Membrane and Desalination Technologies - TCE Moodle Website

682 K. Mohanty and R. Ghosh
4.3. Gas-Sparging in Flat-sheet Membrane Modules
Gas sparging in flat-sheet membrane modules has been less extensively studied. The first
experimental work related to gas sparging in a flat-sheet membrane module was reported by
Lee et al. (42). They studied the ultrafiltration of a bacterial suspension using 300 kDa PS
ultrafiltration membrane and reported a 100% increase in permeate flux.
Li et al. (51) examined flux enhancement by gas sparging in flat-sheet membrane modules
using four different protein solutions (HSA, BSA, human immunoglobulin G and lysozyme)
as test media. Two different membranes viz., polysulphone and polyether sulphone having
100 kDa MWCO in each case were used. The effects of gas sparging on permeate flux, single
protein transmission and protein fractionation were extensively studied. Gas sparging
increased the permeate flux by 7–50% and as with other types of membrane modules, was
found to be more effective at lower liquid feed flow rates. Protein transmissions in single
protein ultrafiltration were reduced by gas sparging. Protein transmission was found to be
lower with PS membranes than with PES membranes, this being attributed to protein fouling
(see Table 16.4). However, protein fractionation was enhanced in binary protein ultrafiltration.
Gas sparging affected the transmission of different proteins to different extents and
hence increased selectivity.
Ghosh et al. (52) examined the effect of gas sparging on fractionation of proteins BSA and
lysozyme using a flat-sheet PS membrane having 100 kDa MWCO. Though the enhancement
of permeate flux was reported to be only 10%, gas sparging enhanced the selectivity of
protein fractionation very significantly. Nearly complete separation of BSA and lysozyme
with gas-sparged ultrafiltration was reported. This was attributed to the disruption of concentration
polarization layer and enhanced mass transfer due to bubble-induced secondary flow.
Mercier-Bonin et al. (53) conducted experiments on yeast-cell ultrafiltration using a
ceramic flat-sheet membrane. They also studied the effect of membrane orientation and
found that horizontally installed membrane modules were more efficient in terms of flux
enhancement than vertically installed membrane modules. The maximum flux enhancement
Table 16.4
Effect of gas sparging on protein fractionation
Protein (g/L) Membrane Flux (kg/m 2 h) Transmission (%) Selectivity
NG a
G b
HSA, 4.5 þ IgG, 1.0 PES 100 25.8 31.3 18.5 (HSA) 5.6 3.7 c
9.5 c
68.3 (IgG) 53.1
HSA, 4.5 þ IgG, 1.0 PS 100 22.5 24.7 5.5 (HSA) 1.7 4.25 c
8.9 c
23.4 (IgG) 15.2
BSA, 2.0 þ Lys, 2.0 PES 100 45.5 53.3 38.46 (BSA) 6.04 2.47 14.83
95.27 (Lys) 89.57
a Without gas sparging
b With gas sparging
c Reversed selectivity, the ratio of IgG and HSA transmission
NG a
G b
NG a
G b