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

Abstract

The key to achieving sustainable development lies in reducing waste, valorizing waste, and adopting conscious consumption. This study aimed to evaluate the potential of two by-products from the cork industry as natural dyes for textiles. Specifically, cork-cooking wastewater and expanded black cork condensate were tested as eco-friendly coloring agents to dye cotton (both organic and with a surface treatment) and wool. After dyeing, the colored fabric samples were subjected to washing with hot and cold water, as well as natural light exposure, to assess color fastness. The color assessment at the end was performed using ΔE*, which is a parameter that quantifies the magnitude of a color difference, comparing the L*a*b* color coordinates from the CIELAB system of the dyed samples with those of the control sample. The magnitude of ΔE* (>5) showed that, in all cases, the fabric samples exhibited a different color from the controls. However, the best coloring performance was achieved with expanded black cork condensate in wool samples, resulting in a uniform dark brown color (ΔE* = 42.48 ± 0.19). Additionally, the cationized cotton samples showed an interesting brownish-grey hue (ΔE * = 35.02 ± 0.42), indicating that the surface treatment promoted dye fixation, since the organic cotton achieved only a light brown color (ΔE * = 14.52 ± 0.39) and was less resistant to light exposure. Natural dyeing using cork extract presents a sustainable, eco-friendly, and non-toxic alternative for textile dyeing. Furthermore, the observed bacteriostatic effect indicates the potential for producing functionalized colored textiles with great interest in medical applications. The process results in unique and earthy tones while promoting the sustainable use of natural resources and preserving the environment.

Phenolic Compounds from By-Products for Functional Textiles

“…In the few instances where by-products were liquid in nature, direct dyeing with the by-product could be achieved [77,100]. However, in most cases, phenolic compounds from solid by-products needed to be extracted to be applied to textile fabrics.…”

Grape Pomace (Vitis vinifera L.) Waste Valorization: Assessing Its Potential as a Sustainable Natural Dye for Textiles Applications

“…The waste from the food industry and invasive plants have been the subject of research as potential sources of biodyes for the textile industry, constituting excellent examples of case studies in the context of waste valorization. In recent years, successful coloring of cotton and wool fabrics has been achieved, resulting in a diverse range of earthy colors, utilizing waste materials from strawberry tree (Arbutus unedo L.) fruits [11], wine production [12], as well as by-products from the cork industry, including cork-cooking wastewater and expanded black cork condensate [13]. The use of plant waste as a coloring agent has also gained importance in recent years.…”