Degradação fotoeletroquímica de corantes dispersos em efluente têxtil utilizando fotoanodos de Ti/TiO2

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Amorphous manganese polyphosphates: preparation, characterization and incorporation of azo dyes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mutagenic compounds generated from the chlorination of disperse azo-dyes and their presence in drinking water

The water produced by the Cristais River Drinking Water Treatment Plant (CR-DWTP) repeatedly produced mutagenic responses that could not be explained by the presence of disinfection byproducts (DBPs) generated by the reaction of humic acids and chlorine. In order to determine the possible role of chlorinated dye products in this mutagenic activity, solutions of a black dye commercial product (BDCP) composed of C. I. Disperse Blue 373, C. I. Disperse Orange 37, C. I. Disperse Violet 93, and chemically reduced BDCP (R-BDCP) were chlorinated in a manner similar to that used by the CR-DWTP. The resulting solutions were extracted with XAD-4 along with one drinking water sample collected from the CR-DWTP. All extracts showed mutagenic activity in the Salmonella/microsome assay. Dye components of the BDCP as well as its reduced chlorinated (Cl-R-BDCP) derivative were detected in the drinking water sample by analysis with a high performance liquid chromatography/diode array detector (HPLC/DAD). The mutagenicity results of these products suggest that they are, at least in part, accounting for the mutagenic activity detected in the drinking water samples from the Cristais River. The data obtained in this study have environmental and health implications because the chlorination of the BDCP and the R-BDCP leads to the formation of mutagenic compounds (Cl-BDCP and Cl-R-BDCP), which are potentially important disinfection byproducts that can contaminate the drinking water as well as the environment.

Oil-soluble dyes for marking Spodoptera frugiperda (Lepidoptera : Noctuidae)

Although various biological aspects of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) have been examined, adult movement and dispersal of this insect pest is not well understood. Release-recapture techniques by using marked insects is a useful approach for dispersal studies; however, the marking technique should not significantly affect insect biology or behavior. Therefore, the effect of different concentrations of oil-soluble dyes (Solvent Blue 35 [C.I. 61554], Sudan Red 7B [C.I. 26050], Sudan Black B [26150], Sudan Orange G [C.I. 11920], and Sudan I 103624 [C.I. 12055]) on development, mortality, and fecundity of S. frugiperda was evaluated. Dyes were added to artificial diet used to feed larvae. Larval and pupal development and mortality, adult longevity, and female fecundity were evaluated. High concentrations (400 and 600 ppm) of all dyes led to longer larval and pupal stages. Adult life span and number of eggs were not affected by the dyes. Sudan Red 7B marked both adults and eggs very well. Solvent Blue 35 marked both adults and eggs, but the blue-marked eggs could not be distinguished from some bluish eggs laid by nonlabeled females. Adults and eggs were not adequately marked by the Sudan Black B, Sudan Orange G, and Sudan I 103624 (a yellow dye).

Evaluation of different electrochemical methods on the oxidation and degradation of Reactive Blue 4 in aqueous solution

The oxidation of a reactive dye, Reactive Blue 4, RB4, (C.I. 61205), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode and reticulated vitreous carbon electrode occurs in only one step at 2.0 < PH < 12 involving a two-electron transfer to the amine group leading to the imide derivative. Dye solution was not decolorized effectively in this electrolysis process. Nevertheless, the oxidation of this dye on Ti/SnO2/SbOx (3% mol)/RuO2 (1% mol) electrode showed 100% of decolorization and 60% of total organic carbon removal in Na2SO4 0.2 M at PH 2.2 and potential of +2.4 V. Experiments on degradation photoelectrocatalytic were also carried out for RB4 degradation in Na2SO4 0.1 K PH 12, using a Ti/TiO2 photoanode biased at +1.0 V and UV light. After 1 h of electrolysis the results indicated total color removal and 37% of mineralization. (c) 2004 Elsevier Ltd. All rights reserved.

Electrochemical reduction and determination of Cibacron Blue F3GA at poly-L-lysine modified glassy carbon electrode

The oxidation of a reactive dye, Cibacron Blue F3GA, CB, (C.I. 61211), widely used in the textile industries to color natural fibers, was studied by electrochemical techniques. The oxidation on glassy carbon electrode occurs in two steps at 2.0 < pH < 10 involving one electron transfer each to the amine group leading to the imide derivative. Stable films of poly-L-lysine (PLL) in the presence of glutaraldehyde (GA) 97.5%:2.5% on glassy carbon electrode can be used to detect low levels of dye using its oxidation peak at +0.75V by voltammetry. Linear calibration graphs were obtained for the CB reactive dye, from 1.0 X 10(-6) to 1.0 X 10(-5) mol L-1 in B-R buffer, pH 2.0, using a pre-concentration off-line during 10 min. The detection limit (3 sigma/slope) was calculated to be 4.5 X 10(-8) mol L-1. Films of PLL can readily be applied for the determination of CB dye bearing aminoanthraquinone as chromophore and chlorotriazinyl as reactive group at concentrations at least 100 times lesser than using a glassy carbon electrode without modification. The method described was applied for the determination of CB dye in tap water and raw water collected from the municipal treatment plant with a recovery of 89.2% +/- 5.4 and 88.0% +/- 6.5, respectively. (c) 2005 Elsevier Ltd. All rights reserved.

Evaluation of color removal and degradation of a reactive textile azo dye on nanoporous TiO2 thin-film electrodes

The feasibility of the photobleaching of a textile azo dye, reactive orange 16 (C.I. 17757), in aqueous solution using titanium dioxide thin-film electrodes prepared by the sol-gel method was investigated. The best conditions for maximum photoelectrocatalytic degradation were found to be pH > 10 for Na2SO4 medium and pH < 6 for NaCl. In both situations, an applied potential of +1.0 V and low dye concentration are recommended, when 100% of color removal is obtained after 20 min of photoelectrocatalysis. The effects of side reaction pathway on the degradation rate of dye in sulfate and chloride medium were presented and the best performance are optimized to situations closed to that verified in the textile effluent. The influence of variables as applied potential, pH, supporting electrolyte and dye concentration on the kinetics of photoelectrochemical degradation also were investigated. Oxalic acid is identified by HPLC and UV-Vis spectrophotometric methods as the main degradation product generated after 180 min of photoelectrocatalysis of 4 x 10(-5) mol l(-1) dye in sodium sulphate pH 12 and NaCl pH 4.0 and a maximum reduction of 56 and 62% TOC was obtained, respectively. (C) 2004 Elsevier Ltd. All rights reserved.

Degradation of Acid Blue 40 dye solution and dye house wastewater from textile industry by photo-assisted electrochemical process

In this paper, electrochemical and photo-assisted electrochemical processes are used for color, total organic carbon (TOC) and chemical oxygen demand (COD) degradation of one of the most abundant and strongly colored industrial wastewaters, which results from the dyeing of fibers and fabrics in the textile industry. The experiments were carried out in an 18L pilot-scale tubular low reactor with 70% TiO2/30% RuO2 DSA. A synthetic acid blue 40 solution and real dye house wastewater, containing the same dye, were used for the experiments. By using current density of 80 mA cm(-2) electrochemical process has the capability to remove 80% of color, 46% of TOC and 69% of COD. When used the photochemical process with 4.6 mW cm(-2) of 254nm UV-C radiation to assist the electrolysis, has been obtained 90% of color, 64% of TOC and 60% of COD removal in 90 minutes of processing; furthermore, 70% of initial color was degraded within the first 15 minutes. Experimental runs using dye house wastewater resulted in 78% of color, 26% of TOC and 49% of COD in electrolysis at 80 mA cm(-2) and 90 min; additionally, when photo-assisted, electrolysis resulted in removals of 85% of color, 42% of TOC and 58% of COD. For the operational conditions used in this study, color, TOC and COD showed pseudo-first-order decaying profiles. Apparent rate constants for degradation of TOC and COD were improved by one order of magnitude when the photo-electrochemical process was used.

Studies of the voltammetric behavior and determination of diazo reactive dyes at mercury electrode

The electrochemical reduction of two reactive dyes: Procion Red HE-3B 9 (RR120) and Procion Green HE-4BD (RG19) was investigated using cyclic voltammetry, differential pulse and DC, polarography, chronoamperometry and controlled potential electrolysis at mercury electrodes. The bis-azo groups of the RR120 dye are reduced together in one single step of four electrons, the bis-azo groups of the RG19 dye are reduced in two steps owing to the difference in the electron densities promoted by the different substituents in the benzene rings adjacent to the azo groups. The bis-monochlorotriazine reactive groups in both dyes are reduced only in acidic medium in their protonated form, leading to the reduction of the triazine groups. The reduction mechanism of both reactive dyes is discussed. Both dyes can be quantified in aqueous medium by differential pulse polarography in the concentration range of 1 x 10(-7) mol L-1 to 1 x 10(-5) mol L-1 by monitoring the reduction of the chromophore group or the reactive group.

Analysis of aromatic amines in surface waters receiving wastewater from a textile industry by liquid chromatographic with electrochemical detection

A high performance liquid chromatography ( HPLC) method with electrochemical detection (ED) was developed for the determination of benzidine, 3,3-dimethylbenzidine, o-toluidine and 3,3-dichlorobenzidine in the wastewater of the textile industry. The aromatic amines were eluted on a reversed phase column Shimadzu Shimpack C-18 using acetonitrile + ammonium acetate (1 x 10(-4) mol L-1) at a ratio 46: 54 v/v as mobile phase, pumped at a flow rate of 1.0 mL min(-1). The electrochemical oxidation of the aromatic amines exhibits well-defined peaks at a potential range of +0.45 to +0.78 V on a glassy carbon electrode. Optimum working potentials for amperometric detection were from 0.70 V to +1.0 V vs. Ag/AgCl. Analytical curves for all the aromatic amines studied using the best experimental conditions present linear relationship from 1 x 10(-8) mol L-1 to 1.5 x 10(-5) mol L-1, r = 0.99965, n = 15. Detection limits of 4.5 nM (benzidine), 1.94 nM (o-toluidine), 7.69 nM (3,3-dimethylbenzidine), and 5.15 nM (3,3-dichlorobenzidine) were achieved, respectively. The detection limits were around 10 times lower than that verified for HPLC with ultra violet detection. The applicability of the method was demonstrated by the determination of benzidine in wastewater from the textile industry dealing with an azo dye processing plant.

Assessment of the application of cathodic stripping voltammetry to the analysis of diazo reactive dyes and their hydrolysis products

Two reactive dyes, C.I. Reactive Red 120 (RR120) and C.I. Reactive Green 19 (RG19), each bearing two azo groups as the chromophoric moiety and two monochloro-s-triazine groups as reactive groups, can be detected at nanomolar levels using cathodic stripping voltammetry. Linear calibration graphs were obtained for both reactive dyes, from 0.015 to 0.14 mu mol l(-1) for RR120 in pH 4 buffer and from 0.012 to 0.26 mu mol l(-1) for RG19 in pH 3 buffer, using a preconcentration at 0 V during 180 and 240 s on the mercury electrode, respectively. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Electrochemical reduction of azo-based chlorotriazine reactive dyes

The reduction process of the azo dyes reactive red 120 and reactive green 19 was investigated in B-R buffer pH 2-12 by differential pulse polarography, cyclic voltammetry and controlled potential electrolyse. The reactive red 120 presents two azo groups reducible in a single step of 8 electrons followed by simultaneous reduction of the two clorotriazine groups. The reduction of reactive green 19 is complicated by the presence of azo groups and chlorotriazine moyeties in a non symmetrical molecule. The peaks can be monitored for dyes determination in concentration level up to 1x10(-7) mol/L and 1x10(-9) mol/L using differential pulse polarography or cathodic stripping voltammetry.

Trajectory of Water- and Fat-Soluble Dyes in the Grass-Cutting ant Atta capiguara (Hymenoptera, Formicidae): Evaluation of Infrabuccal Cavity, Post-Pharyngeal Glands and Gaster

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The effect of endodontic materials on the optical density of dyes used in marginal leakage studies

The aim of this study was to determine the effect of the exposure of different endodontic materials to different dye solutions by evaluating the optical density of the dye solutions. Seventy-five plastic tubes were filled with one of the following materials: AH Plus, Sealapex, Portland cement, MTA (Angelus and Pro Root) and fifteen control plastic tubes were not. Each specimen of material and control was immersed in a container with 1 ml of each dye solution. A 0.1 ml-dye solution aliquote was removed before immersion and after 12, 24, 48 and 72 hours of each specimen immersion to record its optical density (OD) in a spectrophotometer. Statistical analysis was performed with ANOVA and Tukey tests (5%). No significant difference was found among any of the solution OD values for AH Plus cement. Portland cement promoted different OD values after 12 hours of immersion. MTA-Angelus cement presented different OD values only for 2% rhodamine B and the MTA-Pro Root cement presented different OD values in all 2% rhodamine B samples. Sealapex cement promoted a reduction in the India Ink OD values. Dye evaluation through OD seems to be an interesting method to select the best dye solution to use in a given marginal leakage study.

Heterogeneous photocatalytic treatment of organic dyes in air and aqueous media

This review focuses on the heterogeneous photocatalytic treatment of organic dyes in air and water. Representative studies spanning approximately three decades are included in this review. These studies have mostly used titanium dioxide (TiO2) as the inorganic semiconductor photocatalyst of choice for decolorizing and decomposing the organic dye to mineralized products. Other semiconductors such as ZnO, CdS, WO3, and Fe2O3 have also been used, albeit to a much smaller extent. The topics covered include historical aspects, dark adsorption of the dye on the semiconductor surface and its role in the subsequent photoreaction, semiconductor preparation details, photoreactor configurations, photooxidation kinetics/mechanisms and comparison with other Advanced Oxidation Processes (e.g., UV/H2O2, ozonation, UV/O3, Fenton and photo-Fenton reactions), visible light-induced dye decomposition by sensitization mechanism, reaction intermediates and toxicity issues, and real-world process scenarios. © 2008 Elsevier B.V. All rights reserved.