The contribution of different vinyl sulphone-reactive dyes to an effluent

Three types of vinyl sulphone dyes were measured in the effluent in this study. The selected dyes were Remazol Yellow RR (mono-functional), Remazol Blue RR (homo bi-functional) and Remazol Red RR (hetero bi-functional). The extinction coefficients of these dyes were measured by creating absorbance versus concentration curves. The absorbance values were obtained by testing standard solutions of each dye in a UV–visible spectrophotometer. The dyeing process was carried out at 4 different dye concentrations (0.025 g/40 ml, 0.05 g/40 ml, 0.10 g/40 ml and 0.15 g/40 ml) on a 5-g fabric sample for each of the dyes. The post-dye liquors and post-wash liquors were tested in an UV–visible spectrophotometer, and their concentrations were calculated using the Beer–Lambert law. The contribution of these dyes to the effluent was calculated and compared, and their adsorption isotherms (Langmuir and Freundlich isotherm) were analysed. The homo bi-functional dye (Blue RR) performed well in the dye bath, but it contributed significantly to the effluent during the washing stages. The mono-functional dye (Yellow RR) was able to adsorb, but it did not perform well due to its greater heterogeneity. The hetero bi-functional Red RR dye was found to be the most environmentally friendly in comparison with the other vinyl sulphone dyes.