Olive mill wastewater: A potential source of natural dyes for textile dyeing

Olive mill wastewater (OMW) is a by-product of the olive oil extraction process. Around 30 million m3 of OMW are produced annually in the Mediterranean area, causing environmental concern. In spite of being a serious ecological problem, OMW can represent a possible resource for the dyeing of textile materials. It contains a valuable source of abundant natural colouring substances.The present study reports the valorization of OMW by its use as a possible dyebath for dyeing wool. It was found that protein fibers possess high affinity to the aqueous extract of OMW giving darker shades with generally good fastnesses. The effect of dyebath pH, dyebath temperature, dyeing time and salt addition on the dyeability of wool were investigated. The effect of mordant type with different mordanting methods on dyeing quality was also studied. The results showed that mordanting gave deeper shades and enhanced fastness properties.

► The olive mill wastewater (OMW) causes a serious ecological problem.
► OMW contains a valuable source of abundant natural colouring substances.
► OMW was used to dye woollen fibers at different dyeing conditions.
► The obtained shades were darker with generally good fastnesses.
► Mordanting improved generally light fastness.