This document discusses key production variables that affect ceramic membranes, including raw materials, fabrication methods, sintering temperature, and coating techniques. Raw materials like kaolin clay and fly ash can lower costs, while additives like zeolites and apatite suit different applications. Fabrication by slip casting, extrusion or pressing yields different strengths. Higher sintering temperatures increase properties but must be below melting points. Coating methods like sol-gel, CVD and ALD can precisely control layer thickness but require specialized equipment. Process variables must be optimized to produce high-performance ceramic membranes.

1. CERAMIC MEMBRANES - ASSESSMENT OF
PRODUCTION VARIABLES
Eng. Kareem Hossam Ahmed Mokhtar
Teaching Assistant in Egyptian Academy for Engineering
and Advanced Technology

2. LAYOUT
INTRODUCTION
MEMBRANE TECHNOLOGIES
TYPES OF CERAMIC MEMBRANES
FABRICATION OF CERAMIC MEMBRANES
 OVERVIEW
 RAW MATERIAL
 ADDITIVES
 SHAPING
 SINTERING
 COATING

3. INTRODUCTION
97%,
3%
Earth Water
Salt Water (Oceans) Fresh water

4. Water Crisis
Population
explosion
Water
Pollution
Inefficient
irrigation
Regional
upheavals

5. MEMBRANE TECHNOLOGY
• MEMBRANE SEPARATION TECHNOLOGY HAS BECOME INCREASINGLY
APPEALING TO ADDRESS VARIOUS SCIENTIFIC AND TECHNOLOGICAL
ISSUES ASSOCIATED TO POLLUTIONS TREATMENT.
• MEMBRANE IS A LAYER THAT ALLOW ELEMENTS
TO PASS SELECTIVELY
• MEMBRANES CAN BE CLASSIFIED INTO DIFFERENT
CATEGORIES.

6. CLASSIFICATION OF MEMBRANES – DRIVING
FORCE
Driving Force Examples
Pressure driven  Reverse osmosis.
 Microfiltration
 Ultrafiltration
 Nano-filtration
Concentration gradient  Dialysis
Temperature driven  Membrane distillation
Electrical potential  Electrodialysis

7. CLASSIFICATION OF CERAMIC MEMBRANES –
MATERIAL
Polymeric membranes Ceramic membranes
Advantages Low cost Low fouling
High temperature
stability
Resistance to chlorine
Disadvantages High fouling
Low temperature
stability
Lower life time
compared to ceramic
membranes
High cost

8. POINTS OF STRENGTH OF CERAMIC
MEMBRANES
Thermal stability
Chemical stability
High mechanical strength
Ceramic
Membrane
Interstice
properties

9. CERAMIC MEMBRANES
• CERAMIC MEMBRANES CONSIST MAINLY OF SUPPORTIVE LAYER,
INTERMEDIATE LAYER, AND SELECTIVE LAYER.

10. FABRICATION PROCESS

11. PRODUCTION VARIABLES IN CERAMIC
MEMBRANES
• RAW MATERIALS
• FABRICATION METHOD
• SINTERING TEMPERATURE
• COATING

12. RAW MATERIALS

13. DIFFERENT RAW MATERIALS USED IN
CERAMIC MEMBRANES
0
5
10
15
20
25
30
clays Kaolin Fly ash Quartz sand Apatite Natural Zeolite Portland
cement
Rice Husk ash Sugarcane
bagasse ash
Geopolymer
%
usage

14. THE EFFECT OF RAW MATERIALS AND
ADDITIVES
1- COST
• LOW-COST RAW MATERIALS MUST BE SELECTED SUCH AS KAOLIN CLAY IN
ADDITION TO THE USAGE OF FLY ASH AND RICE HUSK. IN THIS WAY THE RAW
MATERIAL COST WILL BE REDUCED THUS REDUCING THE FINAL PRODUCTION
COST OF THE MEMBRANE

15. THE EFFECT OF RAW MATERIALS AND
ADDITIVES
COST
The Material Used for the Preparation of Membrane
Cost of Raw Material
(USD) to produce 1 m2
Fly ash and titania 2
Fly ash quartz and calcium carbonate 5
Kaolin, ball clay, feldspar, calcium carbonate, and pyrophyllite 10
Fly ash, calcium carbonate, sodium carbonate, and boric acid 17
Clay, sodium metasilicate, sodium carbonate, and boric acid 19
Fly ash, quartz, calcium carbonate, and titania 25
Kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, sodium
metasilicate, and polyvinyl alcohol 78
kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium
metasilicate 130

16. THE EFFECT OF RAW MATERIALS AND
ADDITIVES
2- FINAL APPLICATION
• ZEOLITES ARE KNOWN FOR THEIR SUPERIOR AMMONIA ION ABSORPTIVITY, WHICH
IS ADVANTAGEOUS FOR APPLICATIONS IN THE TREATMENT OF FERTILIZER
CONTAMINATED WATER.
• APATITE IS NOT ONLY ABLE TO EFFICIENTLY ADSORB METAL CONTAMINANTS BUT
ARE ALSO EFFECTIVE IN THE REMOVAL OF ANIONIC AND CATIONIC DYES BY
ADSORPTION.

17. THE EFFECT OF RAW MATERIALS AND
ADDITIVES
3- PORE FORMING AGENT
• THEY ARE USED TO INCREASE THE POROSITY AND PERMEABILITY OF THE
MEMBRANES.
• THE QUANTITY OF PORE FORMING AGENT IS DIRECTLY PROPORTIONAL TO
POROSITY, HOWEVER IT IS INVERSELY PROPORTION TO THE STRENGTH OF
THE MEMBRANE.
• USING PORE FORMING AGENT EXCESSIVELY ALSO CAUSES INCREASE IN THE
SHRINKAGE OF MEMBRANE.

18. FABRICATION METHOD
• SLIP CASTING
• EXTRUSION
• PRESSING

19. PREPARATION METHOD - SLIP CASTING
• THE SLURRY IS POURED IN A MICROPOROUS MOLD, DUE TO CAPILLARY
SUCTION, THE MOISTURE IS DRAWN
• AFTER GETTING THE DESIRED THICKNESS, THE EXCESS IS POURED AND THE
MOLD IS LEFT TO DRY.
• HEATING AND SINTERING TAKE PLACE TO
PRODUCE THE FINAL PRODUCT

20. PREPARATION METHOD - SLIP CASTING
• IT CAN BE USED TO PRODUCE COMPLEX SHAPES
• THE RATIO BETWEEN THE WATER AND THE POWDER MUST BE ACCURATE TO
FORM THE SLURRY
• IT REQUIRES LONG TIME
• THE THICKNESS OF THE WALL IS HARD TO BE CONTROLLED

21. PREPARATION METHOD - EXTRUSION
• THE MIXTURE IS MIXED TO FORM A HOMOGENOUS MIXTURE
• PUSHED THROUGH NOZZLES IN AN EXTRUDER
• THE PRODUCT IS TUBULAR IN SHAPE THAT HAS A HIGH STRENGTH
• THE PREPARATION NEEDS TO BE PRECISE

22. PREPARATION METHOD - PRESSING
• UNIAXIAL PRESSING IS USED
• DRY MIXTURE IS NEEDED (<2 WT% WATER)
• DUE TO PRESSING A RIGID STRUCTURE IS OBTAINED
• THE PRODUCT HAS HIGH MECHANICAL STRENGTH SO IT CAN BE USED IN HIGH
PRESSURE APPLICATIONS

23. THERMAL TREATMENT

24. THERMAL TREATMENT

25. SINTERING TEMPERATURE
• IT IS ONE OF THE MOST IMPORTANT STEPS IN THE MANUFACTURING OF THE
MEMBRANE; AS IN THIS STEP THE MEMBRANE GETS ITS STRENGTH AND
STRUCTURE.
• THE TEMPERATURE OF SINTERING PROCESS IS CHOSEN BELOW THE MELTING
POINT OF THE RAW MATERIAL.
• CHOOSING THE SINTERING TEMPERATURE IS CRUCIAL AS IT AFFECTS THE
PORE SIZE, PERMEABILITY, CRYSTAL SIZE, MECHANICAL STRENGTH AND
CHEMICAL RESISTANCE.

26. SINTERING TEMPERATURE
Effect of increasing
sintering temperature
Justification
Pore size Increases Due to forming large pores and elimination
of small pores
Permeability Increases Due to formation of larger pore sizes
Mechanical strength Increases Due to formation of low crystal size which
leads to densified membranes
Chemical resistance Increases Based on laboratory studies.

27. COATING
• DIP COATING
• SOL-GEL
• CHEMICAL VAPOR DEPOSITION (CVD)
• ATOMIC LAYER DEPOSITION (ALD)

28. COATING (DIP-COATING)
• DIP-COATING CAN BE USED FOR THE COATINGS OF SOLS OR SUSPENSIONS
OF POWDERS
• A DRY SUBSTRATE IS DIPPED INTO A CERAMIC POWDER SUSPENSION OR SOL
AND THEN WITHDRAWN FROM IT
• ENABLING THE MEMBRANE SURFACE
TO ABSORB A LAYER OF SUSPENSION
OR SOL DUE TO THE CAPILLARY FORCES.
• ONCE THE LAYER COMES INTO
CONTACT WITH THE ATMOSPHERE IT
WILL RAPIDLY DRY THEN CALCINATION
TAKES PLACE.

29. COATING (DIP-COATING)
• FLEXIBILITY AND EASE OF OPERATION
• FREQUENTLY USED FOR CERAMIC MEMBRANE MODIFICATION

30. COATING (SOL-GEL)
• APPROPRIATE FOR MAKING THIN AND POROUS LAYERS WITH
CONTROLLABLE POROSITY
• PROVIDES MEMBRANES WITH RELATIVELY THIN TOP LAYERS
• THE PRECURSOR SOL CAN EITHER BE DEPOSITED ON
THE MEMBRANE SUPPORT TO FORM A TOP LAYER
OR CAST INTO A SUITABLE CONTAINER WITH THE
DESIRED SHAPE

31. COATING (SOL-GEL)
• SOL-GEL METHOD AIMS FOR NARROWING MEMBRANE PORE SIZES AND
ENDOWING A LOWER FOULING SURFACE.
• THE PREPARATION SHOULD BE DONE IN A DUST-FREE ENVIRONMENT.
• PARTIAL GELATION IN THE SOL SHOULD BE AVOIDED.

32. COATING (CVD)
• THE PORE STRUCTURE AND PORE SIZE ARE OPTIMIZED TO IMPROVE THE
SELECTIVITY OF CERAMIC MEMBRANES
• THE REACTION OF ONE OR SEVERAL GAS PHASE PRECURSORS INSIDE OR
AROUND THE SUBSTRATE PORES
• A THIN FILM IS DEPOSITED ON THE POROUS SUBSTRATE AT A TEMPERATURE
BETWEEN 400 AND 1000 ◦C

33. COATING (ALD)
• DEPOSITING UNIFORM FILMS ON COMPLEX SUPPORTS
• TWO OR MORE PRECURSORS ARE MADE TO REACT WITH ONE ANOTHER
CYCLICALLY.
• ONE REACTION CYCLE INVOLVES FOUR DIFFERENT STEPS:
• EXPOSURE OF THE FIRST REACTANT A
• PURGING OF THE REACTION CHAMBER TO REMOVE
UNREACTED PRECURSORS AND BY-PRODUCTS
• EXPOSURE OF THE SECOND REACTANT B
• FURTHER PURGING.

34. COATING (ALD)
• ALD IS DONE AT A MUCH LOWER TEMPERATURE THAN CVD
• ALD CAN PRECISELY CONTROL THE THICKNESS OF THE FILM AT THE
ANGSTROM OR MONOLAYER LEVEL WITH A HIGH QUALITY

35. COATING- GENERAL COMPARISON
• ALL THESE MODIFICATION METHODS HAVE BEEN FOUND TO BE EFFECTIVE TO
IMPROVE CERAMIC MEMBRANE PERFORMANCE
• SOL-GEL COATING GIVES A THINNER LAYER (50 NM–4 µm) THAN THE DIP-
COATING METHOD
• SOL-GEL AND DIP-COATING ARE MATURE TECHNIQUES FOR THE FABRICATION
OF COMMERCIAL CERAMIC MEMBRANES

36. COATING- COMPARISON
• CVD AND ALD CAN OBTAIN A RELATIVELY THIN FILM ON SUBSTRATES.
ESPECIALLY, THE ALD CAN ACHIEVE A THIN LAYER WITH ATOMIC LAYER
THICKNESS, WITH THE POTENTIAL TO CONTROL MEMBRANE PORE SIZES AT
THE NANOSCALE.
• CVD AND ALD HAS WIDELY BEEN USED FOR THE DEPOSITION OF INORGANIC
AND ORGANIC THIN FILMS. THAT IS WHY THEY ARE SUPPOSED TO BE MORE
EFFECTIVE
• CVD HAS BEEN SCALED UP FOR CERAMIC MEMBRANE PREPARATIONS MAINLY
FOR GAS SEPARATION
• ALD IS CONSIDERED AS ONE OF THE MOST PROMISING METHODS TO FINE
TUNE MEMBRANE SURFACE PROPERTIES AND PORE STRUCTURES