Attempts to reduce water and chemical usage in the removal of bifunctional reactive dyes from cotton: Part 2 bis(vinyl sulfone), aminochlorotriazine/vinyl sulfone and bis(aminochlorotriazine/vinyl sulfone) dyes

Dyeings on cotton obtained using three commercial bifunctional reactive dyes were subjected to a standard, five-stage method which employed a proprietary wash-off agent as well as a three stage, chemical-free wash-off process. Dyeings obtained using both wash-off methods were of the same colour and displayed similar levels of fastness to repeated washing at 60 °C. Lowering the number of wash-off stages from five to three and replacing the wash-off agent with 98 °C water rinses reduced considerably, both the COD and, especially, BOD5 compared with the standard wash-off method, with no increase in COD/BOD5 ratio. The three-bath wash-off method therefore offers potential savings in water usage, compared to the standard method and also eliminates the need for chemicals to be employed in wash-off.