Investigation of the Thermodynamic and Kinetic Behavior of Acid Dyes in Relation to Wool Fiber Morphology.

Wool fibers from several different sheep breeds in the UK have very limited applications. The main aim of this study was to establish an understanding of the dye sorption properties of different wool fibers through thermodynamics and kinetics of dyeing using Acid Red 1 dye. Wool fibers from Leicester, Ryeland, and Dartmoor sheep breeds were pretreated (to remove impurities) and dyed using Acid Red 1. Leicester showed 7% higher dye exhaustion than Dartmoor wool fibers (20% on mass of fiber). Dyeing equilibrium results for both Leicester and Dartmoor wool fibers were fitted to Langmuir and Freundlich isotherms, and the theoretical maximum sorption capacities were 164 and 144 mg g-1, respectively. Leicester, Ryeland, and Dartmoor also followed the pseudo-second-order reaction kinetics. Thermodynamic parameters like Gibb's free energy (ΔG°) and standard affinity (Δμ°) of the fibers were calculated to understand the interaction of the Acid Red 1 with wool fibers. The difference in dye uptake was explained through the possible involvement of the scale opening gap (surface morphology) of the wool fibers.