MICROFILTRATION - UB

MICROFILTRATION

NUR ISTIANAH,ST.MT.,M.Eng

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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 molecules

semi-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


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


Range of membrane capabilities for food application


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


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


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


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)



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


20

Flate

Spiral

Hollow


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


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.


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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MICROFILTRATION - UB

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