

Introduction

Bisphenol A (BPA), a suspected endocrine disrupting compound (EDC), is widely adopted in the production of epoxy resins and polycarbonate plastics, which are used in various food and drink packaging applications, baby bottles and dental sealants [1]. The extensive use of BPA has attracted considerable attention from regulatory agencies and scientists. The removal of BPA from wastewater is regarded as important to environmental protection. BPA is an antioxidant that is non-biodegradable and highly resistant to chemical degradation, and presents a health risk to both humans and animals. Consequently, because of the wide range of applications of BPA, exposure to which is a serious concern and a health hazard, researchers must develop effective remediation procedures for destroying BPA in contaminated effluent.

Various methods for removing BPA from wastewater have been suggested. They include adsorption [2], UV [3], [4], [5], UV/O₃ [4], UV/H₂O₂ [3], [5], [6], Fenton [7], sono-Fenton [7], UV/Fenton [8] and UV/TiO₂ [9], [10], [11], [12], [13], [14]. Rosenfeldt and Linden [3] studied the degradability of BPA by direct photolysis using low- and medium-pressure mercury UV lamps, finding 5% and 10–25% degradations, respectively. Moreover, the exposure of the same samples to UV/H₂O₂ eliminated more than 90% BPA, independently of the UV source. Katsumata et al. [8] found that the destruction of BPA was maximal at pH = 3.5–4.0 with an H₂O₂:Fe(II) ratio of ten under UV (λ < 300 nm) irradiation, under which conditions 50% mineralization occurred in 24 h. The degradation of BPA by the Fenton process was much more rapid in the presence of ultrasound than in its absence [7]. In previous studies, TiO₂ was the most commonly used catalyst in the treatment of wastewater because of its non-toxicity, reasonable cost, high availability, photochemical stability and relatively high photocatalytic activity [9], [10], [11], [12], [13], [14]. Coleman et al. [12] found that adding silver or platinum did not affect photocatalytic degradation or mineralization by UV/TiO₂ for any of the EDCs at concentrations present in water. At a high concentration of BPA, a significant increase in the reaction rate was observed over Pt/TiO₂. However, the reaction rate of BPA was reduced over Ag/TiO₂. Variations in the experimental conditions are the main cause of variations in the final outputs and conclusions of those studies. Therefore, no universal explanation of the effects of photocatalysis of organics in water is available, and several factors should be considered. UVB and UVC are commonly applied light sources in the photocatalytic degradation of BPA. Visible light/TiO₂ has seldom been used to degrade BPA and accordingly, further research on the photodegradation of BPA by visible light/TiO₂ must be performed.

This study employs the sol–gel method to generate TiO₂; polyethyleneglycol (PEG) was used as the modulator. BPA was the model compound. This study attempts the following; to (i) identify the characteristics of the sol–gel-produced TiO₂ with the addition of different proportions of PEG; (ii) evaluate the effects of the molecular weight and addition percentage of PEG on the photocatalytic activity of the produced TiO₂; (iii) determine the effects of pH and the TiO₂ dosage in visible light/TiO₂ to degrade BPA and (iv) compare the mineralization performance of BPA with the various sol–gel-produced TiO₂ compounds under 410 nm irradiation.

Section snippets

Materials

Parent compound BPA was obtained from Aldrich (purity > 99%) and used as received. Three PEGs were adopted as modulators in the preparation of TiO₂. The molecular weights of PEG were 200, 600 and 3500 g/mol (Merck). Titanium (IV) ethoxide (Ti(OC₂H₅)₄) (Merck) was used as the source of Ti. The pH of the solution was controlled by adding HClO₄ and NaOH using an automatic titrator. Salicylic acid, 2, 3-dihydroxybenzoic acid (2, 3-DHBA), 2, 5-dihydroxybenzoic acid (2, 5-DHBA) and catechol (Acros) were

Characteristics of produced TiO₂

Fig. 1 presents the TEM images of TiO₂ with different PEG ratios. The diameter of TiO₂/PEG600 ranged from 10 to 30 nm, independently of the PEG600 addition ratio. In PEG/catalyst systems, PEG acts as a surfactant stabilizer, suppresses coagulation and increases the homogeneity of the final product. The TiO₂ powder that is prepared without adding PEG is non-uniform, while that prepared by adding PEG to the sol is uniform and has a granular texture (Fig. 1). Notably, increasing the PEG addition

Conclusions

This study adopted the sol–gel procedure to generate TiO₂; PEG was used as the modulator. The photoactivity of the formed TiO₂ was evaluated from its capacity to photodegrade BPA. The experimental results demonstrate that a higher PEG molecular weight and a higher addition percentage were associated with a larger surface area of the produced TiO₂. The BPA degradation rates in the visible light/TiO₂ system followed the order pH 4 > pH 7 > pH 10. This study suggests that adding PEG to the TiO₂

Acknowledgements

The authors would like to thank Ms. Hsieh for helping some experiments and the National Science Council of the Republic of China for financially supporting this research under Contract No. NSC 98-2221-E-224-002.

References (29)

C.A. Staples et al.
Chemosphere
(1998)
C.Y. Kuo
Desalination
(2009)
S. Irmak et al.
Journal of Hazardous Materials
(2005)
P.J. Chen et al.
Chemosphere
(2006)
M. Neamtu et al.
Water Research
(2006)
I. Ioan et al.
Journal of Hazardous Materials
(2007)
H. Katsumata et al.
Journal of Photochemistry and Photobiology A
(2004)
N. Watanabe et al.
Chemosphere
(2003)
K. Chiang et al.
Applied Catalysis A
(2004)
T. Kanki et al.
Chemical Engineering Journal
(2005)

H.M. Coleman et al.

Chemical Engineering Journal

(2005)

N. Venkatachalam et al.

Catalysis Communications

(2007)

R. Wang et al.

Journal of Hazardous Materials

(2009)

R.S. Sonawane et al.

Materials Chemistry and Physics

(2004)

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Photocatalytic degradation of bisphenol A in a visible light/TiO2 system

Abstract

Introduction

Section snippets

Materials

Characteristics of produced TiO2

Conclusions

Acknowledgements

Chemosphere

Desalination

Journal of Hazardous Materials

Chemosphere

Water Research

Journal of Hazardous Materials

Journal of Photochemistry and Photobiology A

Chemosphere

Applied Catalysis A

Chemical Engineering Journal

Chemical Engineering Journal

Catalysis Communications

Journal of Hazardous Materials

Materials Chemistry and Physics

Photocatalytic degradation of bisphenol A in a visible light/TiO₂ system

Characteristics of produced TiO₂