Study of the Redox Behavior of Anthraquinone in Aqueous Medium

Abstract

The electrochemical reduction mechanism of anthraquinone (AQ) has been studied in N,N-dimethyl formamide (DMF) and/or its water mixtures by means direct current polarography (DCP) and differential pulse polarography (DPP). The polarograms consisted of two well-defined waves in anhydrous DMF. The presence of small amounts of water does not effect the first wave but causes the second wave to shift toward more positive potentials; large amounts of water (solutions with at least 40% water) give a single wave. Half-wave potentials for the one-electron step in DMF are more negative than those in aqueous solutions and have been used to calculate the disproportionation constant, KD, of the radical anion in each solution. The reduction potentials in aqueous solutions have been analyzed on the basis of the Heyrovsky model. Results show that the electrode process is a two electron-two proton conversion of the AQ quinone to dihydroxyanthracene (in acidic media) or its dianion (in alkali media). From these results a reduction mechanism has been proposed for AQ in both aprotic and protic solvents. LIST OF SYMBOLS ACN acetonitrile AQanthraquinone, 9,10-dihydroxyanthracene AQ'-radical anion anthrasemiquinone AQ 2 dianion 9,10-dihydroxyanthracene AQH-anion 9,10-dihydroxyanthracene

Comparative decolorizing efficiency of textile dye by mesophilic and thermophilic anaerobic treatments

“…The decolorizing efficiencies of RB4 using acetate as co-substrate for acidogens and in treatments of methanogens (vancomycin addition) occurred by dye absorption or accumulation, as discussed previously. These indicated that the reduction of RB4, anthraqionone form to hydroquinone was related to H + generated from the organic matter conversion process, and reductive transformation of anthraquinone nucleus (Revenga et al, 1994). …”

Hydrogen production and anaerobic decolorization of wastewater containing Reactive Blue 4 by a bacterial consortium of Salmonella subterranea and Paenibacillus polymyxa

“…Thus, in the reduction process, transformation of RB4 in terms of the anthraquinone to hydroquinone was related to H ? generated from glucose degradation and reductive transformation of the anthraquinone nucleus (Revenga et al 1994). For RB4 decolorization mechanism, the results indicated evidently that acidogenesis was involved, as high decolorization efficiency, high VFAs but low methane were obtained when using glucose as compared to control and other co-substrates.…”

“…These indicated that the reduction of RB4, anthraqionone form to hydroquinone, was related with H ? , generated from organic matter conversion process, and reductive transformation of anthraquinone nucleus (Revenga et al 1994). Reducing byproduct of RB4 did not show any autooxidizing reaction, as the treated wastewater containing RB4 showed light yellow due to the unsubstituted antraquinone.…”

Reactive Blue 4 Decolorization under Mesophilic and Thermophilic Anaerobic Treatments

“…The reduction of anthraquinone dye took place by the mechanism of reversible quinone reduction to hydroquinone in two steps: benzoquinone ←→ semiquinone ←→ hydroquinone [9]. In the reduction process, transformation of RB4 in terms of the anthraquinone form to hydroquinone was related to H + generated from glucose degradation in the organic matter conversion process and reductive transformation of the anthraquinone nucleus [10]. Figure 4 shows the decolorizing efficiencies using glucose and starch as co-substrates.…”