Algae extracts have emerged as a sustainable and eco-friendly alternative to synthetic dyes and functional additives in the textile industry, particularly for dyeing and functionalizing of cotton fabrics. Herein, two types of water-soluble algae extracts from Arthrospira platensis and Porphyridium cruentum were characterized in terms of thermal, structural, and functional properties and used as dye and/or functional agents. Cotton samples were pre-treated with chitosan and alum mordants and compared with commercially treated cationic cotton. The algae extracts were applied through the exhaust method, with variations in temperature, pH, liquor ratio, temperature rise gradient, and extract percentages. The resulting colours, assessed through CIE L*a*b* coordinates and K/S values using UV–Vis spectroscopy, displayed green and pink coloration, with commercial cationic cotton exhibiting more intense colours. Colour fastness measurements were also performed on functionalized cotton fabrics. The water-based algae extracts and functionalized samples were additionally characterized for functional features, displaying an antioxidant activity exceeding 60% (68.13 ± 3.60 and 60.76 ± 1.18, for A. platensis and P. cruentum, respectively). This work highlights their dual role in providing both aesthetic dyeing and functional enhancement of cotton. By using renewable marine resources and eco-friendly water-based processes, this approach supports the development of greener, more sustainable textile technologies.
Oliveira et al. (2026) studied this question.