Assessment of Reactive Dyeing of Cotton using Seawater

Abstract

This study investigated the effects of auxiliary chemicals on reactive dyeing of cotton fabric using seawater as an alternative to freshwater. The study involved dyeing of 100% cotton fabric with reactive blue 21 using both fresh and seawater. The effects of Na₂SO₄, NaCl and Na₂CO₃ auxiliaries were assessed on dye exhaustion, fixation and colour strength. Reactive dyeing using seawater with a pH 9 which contained Na⁺ (882.4 mg/L), Cl^- (938 mg/L), Ca²⁺ (1200 mg/L), CO₃^-2(3000 mg/L), Mg²⁺(1030 mg/L) and alkalinity (4615 mg/L), resulted in exhaustion rate of 54%, colour strength of 0.098 and fixation rate of 44%. While dyeing using freshwater gave exhaustion rate of 34%, colour strength of 0.026 and fixation rate of 34%. When auxiliaries were added, the exhaustion, colour strength and fixation for freshwater dyeing were 66%, 0.199 and 84%, respectively. In contrast for seawater dyeing, the corresponding results were 56% for exhaustion, 0.53 for colour strength, and 76% for fixation. These results showed that seawater’s natural electrolytes reduced the need for additional chemicals but also led to excessive auxiliary concentrations that hindered dye performance. Freshwater dyeing, by contrast, showed higher dye exhaustion, colour strength, and fixation when auxiliaries were added. Given the rising demand for freshwater and the high-water consumption in textile dyeing, particularly with reactive dyes, the seawater could be a viable substitute. Therefore, seawater is a feasible alternative for textile dyeing, provided chemical adjustments are made to optimize dye exhaustion and fixation.