(63f) Photochemical And Electrochemical Oxidation Of Ethylenediaminetetraacetic Acid (Edta)

Photochemical and electrochemical Advanced Oxidation Processes (AOP/EAOP) are efficient oxidation operations for degradation of persistent pollutants such as pesticides, substituted aromatic hydrocarbons, dyes and complexing agents. The UV/H2O2 -, UV/O3- processes and the Fenton process are representative photochemical AOPs. Anodic oxidation is an electrochemical AOP. Both technological groups generate reactive hydroxyl radicals (E°=2,80 V), which mineralize contaminants or at least convert pollutants into less toxic or biodegradable products.

The aim of the project was a comparison of approved photochemical processes and electrochemical processes. Criterion for comparison was the potential of degradation and mineralization, as well as the specific energy consumption. EDTA (ethylenediaminetetraacetic acid) was used as model substance. EDTA is classified as persistent. All experiments were carried out with a start concentration of 1,34 mM Na2EDTA. Photochemical degradation was carried out in a UV-reactor system, type Heareus Noblelight UV-RS-2, equipped with a 15 W mercury low-pressure lamp. Electrochemical degradation was performed in open cell electrolysis with different electrode materials and 0.05 M Na2SO4 for conductivity. The processes UV/Fe(II) and UV/H2O2 show a similar degradation rate of EDTA. Mineralization was quantified by determination of the TOC-value and EDTA degradation was determined by HPLC analysis.