Effect of dyebath alkali in salt-free reactive dyeing of cotton to reduce effluent load

The conventional reactive dyeing method of cotton fabric uses a large amount of Glauber salt for exhaustion. The large quantity of salt is an indirect threat to the environment and aquatic life as it produces toxic effluents and increases the salinity of discharged water, and also creates osmotic imbalance by increasing total dissolved solids. Elevated salinity also has significant adverse effects on plant growth and agricultural production. The present work focuses on salt-free dyeing of cotton fabric with reactive Remazol Red 198 (RR198) dye in the presence of alkali. The proposed method was evaluated by the color strength and fastness properties of the dyed fabrics. Various fastness properties (color fastness to wash, water, perspiration, rubbing and light) presented satisfactory results, mostly in the range of 4-5 (on a scale of 5). The maximum color strength value (K/S) obtained was 4.8, which is significant for optimum depth of shade. The CIE Delta E value was 0.29 for 1% shade, which is within the permitted limit. Moreover, there was no evidence of any deterioration in the fabric's strength. Wastewater produced in the salt-free dyeing approaches had better water quality than wastewater produced using the conventional dyeing method. Therefore, from an eco-friendly dyeing perspective, the suggested dyeing procedure is attractive.