Electrochemical Study of 2,3-Dihydroxybenzoic Acid and Its Interaction with Cu(II) and H{sub}2O{sub}2 in Aqueous Solutions: Implications for Wood Decay

摘要

The electrochemical behavior of 2,3-dihydroxybenzoic acid (2,3-DHBA) and the electron-transfer characteristics between Cu(II) and 2,3-DHBA were studied in aqueous solutions using cyclic voltammetry (CV). The overall electrochemical oxidation process of 2,3-DHBA by Cu(II) may be classified as a chemical reaction involving one-electron oxidation of 2,3-DHBA to its semiquinone radical in solution, followed by an electron-transfer reaction involving the oxidation of the semiquinone radical to a quinone at the electrode surface. In the presence of H{sub}2O{sub}2, oxidation of 2,3-DHBA by Cu(II) is enhanced due to the regeneration of Cu(II) by H{sub}2O{sub}2 oxidizing Cu(l). The redox cycling between Cu(l)/Cu(II) and H{sub}2O{sub}2 also produces hydroxyl radicals (OH{sup}-). Even though the presence of OH· may not be detected at the surface of a glassy carbon electrode, production of electroactive dissolved oxygen (O{sub}2) suggests the presence of OH· The production of O{sub}2 is dependent on Cu(II):H{sub}2O{sub}2 concentration ratio. At the electrode surface and when the initial Cu(II):H2O{sub}2 is less than 1, O{sub}2 is produced, suggesting that H{sub}2O{sub}2 may act as a scavenger for OH{sup}-; at initial Cu-(II):H{sub}2O{sub}2 > 1, the production of O{sub}2 is not favored, and OH· will be involved in the oxidation of Cu(I) and the organic ligand. The reaction mechanisms proposed in this study indicate that OH· production by chelator-mediated Fenton reactions is favorable under conditions found in the wood cell wall.