Direct electrochemical reduction of vat dyes in a fixed bed of graphite granules

Roessler, Albert; Crettenand, David

doi:10.1016/j.dyepig.2004.01.005

Cited by 69 publications

(14 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[11] With the advent of the modern chemical industry and after the introduction of chemical methods, at the end of the 19th century, specifically with the accessibility of the reducing agent sodium dithionite (Na 2 S 2 O 4 ), the dyeing process also become achievable on the industrial scale. Although there are several modern methods for reducing indigo to leuco indigo, including electrochemical [12] and bacterial methods, the more conventional is still the use of Na 2 S 2 O 4 in alkaline media. [13,14] Despite the importance of this form of indigo, the literature is scarce, particularly with regards to the spectral and photophysical properties of leuco indigo.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Excited States of Indigo Derivatives in their Reduced Forms

2010

View full text Add to dashboard Cite

A comprehensive characterization of the electronic spectral and photophysical properties of the leuco (reduced) form of several indigo derivatives, including indigo and Tyrian Purple, with di-, tetra-, and hexa-substitution, was obtained in solution. The characterization involves absorption, fluorescence, and triplet-triplet absorption spectra, together with quantitative measurements of quantum yields of fluorescence, phi(F) (0.46-0.04), intersystem crossing, phi(Tau) (0.013-0.034), internal conversion, phi(IC), and the corresponding lifetimes. The position and degree of substitution promote differences in the spectral and photophysical properties displayed by the investigated leuco derivatives. The phi(F) values are about two orders of magnitude higher than those previously obtained for the corresponding keto forms. Also in contrast with the behavior found for the keto forms, the S(1) approximately approximately -->T(1) intersystem crossing is an efficient route for the excited-state deactivation channel. These findings strengthen the fact that, in contrast to keto indigo where the internal conversion dominates the deactivation of the excited-state, with leuco indigo (and derivatives), the excited state deactivation involves competition between internal conversion, triplet state formation, and fluorescence. A time-resolved investigation of one of the compounds in glycerol showed the presence of a photoisomerization process.

show abstract

Section: Introductionmentioning

confidence: 99%

Characterization of the Excited States of Indigo Derivatives in their Reduced Forms

2010

View full text Add to dashboard Cite

show abstract

“…These efforts offered considerable environmental improvements by removing the need for the harmful chemicals used in indigo synthesis; however, a reducing agent was still required to reduce the insoluble indigo to the soluble leucoindigo for dyeing. A number of other strategies (for example, bacterial fermentation 12,13 , catalytic hydrogenation 14 , and electrochemical reduction 15 ) have been used to reduce indigo, but none are as fast-acting and cost-effective as sodium dithionite.…”

mentioning

confidence: 99%

Employing a biochemical protecting group for a sustainable indigo dyeing strategy

et al. 2018

View full text Add to dashboard Cite

Indigo is an ancient dye uniquely capable of producing the signature tones in blue denim; however, the dyeing process requires chemical steps that are environmentally damaging. We describe a sustainable dyeing strategy that not only circumvents the use of toxic reagents for indigo chemical synthesis but also removes the need for a reducing agent for dye solubilization. This strategy utilizes a glucose moiety as a biochemical protecting group to stabilize the reactive indigo precursor indoxyl to form indican, preventing spontaneous oxidation to crystalline indigo during microbial fermentation. Application of a β-glucosidase removes the protecting group from indican, resulting in indigo crystal formation in the cotton fibers. We identified the gene coding for the glucosyltransferase PtUGT1 from the indigo plant Polygonum tinctorium and solved the structure of PtUGT1. Heterologous expression of PtUGT1 in Escherichia coli supported high indican conversion, and biosynthesized indican was used to dye cotton swatches and a garment.

show abstract

“…Five dyeing parameters were studied: the concentration of FeSO 4 , NaOH, alkaline protease, indigo and temperature. Th ese factors, with their coded values according to the 3 5 Box-Behnken experimental design, are presented in Table 2. Using these fi ve parameters (factors), each with three levels, a 3 5 Box-Behnken design was run to obtain a set of data (run), consisting of a total of 46 runs with six replicates at the central point.…”

Section: Statistical Analysis Of Dyed Cottonmentioning

confidence: 99%

“…Th e problems associated with the use of Na 2 S 2 O 4 have led to the search for alternative, non-dithionitebased reduction systems. Th ese include the application of iron (II) salts, together with gluconic acid and NaOH at 60 °C [3][4][5], and iron (II) salts in combination with tartaric or citric acid, triethanolamine and NaOH at room temperature [6][7]. All these reduction systems showed results comparable to sodium dithionite with some exceptions.…”

Section: Introductionmentioning

confidence: 99%

Dyeing of Cotton with Indigo Using Alkaline Protease and Additives

Mazumdar¹,

Chakraborty²

2019

TEK

View full text Add to dashboard Cite

Indigo is invariably applied on cotton to produce an attractive blue shade, together with the desired wash-down eff ects. Because it is water insoluble, indigo is reduced and solubilised with sodium dithionite and NaOH to develop affi nity for cotton. Sodium dithionite dissociates into hazardous by-products viz. sulphate, sulphite and thiosulphate with a harmful eff ect on the environment due to their toxicity, as well as a corrosive eff ect on waste lines. To overcome these problems, the eco-friendliness of alkaline protease, together with iron (II) sulphate (FeSO 4) as a reducing agent, was studied as a replacement for sodium dithionite. Dyed samples were characterised by attenuated total refl ection, using Fourier transformation infrared spectroscopy, scanning electron microscope and X-ray diff raction (XRD). It was observed that alkaline protease, together with iron (II) sulphate, is also capable of producing a comparable reduction potential in dye baths, reduction bath stability, and the surface colour strength and colour fastness properties of dyed cotton compared to those obtained using sodium dithionite.

show abstract

Direct electrochemical reduction of vat dyes in a fixed bed of graphite granules

Cited by 69 publications

References 13 publications

Characterization of the Excited States of Indigo Derivatives in their Reduced Forms

Characterization of the Excited States of Indigo Derivatives in their Reduced Forms

Employing a biochemical protecting group for a sustainable indigo dyeing strategy

Dyeing of Cotton with Indigo Using Alkaline Protease and Additives

Contact Info

Product

Resources

About