Adsorption of Benzene from Water in a Granular Carbon Bed

Illustration 6,4 Adsorption of Benzene from Water in a Granular Carbon Bed 

Adsorption in a fixed bed (a) adsorbent concentration profiles (b) fiuid phase concentration breakthrough curve. 

Here v and Aq are the fluid velocity and cross-sectional area of tiie bed, respectively, and Pf and are the fluid and bed densities. 

The last term in this equation is generally negligible because the bulk of the impurity will reside in the adsorbent. It would otherwise not be a very efficient adsorbent. Equation 6.7a can then be recast in the form 

Equation 6.7a can be used to calculate the time t it takes the front to reach a particular position or, conversely, the position attained after a prescribed time interval. These quantities are, by necessity, limiting lower values because full saturation will in fact be retarded by the mass transfer resistance. However, in many instances the fluid flow is sufficiently slow that local equilibrium is attained, or will be nearly attained, during the interval of contact. We make use of this fact in Illustration 6.6 to analyze the contamination of soil that results from polluted groundwater. 

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