Biomedical Engineering Reference
In-Depth Information
1. Measure the rejection coefficient, R, for the project and contaminants.
2. Calculate adsorptive losses from a mass balance on the product.
Y
ads
¼ðC
R0
V
R0
C
Rf
V
Rf
C
Pf
V
Pf
Þ=A
adsorptive loss (mg/m
2
); C
R0
, C
Rf
, C
Pf
¼
where Y
ads
¼
initial and final retentate/
permeate concentration; V
R0
, V
Rf
, V
Pf
¼
initial and final retentate/permeate
membrane area.
3. Calculate the % product loss (or % contaminant removal) at a given diafiltration
volume.
volume; A
¼
h
i
1
e
ðV
p
=V
0
Þð1RÞ
Y ¼
100
1
where Y
¼
% solute recovered in permeate, V
p
¼
final permeate volume, and
V
0
¼
initial feed volume.
6.6 TFF OPERATING PARAMETER DESIGN
To design quality into the TFF operation requires an understanding the dominant mass
transfer principles governing permeate flux. There are four major operating parameters
that can be controlled on a TFF system:
1. Transmembrane pressure
2. Cross-flow velocity that when normalized to the membrane area is termed the
cross-flow flux (CFF)
3. Feed concentration
4. Temperature
Transmembrane pressure is the primary driving force for convective transport
through the membrane pores and results in solvent flow from the feed to the permeate
stream as shown in Fig. 6.5. The transmembrane pressure can be calculated from the
following equation.
¼
ðP
feed
P
permeate
ÞþðP
retentate
P
permeate
Þ
2
TMP
feed
þ
TMP
retentate
2
TMP
¼
The cross-flow flux is calculated as
¼
Q
R
A
CFF
