Degradation of EDTA in H2O2 -containing wastewater by photo-electrochemical peroxidation

Abstract Semiconductor wastewater currently contains H 2 O 2 which is an important reagent in wafers cleaning. Recalcitrant organic pollutant such as EDTA are always present in this type of wastewater and may represent a threat for the environment. In this work, a new photoelectrochemical reactor is proposed to remove EDTA from H 2 O 2 contaning wastewater. First, photolysis, electrochemical peroxidation and photo-electrochemical peroxidation were compared. The results showed that the removal efficiency decreases in the sequence: UV/H 2 O 2 «EC/H 2 O 2 2 O 2 . The main parameters affecting the photo-electrochemical peroxidation process were studied. The study revealed that the optimal current was 50 mA, while the optimum initial pH was found in the acidic range from 2.25 to 3.0, with a peak at 2.25. Increasing H 2 O 2 concentration results in increasing in EDTA removal up to 92.1%, while decreasing initial EDTA concentration up to 22.5 mg L −1 gives a complete removal in only 90 min. It was also found that the degradation of EDTA greatly depends on the nature of the present cation.