Almond skin, a bio-waste for green dyeing of wool fibres

During the industrial processing of almond fruits, tons of almond skins are generated. Valorization of blanched almond skin wastes by recovering natural polyphenols using water, instead of organic solvents, for direct application of aqueous baths for dyeing of wool fabrics was studied in this work. The results showed that it was possible to recover polyphenols from almond skins and use them as a dye for wool fibres. Kinetics of extraction was modelled by using the diffusion-based Chrastil’s model and Peleg’s empirical model, obtaining excellent fit in both cases (R2 > 0.96). The amount of polyphenol extracted was enough to achieve correct direct dyeing with excellent washing, rubbing and perspiration fastness although the shades obtained were dull. Nevertheless, it was possible to achieve a better coloration by using ion(II) sulfate as the mordant resulting in dyeings with reasonable good washing and rubbing fastness.