what is membrane,material used,membrane module,working mechanism,types of flow,membrane process, methods reducing fouling,advantages

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.