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Optimization of Salt-Free Reactive Dyeing Process for Cotton with
Coconut Oil/Water Dual-Phase Dyeing System

In this study, the coconut oil/water dual-phase dyeing system for developing salt-free reactive dyeing
process for cotton was established. The selected dyes in this work were hot-dyeing reactive dyes,
including C.I. Reactive Red 243, C.I. Reactive Blue 214 and C.I. Reactive Orange 70. A dual-phase
dyeing system was performed under various coconut oil to water ratios and a comparative study was
conducted on the conventional aqueous-based reactive dyeing in the presence and absence of salt. The
results showed that the oil to water ratio of 3:1 imparted the highest colour yields (K/S values) and
achieved a superior colour yield to the conventional aqueous-based dyeing. The results also pointed
out that better dye fixation could be attained by dyeing cotton with the coconut oil/water dual-phase
dyeing process under the optimum conditions. A comparable degree of dye exhaustion was observed
for the aqueous-based and the dual-phase dyeing processes, however, the dye fixation was higher for
the dual-phase dyeing, indicating less dye hydrolysis in this dyeing system. Consequently, superior
colour fastnesses to washing and rubbing were obtained, less dye staining was observed in the case of
dual-phase dyeing. A study on reusability of the coconut oil recovered from the spent dyebath for
another reactive dyeing cycle was also conducted. The oil from the spent dyebath was directly taken to
use without any further purification as a dual-phase medium along with water and the obtained result
indicated a reusability potential of coconut oil. From this research, it infers that cleaner reactive dyeing
process with the coconut oil/water dual-phase system for cotton could be developed.