Photoreductive model of Disperse Orange 11 in aqueous acetone and triethylamine

The photodegradation (at lambda = 253.7 nm) of a typical anthraquinone disperse dye (DO11) in a solution containing acetone and triethylamine (TEA) has been investigated. Anthraquinone disperse dyes are known to have very low photodecay rates in the natural environment because of their low solubility. Acetone (ACE) acts not only as a solvent to increase the dye's solubility, but also as a photosensitizer to enhance the dye's photodecay rate. The photodegradation of DO11 follows pseudo first-order decay via photoreduction. In general, the decay quantum yield increases with the increase of ACE/H2O ratios and pH levels, except at very high ACE/H2O ratios or pH levels. Under these circumstances, photoreaction will be retarded because of light attenuation by excess acetone and formation of intramolecular hydrogen bonds within the dye molecules. Adding a low concentration of TEA to the aqueous acetone can further enhance the reaction because TEA can be used as an additional hydrogen source. However, an overdose of TEA will quench the reaction. The possible photoreduction mechanisms of anthraquinone disperse dye in aqueous acetone and TEA were proposed, and two models were derived that successfully described the reaction at both low and high [TEA], which made the process performance predictable.