Degradation of EDTA in H_2O_2 -containing wastewater by photo-electrochemical peroxidation

摘要

Semiconductor wastewater currently contains H2O2which 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 H2O2contaning wastewater. First, photolysis, electrochemical peroxidation and photo-electrochemical peroxidation were compared. The results showed that the removal efficiency decreases in the sequence: UV/H2O2«EC/H2O22O2. 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 H2O2concentration results in increasing in EDTA removal up to 92.1%, while decreasing initial EDTA concentration up to 22.5 mg L−1gives 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.