Electrochemical reduction processes in indigo dyeing

Abstract

The application of indirect electrolysis as a reduction technique in indigo dyeing is described. Various reversible redox systems were tested to determine whether they are suitable for indigo dyeing. The results of the dyeing trials confirm that the process engineering involved can be applied to the production of denim. The new process offers environmental benefits and offers the prospects of improved process stability, because the reduction state in the dyebath can be readily monitored by measuring reduction potential.

Electrochemical and sonoelectrochemical monitoring of indigo reduction by glucose

“…The indirect electrochemical reduction uses mediators such as redox active iron complexes and anthraquinones to transfer electrons between electrode and dye molecule [8,9]. However, there are inherent limitations to the electrochemical approach.…”

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

“…Sodium dithionite has been for long the main industrial reducing agent but its consumption in the vat contributes to environmentally harmful wastes from the dyeworks. There is interest in alternative chemical and electrochemical means of reduction [9][10][11][12]. Glucose has been investigated previously for sulphur dye reduction [13] and it is considered to be a possible alternative reducing agent for indigo [14].…”

Iron-complexes of bis(2-hydroxyethyl)-amino-compounds as mediators for the indirect reduction of dispersed vat dyes – Cyclic voltammetry and spectroelectrochemical experiments

“…Successful indirect dyestuff reduction leads to catalytic currents and as a result an increase of cathodic peak current (I p ) c is observed according to the following equations [11][12][13][14] Fe III L + eFe II L (1) cat. reaction 2 Fe II L + Dye Dye 2-+ 2 Fe III L (2) where Dye = CI Vat Yellow 1 and CI Vat Blue 5, L = TEA, MET, DISPO. For homogeneous chemical systems, theoretical solutions to calculate relevant kinetic information from cyclic voltammograms are available in the literature [11,12,14].…”

“…Direct and indirect cathodic dyestuff reduction have been studied intensively within the last decade because of their particular relevance for dyestuff production and textile dye application in case of vat dyes, sulfur dyes and indigo [1][2][3][4][5][6][7]. From an introduction of electrochemical methods for dyestuff reduction several advantages are expected:…”