A membrane is a selective barrier that separates two phases and restricts the transport of molecules, driven by gradients such as pressure and concentration. Various types of membranes and processes, including microfiltration, ultrafiltration, and reverse osmosis, serve different separation needs, with advantages like continuous operation but challenges like fouling and membrane cost. Applications range from concentration and purification to fractionation of mixtures.

2. WHAT IS A MEMBRANE?
It is defined
essentially as a
“Barrier which
separates 2 phases
& restricts
transport of
various molecules
in a selective
manner”.
Driven by
•Pressure
•Concentration
•Temperature
•Electrical potential
Gradients
It can be
• Thick/Thin
• Liquid/Solid
• Symmetric/Asymmetric
• Natural/Synthetic
• Neutral/Charged
• Homogeneous/Heterog-
eneous

3. MATERIALS USED:
Synthetic polymeric membranes:
Ceramic membranes
Teflon
PolyVinyliDineFluoride
PolyPropylene
PolyEthylene
Cellulose esters
PolyCarbonate
PSf/PES
PolyImide/PolyEtherImide
PolyEtherEtherKetoneAlumina, Al2O3
Silicium Carbide, SiC

4. MEMBRANE MODULES:
• PLATE-AND-FRAME MODULE
• SPIRAL-WOUND MODULE
• HOLLOW-FIBER
MODULE

5. WORKING MECHANISM:
• MEMBRANE PROCESS: THE FEED STREAM IS DIVIDED INTO TWO
STREAMS:
• RETENTATE (CONCENTRATE) STREAM
• PERMEATE STREAM
• EITHER THE CONCENTRATE OR PERMEATE STREAM IS THE
PRODUCT OF OUR INTEREST.

6. TYPESOFLOW:
Feed
Permeate
Permeate
Feed Retentate
1. Dead-end 2. Cross-flow

7. IDEALMEMBRANE
Permeate Feed
Driving ForceREALMEMBRANE
Phase 1Phase 2
SCH. REPRESENTATION OF MEMBRANE SEPARATION:

8. WHAT IS A MEMBRANE?
I

10. MEMBRANE PROCESSES:
• FIRST GENERATION MEMBRANE PROCESSES
• MICROFILTRATION (MF)
• ULTRAFILTRATION (UF)
• NANOFILTRATION (NF)
• HYPER FILTRATION (HF) /REVERSE OSMOSIS (RO)
• ELECTRO DIALYSIS (ED)
• SECOND GENERATION MEMBRANE PROCESSES
• MEMBRANE DISTILLATION (MD)

11. MICROFILTRATION (MF):
• SEPARATES SUSPENDED SOLIDS AND SOME COLLOIDAL MATERIALS (>0.1Μ)
FROM A FEED STREAM.
• THE CONCENTRATE REQUIRES PERIODIC REMOVAL OR CLEANING TO
PREVENT THE EVENTUAL PLUGGING OF MEMBRANE FEED PASSAGE WAYS.
• PORE SIZE : 0.1- 5 MICROMETRE
• PRESSURE : 1-10 BAR

12. ULTRAFILTRATION (UF):
• SEPARATES COLLOIDAL MATERIAL, EMULSIFIED OILS, MICRO
BIOLOGICAL MATERIALS, AND LARGE ORGANIC MOLECULES.
• SOMEWHAT DEPENDENT ON CHARGE OF THE PARTICLE, AND
IS MUCH MORE CONCERNED WITH THE SIZE OF THE PARTICLE.
• PORE SIZES RANGES: 1-100 NM
• PRESSURE :1-10 BAR
• TYPICALLY NOT EFFECTIVE AT SEPARATING ORGANIC
STREAMS

13. NANOFILTRATION (NF):
• USED WHEN LOW MOLECULAR WEIGHT SOLUTES SUCH AS
INORGANIC SALTS/ SMALL ORGANIC MOLECULES (GLUCOSE,
SUCROSE) HAVE TO BE SEPARATED.
• USES A MEMBRANE THAT IS PARTIALLY PERMEABLE TO PERFORM
THE SEPARATION (LIKE IN RO), BUT NF PORES >> RO PORES
• CAN OPERATE AT MUCH LOWER PRESSURES, AND PASSES SOME OF
THE INORGANIC SALTS DUE TO LARGER PORE SIZE
• PORE SIZE :- 0.5-10 NM
• PRESSURE : 10-30 BAR

14. REVERSE OSMOSIS (RO) (HYPER FILTRATION):
• SPECIFICALLY USED FOR THE SEPARATION OF DISSOLVED IONS FROM
WATER (DISSOLVED SOLIDS, BACTERIA, VIRUSES, SALTS, PROTEINS, AND
OTHER GERMS)
• ESSENTIALLY A PRESSURE DRIVEN MEMBRANE DIFFUSION PROCESS FOR
SEPARATING DISSOLVED SOLUTES.
• RELATIVELY A LOW ENERGY PROCESS.
• SMALLEST PORE STRUCTURE (<0.5 NM)
• ALLOWS ONLY THE SMALLEST ORGANIC MOLECULES AND
UNCHANGED SOLUTES TO PASS THROUGH THE SEMI-PERMEABLE
MEMBRANE ALONG WITH THE WATER
• >95-99% OF INORGANIC SALTS AND CHARGED ORGANICS WILL ALSO
BE REJECTED BY THE MEMBRANE DUE TO CHARGE REPULSION
ESTABLISHED AT THE MEMBRANE SURFACE
• PRESSURE:- 35-100 BAR

16. METHODS TO REDUCE FOULING:
a. Heat treatment
b. pH adjustament
c. Chlorination
d. Adsorption onto active carbon
a. Hydraulic cleaning
b. Mechanical cleaning
c. Chemical cleaning

17. ADVANTAGES:
• NO SPECIFIC CHEMICAL KNOWLEDGE IS NEEDED FOR
OPERATION
• NO COMPLEX INSTRUMENTATION
• BASIC CONCEPT IS SIMPLE TO UNDERSTAND
• SEPARATION CAN BE CARRIED OUT CONTINUOUSLY
• MEMBRANE PROCESSES CAN EASILY BE COMBINED WITH OTHER
SEPARATION PROCESSES
• SEPARATION CAN BE CARRIED OUT UNDER MILD CONDITIONS
• MEMBRANE PROPERTIES ARE VARIABLE AND CAN BE ADJUSTED
• GREATER DESIGN FLEXIBILITY IN DESIGNING SYSTEMS
• CLEAN TECHNOLOGY WITH OPERATIONAL EASE

18. DISADVANTAGES:
• MEMBRANES ARE RELATIVELY EXPENSIVE
• CERTAIN SOLVENTS, COLLOIDAL SOLIDS, ESPECIALLY
GRAPHITE AND OTHER RESIDUES CAN QUICKLY AND
PERMANENTLY DESTROY THE MEMBRANE SURFACES
• OIL EMULSIONS ARE NOT "CHEMICALLY SEPARATED," SO
SECONDARY OIL RECOVERY CAN BE DIFFICULT.
• SYNTHETICS ARE NOT EFFECTIVELY TREATED BY THIS METHOD
• MEMBRANE FOULING;
• LOW MEMBRANE LIFETIME;

19. APPLICATIONS:
• CONCENTRATION: THE DESIRED COMPONENT
IS PRESENT IN A LOW CONCENTRATION AND
SOLVENT HAS TO BE REMOVED;
• PURIFICATION: UNDESIRABLE IMPURITIES
HAVE TO BE REMOVED;
• FRACTIONATION: A MIXTURE MUST BE
SEPARATED INTO TWO OR MORE DESIRED
COMPONENTS.