ELECTROCHEMICAL SYNTHESIS AND PROPERTIES OF POLY(AZURE B)

A blue poly(azure B) film has been synthesized using repeated potential cycling between -0.25 and 1.10 V (versus SCE). The electrolytic solution consisted of 2.5 mmol dm(-3) azure B, 0.5 mol dm(-3) NaCl and 0.2 mol dm(-3) NaH2PO4 at the pH range of 2.0 to 11.0. The in situ visible spectrum during electrolysis of azure B shows that the intensity at 740 nm peak increases with increasing numbers of potential cycles, which is attributable to the formation of poly(azure B). The wavelength of its corresponding absorption peak is 98 nm longer than that of azure B. The polymerization rate is strongly affected by pH values. The anodic peak potential and cathodic peak potential of the poly(azure B) in a solution of pH 3.0 are not affected by increasing the scan rate from 25 to 600 mV s(-1). Poly(azure B) has good electrochemical reversibility and fast charge transfer characteristic in the pH range of 2.0 and 11.0. The conductivity of poly(azure B) is 1.5 x 10(-4) S cm(-1) According to the differences between FTIR spectra of poly(azure B) and azure B, an electrochemical polymerization mechanism of azure B is proposed in this paper.

ELECTROCHEMICAL COPOLYMERIZATION OF ANILINE AND AZURE B

The electrochemical copolymerization of aniline and N,N,N'-trimethylthionin (azure B) in aqueous solutions has been carried out using the potential sweep method. The optimum conditions for the coelectrodeposition are that the pH value and the temperature of the electrolytic solution are controlled at 5.57 and 30 degreesC, respectively, and the scan potential range is set between -0.25 and 1.10 V (versus SCE). The copolymerization rate of aniline and azure B is about 3 times larger than that of aniline in the absence of azure B. The copolymerization of aniline and azure B was verified from the results of visible spectra during electrolysis, FTIR spectra and the atomic force microscopy (AFM) images of the polymers. The in situ visible spectrum for the electrolysis of the solution containing aniline and azure B is different from that of the respective aniline and azure B. The FTIR spectrum of the copolymer is not a superposition of that of polyaniline and poly(azure B). The AFM image of the copolymer is different from those of polyaniline and poly(azure B) and is not a mixture of individual polymers. The conductivity of the copolymer synthesized at pH 5.57 is four orders of magnitude higher than that of polyaniline synthesized under the same conditions, but in the absence of azure B. The electrochemical properties of the copolymer are mainly attributed to polyaniline, but the copolymer has a better electrochemical reversibility and a much faster charge transfer than those of polyaniline.

Evaluation of Bacillus sp. MZS10 for decolorizing Azure B dye and its decolorization mechanism

To evaluate decolorization and detoxification of Azure B dye by a newly isolated Bacillus sp. MZS 10 strain, the cultivation medium and decolorization mechanism of the isolate were investigated. The decolorization was discovered to be dependent on cell density of the isolate and reached 93.55% （0.04 g/L） after 14 hr of cultivation in a 5 L stirred-tank fermenter at 2.0 g/L yeast extract and 6.0 g/L soluble starch and a small amount of mineral salts. The decolorization metabolites were identified with ultra performance liquid chromatography-tandem mass spectroscopy （UPLC-MS）. A mechanism for decolorization of Azure B was proposed as follows： the C=N in Azure B was initially reduced to -NH by nicotinamide adenine dinucleotide phosphate （NADPH）-dependent quinone dehydrogenase, and then the -NH further combined with -OH derived from glucose to form a stable and colorless compound through a dehydration reaction. The phytotoxicity was evaluated for both Azure B and its related derivatives produced by Bacillus sp. MZS 10 decolorization, indicating that the decolorization metabolites were less toxic than original dye. The decolorization efficiency and mechanism shown by Bacillus sp. MZS10 provided insight on its potential application for the bioremediation of the dye Azure B.