WORLD JOURNAL OF ADVANCE
HEALTHCARE RESEARCH

Mahmoud M. Barakat*, Saleh Al. Rahel

ABSTRACT

Indigo is one of the most important vat dyes utilized in the dyeing of cotton fibers; however, its reduction into the water-soluble leuco form traditionally relies on chemical reducing agents, predominantly sodium dithionite, which causes significant environmental problems due to the generation of polluting oxidation by-products. Therefore, this study aimed to evaluate the feasibility of employing indirect electrochemical reduction as an eco-friendly alternative for indigo dyeing, using the iron–triethanolamine (Fe–TEA) complex as an electron-mediator redox catalyst and a stainless steel (SS) cathode. The reduction process was conducted in an alkaline medium, and the resulting leuco-indigo solution was subsequently utilized to dye 100% bleached woven cotton fabrics via the dip–oxidation method. The effects of dye concentration (0.5%, 1%, and 2% weight of fabric [owf]) and sodium hydroxide concentration in the dye bath (11, 13, 15, and 17 g/L) were investigated, in addition to evaluating the recyclability of the dye bath across five consecutive cycles. Dyeing performance was assessed through spectrophotometric reflectance measurements, color strength (K/S) calculations, and CIELAB color coordinates, along with colorfastness evaluations to washing, light, and dry/wet rubbing. The results revealed that increasing the indigo concentration significantly increased color strength (K/S) values and decreased lightness (L*) values, indicating deeper shade yields. However, the dyed samples exhibited poor lightfastness, excellent washfastness, and good overall rubbing fastness, albeit with a slight decrease in wet rubbing fastness. Furthermore, increasing the sodium hydroxide concentration led to an enhancement in color yield while maintaining washfastness and lightfastness properties with a minor reduction in rubbing fastness. Recycling experiments demonstrated the feasibility of reusing the dye bath for five consecutive dyeing cycles without compromising dyeing efficiency. These findings confirm that indirect electrochemical reduction utilizing the Fe–TEA complex on a stainless steel electrode represents a promising, eco-friendly, and cost-effective alternative to conventional chemical reduction methods in indigo dyeing, offering effective dye bath recyclability along with satisfactory colorimetric and fastness properties.

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