MICROFILTRATION
NUR ISTIANAH,ST.MT.,M.Eng
is a VERY THIN film that allows some types of matter to pass through while leaving others behind
Membrane
= materials which have voids in them letting some molecules pass more conveniently than some other moleculessemi- permeable membrane
Retentate
Permeate Membrane
Feed
CONCEPT
Nur Istianah-T.Membrani-2016
Driving force :
3. Voltage difference, 1. Pressure difference
2. Concentration difference
4. Temperature difference,
RO
UF
MF
Pervaporation
Dialysis
Membrane extraction
Electrodialysis
Membrane distillation
Nur Istianah-T.Membrani-2016
0.0001 0.001 0.01 0.1 1 10 100mm
hair Crypto-
sporidium smallest
micro- organism polio
virus
Suspended solids
Parasites Bacteria Org. macro. molecules
Viruses Colloids Dissolved salts
Sand filtration Microfiltration
Ultrafiltration Nanofiltration
Reverse Osmosis
ZW500: 0.04 um ZW1000: 0.02 um
TYPES OF PROCESSES
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Range of membrane capabilities for food application
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MICROFILTRATION
• largest pores
• a sterile filtration with pores 0.1-10.0 microns
• micro-organisms cannot pass through them
• operated at low pressure differences
• used to filter particles(Retain particles by a purely sieving mechanism)
• may or may not be assymmetric
• lower pressures than RO
Nur Istianah-T.Membrani-2016
MICROFILTRATION
• Microfiltration separates micron-sized particles from fluids.
• The membrane modules used for microfiltration are similar in design to those used for
ultrafiltration.
• A microfiltration process can be operated either
in normal flow mode or cross-flow mode
MICROFILTRATION
• In microfiltration, the accumulated particles are
• brought back to the feed solution primarily by shear induced erosion of the cake.
• Back flushing is a common method by which
cakes formed by particles can be removed
from membranes.
– pharmaceutical industry – food & beverages
– chemical industry
– microelectronics industry – laboratory/analytical uses – biotechnology
MICROFILTRATION
Nur Istianah-T.Membrani-2016
1. Cell harvesting from bioreactors 2. Virus removal for pharmaceutical products
3. Clarification of fruit juice and beverages 4. Water purification
5. Air filtration
6. Sterilization of products 7. Concentration of biomass
MICROFILTRATION
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Material of membrane
Hydrophilic polymers
Hydrophobic polymers
preferentially permit water permeation
(e.g. poly (vinyl alcohol) or cellulose acetate)
preferentially permit permeation of organic materials.
e.g. Poly (dimethylsiloxane) or poly (trimethylsilylpropyne)
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The important factors in determining the performance of a membrane
Thickness
Molecular structure
Chemical
composition
Flat membranes
Spiral wound membranes
Hollow-fiber membranes
Very-small-diameter hollow fibers, the high-pressure feed enters the shell side at one end and leaves at the other end (closed)
Membrane Configurations
Three basic structures are commonly uses for membranes:
homogeneous, asymmetric, and composite
Constructed from flat sheet membranes separated by spacer screens, and susceptible to fouling by particulates
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20
Flate
Spiral
Hollow
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Advantages :
Continuous separation
Low energy requirement
Meet various separation demands
reduce the loss of volatiles or changes to nutritional or eating quality of food
simple installation with lower labour and operating costs
Nur Istianah-T.Membrani-2016
Disdvantages :
higher capital costs than evaporation
maximum concentration to 30% total solids
fouling of the membranes (deposition of
polymers), which reduces the operating time between membrane cleaning.
Nur Istianah-T.Membrani-2016
Rate of microfiltration
Example
Bacterial cells having 0.8 micron average diameter are being microfiltered in the cross-flow mode using a membrane having an area of 100 cm2. The steady state cake layer formed on the membrane has a thickness of 10 microns and a porosity of 0.35. If the viscosity of the filtrate obtained is 1.4 centipoise, predict the volumetric permeate flux at a transmembrane pressure of 50 kPa.
When pure water (viscosity = 1 centipoise) was filtered
through the same membrane at the same
transmembrane pressure, the permeate flux obtained
was 10"4 m/s.
Solution
For pure water microfiltration this equation can be written as shown below:
The specific cake resistance of the bacterial cell cake can be calculated
using equation (11.23):
Solution
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