| Bisphenol A (BPA) is one of the representative endocrine disrupting chemicals (EDCs), which does some harm to the endocrine and reproductive system of animals and human. The largely producing and wide use of BPA lead to the release of BPA into environment. In some environmental medium, such as atmosphere and water, BPA has been monitored. In view of this, seeking an effective treatment method for BPA is of great importance and urgency. TiO2 photoelectrocatalytic (PEC) method is a high-efficient advanced oxidative technology and has been commonly applied to treat various organic pollutants. It has some advantages such as high degrading and mineralizing efficiency and no secondary pollution. This paper studied the removal of BPA by TiO2 nanotube arrays photoelectrocatalytic technology.To extend the photoresponse range of TiO2 nanotube arrays (TNAs) which prepared by anodizationg method, Fe3+was loaded through dip-coating method (Fe/TNAs). The samples were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectrum, X-ray diffractometer and UV-Vis diffuse reflectance spectroscopy. Results indicated that the doping of Fe3+didn’t change the microtopography of TNAs, but made the light absorbing edge red-shift and enhanced its absorption in visible region.PEC degradation of BPA using Fe/TNAs as the photoanode, Ti foil as the cathode, xenon light as simultaneous solar-light source was studied. Experimental results showed that the increase of Fe3+doping amout and current density and aeration favored the removal of BPA. After 240 min treatment, 72.3% of BPA (initial concentration of 10 mg/L) could be degraded, indicating that Fe/TNAs PEC was an effective method for BPA treatment. Under the same conditions, air was pumped into reaction solution with airflow rate of 1.0 L/min during reaction. The removal rate reached 82.7%, which indicated that aeration was an effective means to boost the efficiency of photoelectrocatalysis.In addition, the BPA degraded by aeration assisted PEC process was investigated. In this system, the cathode was carbon-cloth and air was pumped into reaction solution continueously during reaction. Factors that influence the removal rate, such as Fe3+doping amout, current density, pH, airflow rate and initial BPA concentration were evaluated. The results showed that under the conditions that Fe/TNA-5 as the photoanode, current density of 1.25 mA/cm, pH of 3, initial BPA concentration of 10 mg/L and airflow rate of 0.5 L/min, BPA removal rate reached 91.1% after 240 min reaction and mineralization rate reached 73% after 360 min reaction.The mechanisms of BPA degradation by aeration assisted PEC was also disscussed. Determination of H2O2 concentration in reaction solution with or without BPA demonstrated there was H2O2 generated in the system and participated in the BPA degradation. The comparasion tests by adding different radical scavengers indicated that photogenerated holes didn’t paritcipate in reaction directly, O2·- and ·OH were the main radicals to degrade BPA. In addition, O2·- not only acted as the intermediate for producing reactive oxygen species (such as ·OH) but also degraded BPA directly. |
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