Effect of Oxygen Partial Pressure and Catalysts on the Rate of UV irradiated Oxidation of EDTA

Oxidative degradation of Ethylendiamintetraacetic acid (EDTA) under UV irradiation can be carried out with oxygen absorbed from ambient air. This degradation process is a dual phase multi step process. In the first phase rapid cleavage of the substance is observed. At ambient temperature the intermediates slowly oxidize by forming carbon dioxide and water in a second phase, which is rate controlling. Oxidation of intermediates with oxygen dissolved from ambient air is controlled by the oxygen concentration, the formation of oxidizers through irradiation and the rate of oxidation. Investigation of catalytic acceleration of oxidation with heavy metal ions showed a negative impact on oxidation due to interaction of catalysts and oxidizers [KrackerSemler, 2004]. Instead of promoting the oxidation of intermediates the catalysts consumed oxidizer themselves. In a next step the role of oxygen concentration on the rate of oxidation was investigated. Partial pressure of oxygen was varied to produce an oxygen concentration in the feed solution of as much as 30 mg/l prior to irradiation. To overcome this limitation several oxidation resistant catalysts have been investigated in the ongoing project.