Valorization of Cork Industry By-Products as Sustainable Natural Dyes for Textiles

The key to achievingsustainable development lies in reducing waste,valorizing waste, and adopting conscious consumption. This study aimedto evaluate the potential of two by-products from the cork industryas natural dyes for textiles. Specifically, cork-cooking wastewaterand expanded black cork condensate were tested as eco-friendly coloringagents to dye cotton (both organic and with a surface treatment) andwool. After dyeing, the colored fabric samples were subjected to washingwith hot and cold water, as well as natural light exposure, to assesscolor fastness. The color assessment at the end was performed using & UDelta;E*, which is a parameter that quantifies themagnitude of a color difference, comparing the L*a*b* color coordinates from the CIELABsystem of the dyed samples with those of the control sample. The magnitudeof & UDelta;E* (>5) showed that, in all cases, thefabric samples exhibited a different color from the controls. However,the best coloring performance was achieved with expanded black corkcondensate in wool samples, resulting in a uniform dark brown color(& UDelta;E* = 42.48 & PLUSMN; 0.19). Additionally, thecationized cotton samples showed an interesting brownish-grey hue(& UDelta;E * = 35.02 & PLUSMN; 0.42), indicating thatthe surface treatment promoted dye fixation, since the organic cottonachieved only a light brown color (& UDelta;E * = 14.52 & PLUSMN; 0.39) and was less resistant to light exposure. Natural dyeingusing cork extract presents a sustainable, eco-friendly, and non-toxicalternative for textile dyeing. Furthermore, the observed bacteriostaticeffect indicates the potential for producing functionalized coloredtextiles with great interest in medical applications. The processresults in unique and earthy tones while promoting the sustainableuse of natural resources and preserving the environment. Natural dyes from cork industry by-productspromote sustainable,healthy processes in textiles, enhancing circularity in the industry.