PHOTODEGRADATION OF EDTA AND NTA IN THE UV H2O2 PROCESS/

The influence of H2O2 on the UV degradation of the broadly used aminop olycarboxylates EDTA and NTA in aqueous solution was investigated. The photochemical degradation in the UV/H2O2 process was compared with cl assical oxidative treatment of potable water. The German drinking wate r regulation (Trinkwasserverordnung) was the orientation for all exper iments. The Advanced Oxidation Process (AOP) turned out to be superior to the classical oxidation processes. The photochemical degradation o f EDTA and NTA by UV irradiation could be significantly stimulated in the presence of H2O2. There was a strong increase in the degradation r ate and a decrease in the quantum yield of the aminopolycarboxylates. Experiments with butyl chloride as radical scavenger proved the photol ytically generated hydroxyl radicals to be responsible for the increas e in the degradation rates. The effect of increasing the degradation r ate at higher concentrations of H2O2 was limited, because the steady-s tate concentrations of the hydroxyl radicals as reactive species, did not increase at the same rate as the initial concentration of H2O2. Lo w amounts of iron dissolved from the high-grade steel photoreactor wal ls had a significant catalytic effect on the degradation.