Characterisation of exhausted reactive dyebath and its reuse after nanofiltration and ozonation

Abstract

Reactive dyeing of cotton requires 100 150 L of water and 0 3 to 14 kg of salt per kg of the fabric depending on the type of machines dyes and depth of shade The exhausted dyebath and first rinse accounting for about 20 of the waste volume and containing high levels of the dye and salt is the major polluting stream The present study is an attempt to provide an integrated approach for the decolorisation and reuse of the exhausted reactive dyebath by nanofiltration and ozonation Detailed characterization of the dye bath and first rinse was done by collecting samples from cotton knitwear textile dyeing units employing High Exhaust reactive dyes in Winch and Soft flow dyeing machines and Low Salt reactive dyes in Soft flow machines and analyzing in terms of their pH Electrical Conductivity Total Suspended Solids Total Dissolved Solids Color major ions Chemical Oxygen Demand and Total Organic Carbon The studies revealed that the dyebath and first rinse contained 80 of the salt load It is highly alkaline intensely colored and has high TDS and COD newline