Environmentally friendly dyeing of cotton in an ethanol–water mixture with excellent exhaustion

Abstract

Conventional cotton dyeing methods rely on high salt concentrations and consume large amounts of water. To decrease the ecological impact of the textile industry, the development of a green and sustainable dyeing method for cotton fibres is essential. In the present work, ethanol was used to reduce the amounts of salt and water required for cotton dyeing. Cotton yarns were pretreated with alkali and then dyed with six reactive dyes in a 90 : 10 (v/v) ethanol–water mixture. Using various techniques, including transmission electron microscopy, the effects of ethanol on the particle size and zeta potential of the reactive dyes were examined in detail. Compared with conventionally dyed samples, the cotton yarns dyed in the ethanol–water system using the investigated reactive dyes exhibited enhanced exhaustion, total fixation, and colour strength in the absence of salt. Industrial-scale cotton bobbins produced using the developed method showed commercially acceptable levelness and reproducibility. This method affords a substantial reduction in eutrophication potential and wastewater effluent load, which would considerably improve the environmental cost of cotton dyeing processes. This eco-friendly dyeing process has considerable potential for application to a broad range of natural fibres.