NOVEL COMBINATION OF TRISODIUM CITRATE AND TRISODIUM PHOSPHATE IN REACTIVE DYEING OF COTTON: AN ATTEMPT TO REDUCE ENVIRONMENTAL IMPACT

"Reactive dyes are most widely used for dyeing cellulosic fabrics due to their excellent wet fastness properties, the brilliancy of shades and a wide gamut of colours. However, the exhaustion of reactive dye requires a large quantity of inorganic electrolyte, which results in excessive total dissolved solids (TDS) values of the resultant effluent. Such high TDS-containing effluents are challenging to treat and require advanced treatment techniques. The discharge of high-TDS containing effluent into water-bodies can increase the salinity of the aquatic system, which can affect the delicate biochemistry of the aquatic life. This necessitates the exploration of alternative chemicals for reducing the TDS of the effluents in reactive dyeing. The current study explores the alternate combination of trisodium citrate (TSC) and trisodium phosphate (TSP) as an eco-friendly replacement of inorganic salts and alkali in the dyeing of cotton by the exhaust process. The TSC-TSP combination resulted in an insignificant variation in exhaustion, fixation and fastness ratings compared to the conventional salt-soda combination. The colour values showed marginal variations in the individual cases of dyes. However, the use of the TSC-TSP combination showed a great promise in reducing the TDS of the effluent (by 66%), which is a major concern in effluent treatment. TSC being organic, some increase in COD/BOD values was obtained; however, the effluent remained in a category of easily treatable ones. "

The study of direct dye sorption on flax fibers during dyeing

This article presents the study of direct dye sorption onto the flax fiber during the dyeing process in the presence of an inorganic electrolyte. The previously prepared linen fabric was subjected to dyeing by a standard process, varying in concentration and time of dyeing. The results are satisfactory considering that they reveal the character of the direct dye sorption for fibers as well as the capacity and energy adsorption, on the basis of which the process of dyeing can be optimized. The increase of dye concentration in the solution during dyeing decreases, and longer time of dyeing increases the degree of exhaustion. The adsorbed amount of adsorbate on the adsorbent rises during the increase of initial concentration and dyeing time. Langmuir, Freundlich, Temkin and Flory-Huggins models can be used to describe adsorption of a direct dye onto the linen fiber, having in mind the advantage of Flory-Huggins model because of its characteristics in the description of the sorption and maximum values of the coefficient of determination as well.