Natural dyeing of cellulose fibers using syzygium cumini fruit extracts and a bio-mordant: A step toward sustainable dyeing

Increasing environmental awareness has led to a growing interest in natural dyes in the textile dyeing industry as the consumers become more aware of the toxicity of synthetic dyes that are harmful to the environment and health. Although natural dyes are environmentally friendly compared to synthetic dyes, in general their performance is less than that synthetic dyes. Typically, metallic mordants are used to enhance the affinity of natural dyes to textile materials, perhaps this process breaks the journey of the green story. In this work, we perform the potential alternative for the metal mordant and used soy protein as bio-mordant for dyeing cotton fabric with a natural dye extracted from Syzygium cumini fruits. Sonochemical mordanting and dyeing were examined compared with the conventional water bath. In the experiments, characteristics such as ultrasonic power, temperature, pH, dyeing duration, and dye concentration were examined during the dyeing process. FT-IR, color measurements, washing, crocking, and light fastness tests were used to monitor the effects of the bio-mordant in both conventional and ultrasonic baths. Overall, the sonochemical-assisted dyeing was shown considerably increase the dye absorption and K/S values as compared to the conventional bath. Experiments in this work yield valuable insights into the development of green routes toward the utilization of natural dyes and bio-mordants on natural cellulose-based materials. Using the soy protein mordanted and Syzygium cumini colored fabrics as a comparison, it was found that the sonic dyeing method costs 9.56 €/kg while conventional dyeing methods cost 9.91 €/kg, as the sonicated dyeing method required less cost (i.e., € 0.35) than the conventional bath techniques, nevertheless, sonicated produce darker color than the conventional method. Meanwhile, the cost for dyeing with metal mordant is increased as it severely required a wastewater treatment plant (WWTP). More than that, metal mordant is not a sustainable choice.