Experimental determination of intraparticle diffusivity and fluid film mass transfer coefficient using batch contactors

The mass transfer properties of adsorbates are generally critical factors for design of a fixed bed adsorber. For single-component systems, the completely mixed batch reactor (CMBR) method is a convenient and frequently used experimental technique for determining mass transfer properties. However, the effect of fluid film mass transfer resistance is neglected in the conventional analytical technique of CMBR method when estimating the intraparticle diffusivity (DS). This effect should be considered to determine the diffusivities more accurately. In this study, a new analytical technique was proposed for determination of DS and fluid film mass transfer coefficient (kF) from one concentration decay curve and it was applied in practical experiments. This technique will be useful to estimate diffusivities when the fluid film mass transfer resistance cannot be regarded as being negligible. Under the experimental conditions of this study, the fluid film mass transfer resistance could be neglected at high stirring speeds (i.e., >200 rpm). Therefore, values of DS can be estimated by the conventional technique from kinetic experiments performed at relatively high stirring speeds. On the other hand, values of kF obtained by the proposed technique showed a similar tendency to values estimated from Hixson's empirical equation.