New Laccase-Mediated System Utilized for Bio-Discoloration of Indigo-Dyed Denim Fabrics

In this study, indigo-dyed denim fabric was decolorized by washing and printing with separate and simultaneous applications of laccase enzyme, sodium hydrosulfite, and cellulase enzyme. In this regard, the surface reflectance and color coordinates of the discolored fabrics were analyzed, and SEM photographs of the treated fabrics were prepared to analyze their surfaces. Finally, the effects of the discoloration process and materials on various parameters of the treated samples were investigated, including moisture content, creaserecovery angle, air permeability, and abrasion resistance. The color experiments showed that the discoloration mechanism with the combined use of laccase enzyme, sodium hydrosulfite, and cellulose enzyme had a significant effect on the improvement of the lightness (L*) of the samples, as the lightness of the treated samples was improved by 101.18 percent and 55.79 percent in both printing and washing, respectively. Furthermore, examination of specimen color coordinates revealed that the hue of the treated samples was changed to blue and green, and the purity of color (C*) was improved. The increased moisture content and air permeability of the treated specimens suggested that the comfort of the jeans clothing provided by these treatment methods had improved. As a result, it should be noted that the mediating action of sodium hydrosulfite was significantly influential for discoloration of denim with the laccase enzyme.

Cu(II)/sodium borohydride-based electrocatalytic system for reduction and dyeing of indigo

Purpose To improve the problems as the heavy burden of sewage treatment and environmental pollution caused by the traditional sodium hydrosulfite reduction dyeing of indigo, this study aims to carry out the direct electrochemical reduction dyeing for indigo with the eco-friendly Cu(II)/sodium borohydride reduction system under normal temperature and pressure conditions. Design/methodology/approach The electrochemical behavior of Cu(II)/sodium borohydride reduction system was investigated by cyclic voltammetry. And, the dyeing performance of the Cu(II)/sodium borohydride reduction system was developed by optimizing the concentration of copper sulfate in the anode electrolyte, applied voltage and reduction time via single-factor and orthogonal integrated analysis. Findings The dyeing performance of the Cu(II)/sodium borohydride reduction system is superior to that of the traditional reduction dyeing with sodium hydrosulfite. In the case of the optimized condition, the soaping fastness and dry/wet rubbing fastness of the dyed fabric in the two reduction dyeing processes were basically comparable, the K/S value of electrocatalytic reduction of indigo by Cu(II)/NaBH4 is 11.81, which is higher than that obtained by traditional sodium hydrosulfite reduction dyeing of indigo. Originality/value The innovative electrocatalytic reduction system applied herein uses sodium borohydride as the hydrogen source combined with Cu(II) complex as the catalyst, which can serve as a medium for electron transfer and active the dye molecule to make it easier to be reduced. The electrochemical dyeing strategy presented here provides a new idea to improve the reduction dyeing performance of indigo by sodium borohydride.

Indigo Dyeing of Cotton using Alkaline Catalase and Additives

Sodium hydrosulfite is universally applied as a reducing agent for the reduction of indigo, but also produces hazardous by-products viz. sulfate, sulfite, and thiosulfate ions with harmful effects on the environment due to their toxicity, as well as corrosive effects on the waste lines. To overcome these problems, use of an ecofriendly reducing agent, viz. alkaline catalase, along with iron (II) sulfate, was used in place of sodium hydrosulfite for dyeing of cotton with indigo. Dyed samples were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The alkaline catalase with iron (II) sulfate reducing system produced the same reduction potential in dyebaths, reduction bath stability, surface color strength, and color fastness properties of dyed cotton compared to sodium hydrosulfite use.

Cotton Dyeing with Vat Dyes using Alkaline Pectinase and Iron (II) Salt

Use of sodium hydrosulfite in the dyeing of cotton with vat dyes is criticized for generation of sulfur compounds leading to air and water pollution. In this study, attempts were made to dye cotton with alkaline pectinase along with iron (II) salt as an alternative formulation. A 43 Box-Behnken design was used for statistical analysis of performance for this new reducing system and to obtain optimum parameters for cotton dyeing. The results showed that alkaline pectinase along with iron (II) salt was quite effective in developing comparable dyebath potential, dye receptivity on cotton with comparable dye strength, and colorfastness, as compared to the hydrosulfite-based reducing system. Dyebath stability in presence and absence of dye also showed superior results compared to that of the hydrosulfite system.