Diffusion with simultaneous reaction of reactive dyes in cellulose. II. Effect of hydrolysis

<jats:title>Abstract</jats:title><jats:p>Theoretical equations that describe the concentration profiles of immobilized and active species for reactive dyes were derived from the diffusion equation accompanied by the reaction with cellulose and water in the substrate. The diffusion coefficient <jats:italic>D</jats:italic> and the rate constant of the reaction with cellulose, <jats:italic>k</jats:italic><jats:sub>cell</jats:sub>, and that with water in cellulose, <jats:italic>k</jats:italic><jats:sub><jats:italic>w</jats:italic></jats:sub>, were estimated by using the theoretical equations and the cylindrical film roll method. The theory predicted that the apparent diffusion coefficients decreased with the hydrolysis of active species in cellulose. Results from diffusion experiments with C.I. Reactive Yellow 4 and Orange 1 show that the ratio <jats:italic>P</jats:italic> of <jats:italic>k</jats:italic><jats:sub><jats:italic>w</jats:italic></jats:sub> to <jats:italic>k</jats:italic><jats:sub>cell</jats:sub> for Orange 1 increased with increase in pH to about pH 13 and that the <jats:italic>P</jats:italic> for Yellow 4 was smaller than unity. Using an alternative experiment to diffusion, <jats:italic>P</jats:italic> of Orange 1 was measured to be 1.0–1.5, and that of Yellow 4 was smaller than unity at pH 11.6 at 30°C. It was therefore concluded that the <jats:italic>D</jats:italic> of active species was constant to a highly alkaline region and that the decrease in the apparent diffusion coefficient of Orange 1 was mainly due to the hydrolysis of active species in cellulose.</jats:p>