THE EXTERNAL MASS TRANSFER OF BASIC AND ACIDIC DYES ON WOOD.

The parameters affecting the initial adsorption rates of Astrazone Blue dye (Basic Blue 69) on to wood have been studied. A simple model is proposed to determine the external mass transfer coefficients and these have been compared with values obtained using a more complex procedure. The external mass transfer coefficient, beta , has been shown to vary linearly with agitation and initial dye concentration using log-log coordinates; furthermore beta is independent of particle size. The effect of temperature has been studied and the activation energy for the process is 44 plus or minus 2 kJ mol** minus **1. Similar correlations were obtained for the adsorption of Telon Blue dye (Acid Blue 25) on wood. Using log-log correlations, the external mass transfer coefficient was found to vary with (rev min** minus **1)**0**. **1**4, C//0** minus **0**. **2**7; and a small dependence on particle size was also observed.