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Photocatalytic Reduction of Nitrate on Metal Modified TiO2

Author: TangJing
Tutor: ZhaoWeiRong
School: Zhejiang University
Course: Environmental Engineering
Keywords: Silver Photocatalytic Reduction Metal loading Nitrate Electrochemical Properties
CLC: X703
Type: Master's thesis
Year: 2012
Downloads: 31
Quote: 0
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Abstract


Nitrate is an important part in the total nitrogen removal of outside sources, ammonia, nitrite can also be converted to nitrate. Therefore, not only by the effective processing technology to reduce the nitrate content, but also further to control the selectivity of the nitrate reduction products, so that it translates into no environmental impact of nitrogen, thereby reducing the total nitrogen content in water, and ultimately achieve repair contaminated The purpose of the water body. To P25 as the carrier, using photoreduction Ti02 catalyst prepared modified amount of different metal ions, metal ion species including the noble metal palladium (Pd), ruthenium (Ru), silver (Ag), and a transition metal (Fe). Investigated in formic acid as a hole-trapping agent, to restore the initial concentration of the catalyst under 365nm UV irradiation 30mgN / L of nitrates effects and selectivity for nitrogen. Preliminary studies indicate that the same modification amount under the same reaction conditions, a variety of metals of Ag-TiO2 catalyst in a 365nm wavelength for nitrate reduction effect Preferably, on this basis investigated Ag loading, catalyst dosage kind of hole-trapping agent, formic acid concentration, reaction time, pH, and the gases pass into the influence of the factors on the reduction of nitrate (nitrate conversion rate generate nitrite nitrogen, ammonia concentration, and a nitrogen-selective). It was found that the loading of 5.0wt%, the dosage of 0.1g of Ag-TiO2 catalyst in the hole trapping agent 0.03mol / L formic acid reaction 6h photocatalytic reduction of nitrate effect. In this case, the nitrate nitrogen conversion rate reached 90%; nitrite generated concentration was lower, the ammonia generation rate of about 10%, the nitrogen selectivity of 90% or more. Nitrate reduction effect of the Ag-TiO2 catalyst under visible light irradiation experiments were carried out under the best experimental conditions. The results showed that nitrogen selectivity for nitrate reduction rate was about 12%, 79%. Load photoreduction prepared 5.0wt% Ag-TiO2 catalysts were characterized by XRD, XPS, UV-vis and electrochemical techniques. XRD results indicate that the Ag-TiO2 catalyst is anatase Ag loading of the particle diameter of the catalyst no significant effect, are about 20nm. UV-vis results show that, compared with P25, an Ag-TiO2 catalyst absorption sidebands occur redshift Ag loading conducive to the absorption of visible light photocatalyst. Load change catalyst light response. XPS results show that the load of Ag mainly exists in the form of metallic silver. By cyclic voltammetry, linear sweep voltammetry, Tafel polarization and electrochemical means to study electron transfer behavior of Ag-TiO2 catalyst photocatalytic process and initial nitrate concentration for the electrochemical behavior of the results that with increasing nitrate concentration, the carrier concentration is increased to accelerate the electron transfer to nitrate reduction reaction is also accelerated.

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CLC: > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization
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