Adsorption behavior of reactive dyes on cellulose

The adsorption of three anionic dyes (CI Reactive Red 120, a monochlorotriazinyl red dye (Red E), and CI Direct Blue I) on cellulose was investigated from a neutral dyebath at 80 degrees C over a wide concentration range of sodium sulfate. Because of the apparent low substantivity, no accurate adsorption was determined at low electrolyte concentrations, where a higher apparent substantivity of the dyes was observed. The standard chemical potential differences between the cellulose and solution phases, or the standard affinity, -Delta mu(0), for these dyes were calculated on the basis of the Donnan equilibrium model. CI Reactive Red 120 and CI Direct Blue I showed saturation in the adsorption isotherm, while Red E had a likeness to the other dyes when a high salt concentration was used. The substantivity of several reactive dye ranges is discussed, comparing them with the present results. (C) 1997 Elsevier Science Ltd.