Abstract Eco-friendly textile dyeing technologies are increasingly popular because of raised environmental consciousness and the need for less polluting substitutes wefor synthetic dyes. Waste of black tea is an appropriate source of polyphenols and tannins with ecological as well as functional benefits, such as microbial resistance, and antioxidant activity. Herein, a new method for eco-friendlier dyeing and finishing of viscose fabric using black tea waste extract (BTWE) as a sustainable natural colorant for dyeing and functional finishing of viscose fabric was examined. The dyeing conditions, like pH, temperature, dye concentration, and time, were systematically regulated to assign the proper conditions for maximum color strength (K/S). The colorfastness of the dyed fabric against washing, perspiration, crocking, and light was determined. Using zinc oxide nanoparticles (ZnO-NPs) improved the performance of the dyed fabrics by making them more resistant to some pathogens. The results revealed that the optimum dyeing conditions were found to be pH 3, 45 °C, 4% dye, for 60 min. Finishing the dyed samples with ZnO-NPs enhanced the K/S and antimicrobial activity without negative impact on the mechanical strength. The dyed viscose fabric exhibited excellent resistance towards Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria as well as the fungus Candida albicans . The antioxidant activity of the dyed samples was greatly improved compared to undyed viscose fabric. However, enhancement of the ultraviolet protection factor of the dyed fabric was limited, likely due to inadequate surface coverage and lack of coating operations. The discrepancy in the chemical and morphological structures between the undyed and the corresponding dyed viscose fabrics was monitored using Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The correlation between the different dyeing parameters and the color strength as well as the colorimetric data was assigned using analysis of variance (ANOVA). The findings of this investigation justify the potential application of BTWE as a green colorant for one-pot sustainable dyeing and functional finishing of viscose fabrics.
Rasmy et al. (2026) studied this question.