Photocatalytic Oxidation of Ni-EDTA in a Well-Mixed Reactor

EDTA forms a strong complex with a variety of metals. These metal-EDTA complexes are very stable and often inert to conventional biological or chemical treatment methods. Photocatalytic oxidation has shown promising results in oxidizing metal-EDTA complexes. Thus, the objective of this research was to investigate the photocatalytic oxidation of the Ni-EDTA complex. For this investigation, experiments were carried out in a semi-batch reactor equipped with up to four UV lamps (with light intensities varying from 1.6 * 10-6 to 6.4 * 10-6 einstein/min). Preliminary studies demonstrated that the photocatalytic degradation of Ni-EDTA could not take place in the absence of a source of light energy, TiO2, and oxygen. From degradation experiments, it was found that the light energy and catalyst concentration limit the production of the electron/hole pair and thus the degradation of Ni-EDTA. The effect of the initial Ni-EDTA concentration was also investigated. The results display Langmuir-Hinshelwood type kinetic behavior. A similar trend was observed when the dissolved oxygen concentration was varied. The oxygen and Ni-EDTA concentrations were also found to limit the degradation of Ni-EDTA. In all experiments, the total organic carbon (TOC) measurements showed that minimal mineralization of the starting Ni-EDTA took place.