Separation Of Dyes From Cotton Dyeing Effluent Using Cationic Polyelectrolytes

The separation of reactive, sulfur, and vat dyes from cotton dyeing effluent was investigated by a coagulation process using a cationic polymer electrolyte (PE). The coagulation of dyes was found to be considerably influenced by the amount of added PE and pH of the effluent. High degree of separation, (i.e.-90-99%) could be achieved for all the dyes. The secondary treatment of the PE treated (primary treatment) with Alum was investigated. This treatment was effective in increasing the dye separation by removing the last traces of the dye from the primary treated effluent. The reuse of recovered dye for subsequent cotton dyeing operations has been explored. Introduction Textile wet processing involves the use of a variety of chemicals comprising various classes of dyes and other chemicals, known as auxiliary chemicals. The waste water stream from the textile dyeing operation, therefore, contains unutilized dyes and auxiliary chemicals along with a large amount of Water. The pollution load on the liquid effluent increases with subsequent steps of chemical processing where the contribution of one single dyeing step amounts to about 8-20% of the total pollution load due to incomplete exhaustion of the dye.' The water consumption in chemical Processing operation varies from 50300 L for every kg of the processing goods. A mill processing 100,000 MT of cotton per day may require water varying from 2.5 to 4.0 million liters per day. About 40,000 to 80,000 tons of dyes are American Dyestuff Reporter 0 February 19 rable I: Four dye types studied.