Mineralization and toxicity reduction of textile dye neutral red in aqueous phase using BiOCl photocatalysis.

The BiOCl catalyst was prepared by hydrolysis method. The compound was extensively characterized by XRD, SEM, TEM, UV-vis measurements and BET surface area. The prepared material had average pore diameter about 6-13 nm. The BET surface area of the sample is about 40 m(2)/g. The photocatalytic degradation and toxicity reduction of textile dye neutral red (NR) was investigated in the presence of as prepared BiOCl. The analysis of (·)OH radical formation was performed by fluorescence technique. The intermediates and the final products of degradation were detected by high-performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry (HPLC-ESI-DAD-MS) technology. Decrease in chemical oxygen demand (COD) and dye absorbance of the photodegraded dye solution revealed a complete mineralization of NR into CO(2) and inorganic ions. The recycling experiments confirmed the relative stability of the catalyst. Finally, the luminescent marine bacteria Vibrio fischeri was used to assess the acute toxicity of samples prior to and after the photocatalytic treatment and it was found that toxicity was fully eliminated following photocatalytic degradation.

Oxidation of toluidine blue by chlorite in acid and mechanisms of the uncatalyzed and Ru(III)-catalyzed reactions: a kinetic approach.

The complex mechanism of the uncatalyzed and Ru(III)-catalyzed oxidation of toluidine blue [(7-amino-8-methylphenothiazin-3-ylidene)dimethyl ammonium chloride, TB(+)Cl(-)] (λ(max) = 626 nm) by acidic chlorite is elucidated by a kinetic approach. Both the uncatalyzed and catalyzed reactions had a first-order dependence on the initial ClO(2)(-) and H(+) concentrations ([ClO(2)(-)](0) and [H(+)](0), respectively). The catalyzed reaction had a first-order dependence on the initial Ru(III) concentration ([Ru(III)](0)). The overall reaction of toluidine blue and chlorite ion was as follows: TB(+) + 5ClO(2)(-) + H(+) = P + 2ClO(2) + 2HCOOH + 3Cl(-) + H(2)O, where P is (7-amino-8-methyl-5-sulfoxophenothiazin-3-ylidene)amine. Consistent with the experimental results, the pertinent reaction mechanisms are proposed.