Simultaneous hydrogen evolution and degradation of EDTA dissolved in the real wastewater over Pt/N-TiO2/SrTiO3 photocatalyst

• Main Authors: Yi-Jean Gong, 龔怡禎
• Other Authors: Ming-Yen Wey
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/00901051900872469610

碩士 === 國立中興大學 === 環境工程學系所 === 102 === Nowadays, the amount of fossil fuel on the Earth is depleting due to the development of industry. The consumption of fossil fuel accompanies the greenhouse gas emission, which causes climate change. In order to satisfy the energy demand and to restrain the negative impact on environment, developing a technology for non-pollute alternative fuel production is a necessary progress. Hydrogen, which is one of the alternative fuels, has some advantages such as high heating value and high energy conversion, so it is considered to be the major fuel for future. Among lots of hydrogen production technologies, photocatalysis is regarded as a more prospective way for hydrogen evolution because this procedure only needs solar energy, water and photocatalyst to be the major resources. After light irradiation, the photo-excited electron and hole migrated from the bulk to the surface of catalyst can facilitate the H2O reduction (H+ to H2) and organic compound oxidation), respectively. EDTA is conventionally used for the chelation of metal ions (ex: Ca, Ni, Cu, Pd, and Cd) in the manufacturing processes of electroplating industry. In the procedure of wastewater treatment, it usually need to add large amounts of heavy metal precipitant for heavy metal capture because the strong bonding between heavy metal and EDTA. If discharging wastewater into river without proper treatment, it would cause the toxic chelation compound to pollute natural water and ultimately damage the balance of ecosystem through a biologically cumulative effect. To increase the hydrogen yield and extend the application of wastewater which contained EDTA compound before treatment, the real electroplating wastewater with EDTA was chosen as the sacrificial agent for photocatalytic system, and the effect of operating variables (photocatalyst concentration, initial concentration of wastewater, reaction pH) on hydrogen evolution over Pt/N-doped TiO2/SrTiO3 triple-junction photocatalyst was investigated in this study. In addition, the photocatalytic activity of the Pt/N-doped TiO2/SrTiO3 photocatalyst was studied by photo-oxidation of EDTA molecule contained in the real electroplating wastewater. The results showed that the Pt/N-doped TiO2/SrTiO3 photocatalyst exhibited better photocatalytic activity when the photocatalyst concentration was equal to 2g L-1 under simulated sunlight irradiation, and the H2 yield reached 120 μmol/h/g. The photo-excited hole was trapped by EDTA2- and EDTA3- efficiently in the undiluted real electroplating wastewater. The Pt/N-doped TiO2/SrTiO3 photocatalyst displayed maximum photocatalytic activity (H2 yield: 305 μmol/g/h) at pH 6.0. It was ascribed to the well distribution of Pt/N-doped TiO2/SrTiO3 photocatalyst in the wastewater and the less electrostatic repulsion between Pt/N-doped TiO2/SrTiO3 photocatalyst and dissociated EDTA molecule. The results of COD analysis verified that the EDTA molecule contained in the real electroplating wastewater could be degraded by photo-excited holes in this photocatalytic system, and the best EDTA removal rate was 4476 mg/L‧h.