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306 4. Adsorption and Ion Exchange

0.7

0.6

0.5

U(t)
0.4

U(t) , experimental
0.3
U(t) , model

0.2
0 2000 4000 6000 8000 10000 12000
t (sec)
Figure 4.21 The performance of the model.

The liquid-phase diffusion coefficient can be estimated from the Nernst–Haskell eq. (I-24)
(see Appendix I):

RT
D i g
w 2
F
r Fo C u 2 , = 53.6 cm 2 / mol (Table I-8) and thus D 1.4 10 5 cm 2 /s and Sc
i f
alue of v 641.88. For the gi en v k 6.06 10 4 cm/s, the v alue of P is
f s
P N P N D 3 a 5
3
P 0.16 W/m
s
V V
Using the typical dimension ratios of an agitated v essel,

D
B T 1.3 cm
10

Four baffles are selected. Thus, for this specific system, we can assume that N 4 (see
P
alue which is valid for Table 3.4), a v N near or above 2 10 3 . Then, the speed agitation
Re
N 23.35 rpm, which results in a Reynolds number equal to
DN a 2
N 1830
Re

This justifies the use of the selected v alue of N .
p