Characteristics of Azo Dye Decolorization in Saline Solutions by a Halotolerant Strain and Effect of Various Salts

The biodecolorization of the monoazo-sulphonic dye Acid Orange 7 (AO7) under high salinity conditions by means of Halomonas sp. WF was investigated. The results showed that a conventional substrate-inhibited model could be applied to describe the decolorization process with the concentration range from 50 to 1000 mg l-1. On the other hand, in order to study the effect of various salts that are normally present in textile waste streams, a systematic study was carried out using 10 different salt solutions. Most of the ions had no obvious effect on decolorization rate, whereas nitrate had an inhibitory effect. The rates of decolorization were found to fit to first-order kinetics. The impact of sudden salt shock during decolorization process was also examined. The final product, sulphanilic acid (SA) was characterized by LC-MS spectroscopy. The other compound resulting from AO7 breakdown, 1-amino-2-naphthol (1A2N), was not detected most likely because of its low stability.