published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

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Metal-Ethylenediaminetetraacetic acid (EDTA) complexes are found in a variety of industrial process. The stability of the formed complexes makes these compounds often inert to conventional wastewater treatment systems. In this work, the photocatalytic oxidation of NiEDTA was investigated as a means of breaking up the chelated nickel. The studied variables included the light intensity rate, the catalyst (TiO2), oxygen and NiEDTA concentrations. Photocatalytic experiments showed that increasing the catalyst concentration (0.5-3.0 g/L) decreases the light penetration inside the reactor resulting in a decrease in the reaction rate. The effect of oxygen and NiEDTA concentration was shown to exhibit Langmuir-Hinshelwood type kinetics. Total organic carbon (TOC) did not show any significant mineralization of NiEDTA for all investigated conditions. As a result, the by-products of the reaction were measured and found to include ED3A (ethylenediaminetriacetic acid), N-N'-EDDA (ethylenediamindiaacetic acid), IDA (iminodiacetic acid), oxalic acid, oxamic acid, glyoxylic acid, formaldehyde, ammonia, nitrate and nitrite. ED3A was found to be the major by-product of the reaction and nitrogen added from NiEDTA was found to be released as ammonia nitrogen. Oxygen consumption experiments were demonstrated as an effective way to monitor the rate of the reaction through measurement of the electron oxygen utilization rate. Nickel precipitation experiments showed that some of the by-products of NiEDTA degradation formed complexes with nickel. Finally, a light distribution model was generated using a CFD software (Fluent 6.1.22). For the catalyst concentration range of 0.5 to 3.0 g/L, this model showed that all of the light energy supplied by a centered UV lamp is absorbed within a one centimeter distance. Using the local volumetric rate of energy absorption (LVREA) calculated from the model the rate of the reaction was expressed in terms of quantum yield. For experiments carried out with air the quantum yield showed that the degradation rate was limited from an insufficient oxygen supply for electron scavenging. Increasing the oxygen concentration to 0.60 mmole O2/L increased the quantum yield for the highest light intensity rate; however the quantum yield never reached an optimum value thus indicating that other limiting conditions exist.

No description available.

No description available.

No description available.

No description available.

No description available.