Purification of Dye Wastewater Using Bicarbonate Activated Hydrogen Peroxide: Reaction Process and Mechanisms

Advanced oxidation techniques based on H2O2 activation have recently gained lots of concern for dye wastewater treatment. A green activation approach, HCO3--H2O2 system, was employed for dye wastewater treatment in this study, and Acid Orange II (AO7) was selected as the target dye. AO7 removal performance and decomposition mechanisms were systematically explored. Almost all of the AO7 was removed within 30 min's processing. Relatively higher reaction kinetic rate constant was obtained at a relatively lower AO7 initial concentration, appropriately larger H2O2, and HCO3- dosages, and weak alkaline conditions. O-2(center dot-) was the main active substances for AO7 decomposition, and center dot OH and O-1(2) also participated in the AO7 decomposition as analyzed by different scavenger tests. The attacks of these active substances to AO7 molecules resulted in the destruction of the benzene ring, naphthalene ring, and the azo groups. Finally, the removal of chemical oxygen demand reached 72% after 60 min's oxidation treatment. The main degradation intermediates contained salicylic acid, phenol, 1,4-benzenediol, and dibutyl phthalate; and the possible decomposition pathways of AO7 in this system were proposed. Furthermore, the removal performances of different dyes in this system were all satisfactory.