Reusing wastewater of madder natural dye for wool dyeing

Natural dye is environment-friendly which is usually extracted from vegetative material. In this work, the wastewater of madder dyebath is reused for wool dyeing. Initially, the madder absorption behavior on wool fiber is determined by new methods based on spectroscopic information of dye solution. The absorbance spectra change is explained in terms of absorbability of chemical components of madder on wool by using several techniques such as principal component analysis, colorimetry, statistical and derivative spectroscopy techniques. The obtained results indicate that the chemical components of the initial dye solution are different from those remaining in the exhausted dye solution. In reusing wastewater of wool dyeing with madder, the exhausted dyebath is reconstructed by adding madder and water. The analyzing color parameter and fastness properties of samples indicate that the quality of samples dyed in reconstructed dyebath is the same as initial wool dyeing. The economic analysis shows that the reusing wastewater caused 19.91% cost saving in wool dyeing with madder.