[Stimulation of biodecolorization of direct yellow 11 by decolorization products of reactive black 5].

This study focused on the effects of decolorization products of reactive black 5 (RB5) on anaerobic decolorization of direct yellow 11 (DY11) by Rhodopseudomonas palustris W1 and its reaction mechanisms. The results showed that the decolorization products of RB5 could obviously accelerate biological decolorization rate of DY11. For initial concentration of 200 mg/L of DY11, the addition of decolorization products of RB5 resulted in that the decolorization kinetic constant K was increased from 17 mg/(L x h) to 42.5 mg/(L x h), followed by an further increase to 48.8 mg/(L x h) after optimization of RB5 supplement. Cyclic voltammogram analysis demonstrated that the decolorization products of RB5 presented electrochemical activity due to the presence of redox electron transfer mediators, as indicated by an observation of two current peaks of reversible oxidation and reduction appeared at potential of ca. 83 mV and -200 mV, respectively. According to LC-MS and FT-IR analysis, the electrochemically activated species of the decolorization products were characterized to be 7-amino-8-hydroxy-1, 2-naphthaquinone-3, 6-disulphonate-1, 2-diimine (TAHNDSDP-1). TAHNDSDP-1 with quinine-like structure was able to transfer between its oxidative and reductive forms by transferring 2[H], which was supposed to be the redox mediator to shuttle electrons from electron donors to azo dyes, thus, improving the reduction of de materials.