Researchers developed a novel method of cotton dyeing with improved dye fixation

Cotton and other cellulose substrates comprise over 40% of the world’s textile consumption. Cotton dyeing with reactive dye requires enormous amounts of salts to facilitate dye adsorption. Large quantities of water are used to clean hydrolyzed dyes, which generates larger volumes of wastewater and consumes high energy. The amount of salts ranges from 5 to 125 on the weight of fabric. As a result, conventional reactive dyeing is not environmentally friendly. Researchers are trying hard to reduce pollution to the environment by the dyeing of cotton.

Recently a report published by the prestigious research journal, Cellulose, highlighted a silicone reverse emulsion dyeing system to dye cellulosic textile with reactive dye. When the dye amount is the same, the color depth of the dyed cotton fiber is 13.82, and the fixation of dye is 87.76% in the new process. In the traditional water-based dyeing system, the color depth of dyed cotton fiber and dye fixation is only 9.31, 56.63%, respectively. Therefore, the new method improved the dye fixation by 31.13% and reduced the effluent discharge by 72%.

The silicone reverse emulsion dyeing system contains a small amount of water. These dyeing conditions may reduce the hydrolysis of dye. The energy gap between vinyl sulfone and b-hydroxyethyl sulfone is 51.0 kcal/mol in the aqueous system, which is lower than in the silicone reverse emulsion dyeing system (52.2 kcal/mol in silicone).

The same trend is observed for the energy gap between the triazine dye and the hydroxyl triazine dye (26.5 kcal/mol in silicone vs. 22.8 kcal/mol in water), confirming that the hydrolysis of the bifunctional reactive ye needs higher energy in the silicone reverse emulsion dyeing system.

The utilization of the new method could be a sustainable approach to reduce dye wastage and environmental pollution.

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