Mechanism and Principles of Acid Red GR Degradation in the Cu²⁺/HCO₃⁻/H₂O₂ Advanced Oxidation System

To address the refractory degradation of wastewater containing the azo dye Acid Red GR, this study employed a Cu²⁺-activated HCO₃⁻/H₂O₂ （BAP） advanced oxidation system for its degradation treatment, and investigated the reaction mechanism of the system as well as the effects of various influencing factors on the degradation efficiency. The results showed that under the conditions of an initial concentration of Acid Red GR at 25 mg·L⁻¹, a concentration of HCO₃⁻ at 10 mmol·L⁻¹, a concentration of H₂O₂ at 4 mmol·L⁻¹, and a concentration of Cu²⁺ at 15 μmol·L⁻¹, the removal rate of Acid Red GR could reach over 92.7% after 20 minutes of reaction. Due to the pH being in the medium to alkaline range （6.54 ~ 10.85）, bicarbonate existed predominantly in the form of HCO₃⁻, which facilitated the generation of carbonate radicals （CO₃•⁻）; conversely, under acidic conditions （3.07 ~ 4.98）, the limited availability of HCO₃⁻ markedly suppressed the reaction rate. Common inorganic anions （H₂PO₄⁻, SO₄²⁻, Cl⁻, NO₃⁻） all had inhibitory effects to varying degrees, among which H₂PO₄⁻ had the greatest impact and NO₃⁻ had the least. Radical quenching experiments confirmed the presence of multiple reactive oxygen species in the system, among which CO₃•⁻and singlet oxygen （¹O₂） played dominant roles, while hydroxyl radicals （•OH） and superoxide radicals （O₂•⁻） participated in the reaction but made limited contributions. Electron paramagnetic resonance （EPR） spectroscopy directly confirmed the presence of •OH, CO₃•⁻, and ¹O₂.Combined with the analysis of ultraviolet-visible spectra and mass spectra, it was preliminarily inferred that the degradation of Acid Red GR mainly occured through the cleavage of the azo bond, the opening of the benzene ring, and the oxidation of the naphthalene ring. Through total organic carbon （TOC） analysis, the mineralization degree of Acid Red GR reached 49% within 30 minutes.This system achieves efficient degradation of Acid Red GR under neutral to alkaline conditions, with a wide applicable pH range and mild reaction conditions. These findings help reduce operating costs and enhancing the feasibility of practical treatment of dyeing and printing wastewater.