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Introduction of innovate membranes in water-treatment
Young June Won
Water Environment-Membrane Technology Lab.School of Chemical and Biological Engineering, Seoul National University, Korea
2013. 11. 12
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Source:UNEP/ GWI*IPCC : Intergovernment Panel on Climate Change
Plentiful Supply Relatively sufficientInsufficient water
Water stressWater scarcity
IPCC(유엔 국제 기후변화 위원회)* 는 지구온난화와 엘니뇨 현상으로 21세기말 지구의기온은 6.4도, 해수면은 59Cm 상승되어 물 부족 사태가 가속화될 것으로 전망함.
세계 수자원 시장 전망
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WATER TREATMENT BUSINESS
Schematic Diagram for Water Treatment
수처리는 사용 목적에 맞도록 물의 품질을 개선시키는 모든 처리를 말하며,
고도처리를 통한 Water Reuse는 해수 담수화와 더불어 가장 빠르게 확보할 수 있는대체 수자원 공급 방법임
고도처리의 종류에는 Membrane, UV, Ozone, GAC 등이 있음
* WWT: Waste-Water Treatment
Qua
lity
of W
ater
Source
Usage
Wastewater
Water Reuse
Effluent
Time Sequence
• Agricultural : 74%• Municipal : 14%• Industrial : 12%
• Surface / Ground water : 3%• Seawater : 97%
(Global market 2005~2015,IDA report)
: Core business segment
• Advanced WWT• Reuse Treatment
• Conventional WWT*
• Desalination• Water Treatment
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Hydrology Molecular biology Surface Chem Nano particles
Biofilm CFD Catalyst
Grey water
Drinking water
Ecological water
Recreation
Industrial water
Ground water recharge
Space station Shower water
Fusion Tech
Application of Membrane Processes in Water Environment
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분리막의 종류 – 공극 크기에 따른 구분
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분리막의 종류 – 외형에 따른 구분
Flat sheet
Hollow fiber
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분리막을 이용한 수처리 공정 구성
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분리막을 이용한 공정의 대표적인 문제점
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Conventional preparation method
Part 1
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Conventional membrane preparation
Process Materials
Phase inversion by• Solvent evaporation• Temperature change• Precipitant addition
Polymers:Cellulose acetate, polyamidePolypropylene, polyamidePolysulfone, nitrocellulose
Stretching sheets of partiallycrystalline polymers
Polymers:PTFE
Irradiation and etching Polymers:Polycarbonate, polyester
Molding and sintering of fine-grainpowders
Polymers:PTFE, polyethylene
Source: Adapted from Ripperger and Schulz, 1986
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Material MF UF RO
Cellulose esters (mixed)Cellulose nitratePolyamide, aliphatic (e.g., Nylon)Polycarbonate (track-etch)Polyester (track-etch)PolypropylenePolytetrafluoroethylene (PTFE)Cellulose (regenerated)Polyacrylonitrile (PAN)Polyvinyl alcohol (PVA)Polysulfone (PSF)Polyethersulfone (PES)Cellulose acetate (CA)Cellulose triacetate (CTA)Polyamide, aromatic (PA)Polyimide (PI)CA/CTA BlendsComposites (e.g., polyacrylic acid on zirconia or stainless steel)Composites, polymeric thin film (e.g., PA or polyetherurea on PSF)Polybenzimidazole (PBI)Polyetherimide (PEI)
OOOOOOOOOOOOOOO
OOOOOOOOO
OOOOOOOOO
Polymer used in membrane preparation
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Sintering
heat
SilicalitePowder of glass
CarbonPowdre of graphite
Aluminium oxideZirconium oxide
Powder of ceramics
Stinless steel, tungsten
Powder of metals
PolyethylenePTFEPolypropylene
Powders of Polymers
SilicalitePowder of glass
CarbonPowdre of graphite
Aluminium oxideZirconium oxide
Powder of ceramics
Stinless steel, tungsten
Powder of metals
PolyethylenePTFEPolypropylene
Powders of Polymers
Schematic of the process Materials used
Membrane pore size distribution 0.1 – 10 mPorosity: 10-20% with polymers80% with metals
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Application of sintered membranes:
Filtration of colloidal solution and suspensions
Gas separation
Separation of radioactive isotopes
Sintering
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• Films of polyethylene or polytetrafluoroethylene are extruded at temperatures close to the Tm (melting point).
• After annealing and cooling, the film is stretched perpendicular to the direction of drawing.
• Membranes with high permeability to gas and vapor but impermeable to aqueous solution can be obtained from hydrophobic polymers as PTFE.
These membranes are ideal for application as
Membrane Contactors
PTFE membrane obtained by stretching
Stretching
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It is a two step process:A film is first subjected to high energy particle radiation and, then,
immersed in a etching bath
Track-etching
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Symmetric membranes having uniform and cylindrical pores can be obtained.
• The pore density is determined by the residence time in the irradiator.• The pore diameter is controlled by the residence time in the etching bath.
Track-etching
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• This technique is the most versatile preparation method.
• Membranes with different morphology (porous or dense), structures (asymmetric or symmetric) and function can be prepared.
• A homogeneous system, consisting of the polymer dissolved in an appropriate solvent, in a single phase (liquid), is transformed, through a process of separation/solidification, in a two phase system:
• A polymer rich phase, solid, which will form themembrane itself;
• A polymer lean phase, liquid, which will form themembrane pores.
Phase inversion method
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The only thermodynamic presumption for all procedures is that the system must have a miscibility gap over a defined concentration/temperature range
There are several techniques of preparation of membranes by phase inversion, which are listed below:
EIPS = Evaporation induced phase separationVIPS = Vapor induced phase separationTIPS = Temperature induced phase separationNIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation
The type of Phase inversion method
What is the miscibility gap ?
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Phase diagram in binary polymer system
Polymer
Solvent Non-Solvent
binodal
spinodal
Miscibility gap
A
B
Critical point
A casting solution
B membrane porosity
B’ polymer-lean phase
B’’ polymer-rich phase
Liquid phase
B’
B’’
Metastabile region:
No precipitation, but nucleation and growth
Unstable region:
Phase separation
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The only thermodynamic presumption for all procedures is that the system must have a miscibility gap over a defined concentration/temperature range
There are several techniques of preparation of membranes by phase inversion, which are listed below:
EIPS = Evaporation induced phase separationVIPS = Vapor induced phase separationTIPS = Temperature induced phase separationNIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation
Phase separation caused by evaporation
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The only thermodynamic presumption for all procedures is that the system must have a miscibility gap over a defined concentration/temperature range
There are several techniques of preparation of membranes by phase inversion, which are listed below:
EIPS = Evaporation induced phase separationVIPS = Vapor induced phase separationTIPS = Temperature induced phase separationNIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation
Phase separation caused by vapor
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The only thermodynamic presumption for all procedures is that the system must have a miscibility gap over a defined concentration/temperature range
There are several techniques of preparation of membranes by phase inversion, which are listed below:
EIPS = Evaporation induced phase separationVIPS = Vapor induced phase separationTIPS = Temperature induced phase separationNIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation
Thermal induced phase separation
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Metastabile region:
No precipitation, but nucleation and growth
T
T2
A
B’ B B’’
Solid phase
binodal
spinodal
T1
Solvent Polymer
Critical point
Liquid phase
A casting solution
B membrane porosity
B’ polymer-lean phase
B’’ polymer-rich phase
Unstable region:
Phase separation
Mechanism of TIPs
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The only thermodynamic presumption for all procedures is that the system must have a miscibility gap over a defined concentration/temperature range
There are several techniques of preparation of membranes by phase inversion, which are listed below:
EIPS = Evaporation induced phase separationVIPS = Vapor induced phase separationTIPS = Temperature induced phase separationNIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation
Phase Inversion Method
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Polymer
Solvent Nonsolvent
Binodal
Spinodal
Solidification
Unstable
MetastableStable
Polymer rich phasePolymer lean phase
Polymer lean phase
Polymer rich phase
Bead-like
Bicontinuous
Cellular
Tie line
Phase diagram in binary polymer system
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Polymer
Solvent Non-solvent
Binodal
Spinodal
Unstable
Liquid-liquid de-mixing
Polymeric solution was demixed into polymer, solvent, and nonsolvent
Non-solvent (Water)Inward diffusion
Solvent (DMF)Outward diffusionDiffusion
Solution(PVDF+DMF)
PDMS
SP
N
Mechanisms – L-L demixing
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Structure of membrane prepared by PI
1) Sponge like structure 2) Finger like structure
Why ?
Symmetric structure Asymmetric structure
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Substrate (PET film)
Substrate (PET film)
Homogeneous PVDF solution
Coagulation bath
Pure water only
Substrate (PET film)
Water + solvent bath
Finger like structure
Sponge
water
DMF
PVDF
Mechanisms – membrane structure
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Skin Formation :
polymer solution gelation medium
P + SNS[P]
R >> 1
R > 1
R >> 1
R > 1
Defect-Free Skin
Porous Skin
Mechanisms – membrane structure
Finger like structure
Sponge like structure
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1) Preparation of the polymeric dope
PolymerSolvent
Additives
Preparation steps- flat sheet membrane
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Casting knifePolymeric solution
Support
2) Casting
3) Coagulation
4) membrane
Dense skin
Porous support
Preparation steps – flat sheet membrane
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1) Preparation of the polymeric dope
PolymerSolvent
Additives
Preparation steps-hollow fiber
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N2
Pressurized reservoir
Polymeric dope inletBore fluid inlet
Spinneret
Rotating coagulation
bath
Thermocouples
Temperature controlling element
Peristaltic pump
Nascent fibre
2) Hollow fibers spinning
• Wet spinning
• Dry/wet spinning
Polymeric dope
Bore fluid
Preparation steps-hollow fiber
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PMMA plate
Rubber roller
PMMA frame
Glass plate
Silicone gasket
34
Interfacial polymerization
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Polysulfone support
35
Interfacial polymerization – step 1
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Trimesoyl chloride in hexane
36
Interfacial polymerization – step 2
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m-phenylene diamine aqueous solution
37
Interfacial polymerization – step 3
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Polyamide Active Layer
Polysulfone Support Layer
Polyester Backing Layer
0.2 micron
50 micron
150 micron
Interfacial polymerization – step 4
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Membrane material Membrane process
cellulose acetate EP, MF, UF, RO
cellulose esters (mixed) MF, D
polyacrylonitrile (PAN) UF
polyamide (aromatic, aliphatic)
MF, UF, RO, MC
polyimide UF, RO, GS
polypropylene MF, MD, MC
polyethersulfone UF, MF, GS, D
polysulfone UF, MF, GS,D
sulfonated polysulfone UF, RO, NF
polyvinylidenefluoride UF
Electrophoresis (EP), Microfiltration (MF), Ultrafiltration (UF), Reverse Osmosis (RO), Gas separation (GS), Nanofiltration (NF), Dialysis (D), Membrane Distillation (MD), Membrane contactor (MC).
The phase inversion process can make both symmetric and asymmetric membranes with rather different structures from a variety of polymers
Commercial membranes prepared by conventional methods
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NEW membranes to improvethe performance !
Part 2
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• In processes such as reverse osmosis, gas separationand pervaporation, the actual mass separation isachieved by a solution/diffusion mechanism.
• An asymmetric membrane structure is mandatory forthese processes.
Many polymers with satisfactory selectivity and permeability are not well suited for the phase inversion
Composite membranes
1) Composite membrane
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Composite membranes are prepared in a two step process• Manufacturing of the porous support• Deposition of the barrier layer on the surface of this porous support layer
a) Schematic diagram of a composite membrane showing the porous supportstructure and the selective skin layer, and b) scanning electron micrograph of acomposite membrane with polydimethylsiloxane as the selective layer on apolysulfone support structure.
selective layer
porous support
a) b)
1) Composite membrane
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The techniques used for the preparation of composite membranes may be grouped into four general procedures:
• Casting of the barrier layer, e.g. on the surface of a water bath and then laminating it on the porous support film.
• Coating of the porous support film by a polymer, a reactive monomer or pre polymer solution followed by drying or curing with heat or radiation.
• Gas phase deposition of the barrier layer on the porous support film from a glow discharge plasma.
• Interfacial polymerization of reactive monomers on the surface of the porous support film.
Today, the most important technique for preparing composite membranes is interfacial polymerization
1) Composite membrane
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44
1) Schematic diagram of composite membrane
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Example:High-Definition Polymeric Membranes – Construction of 3D LithographedChannel Arrays through Control of Natural Building Blocks Dynamics.
• The fabrication of well-defined interfaces is in high demand in many fields ofbiotechnologies.
• High-definition membrane-like arrays have been developed through the self-assembly of water droplets, which work as natural building blocks for theconstruction of ordered channels.
2) Membranes prepared by block copolymer
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In this work, 3D well-ordered honeycombstructures patterned from PEEK-WC-NO2have been obtained.
In the figure:
top view collected by AFM; layer collected in the bulk of the film by
confocal microscopy; SEM micrograph elucidating the cross
section.
V. Speranza, F. Trotta, E. Drioli and A. Gugliuzza, Applied material and Interfaces, 2010, Vol. 2 N°2, pp. 459-466.
2) Membranes prepared by block copolymer
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3) Introducing the pattern on the membrane surface
The patterns on the membrane surface could disturb the deposition of microbials and enhance the effective area !
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3) Introducing the pattern on the membrane surface
PDMS replica mold
Coagulation bath
Non-woven Fabric(Substrate)
PVDF solution
PVDF membrane
Coagulation bath
Modified immersion precipitation methodConventional immersion
precipitation method
PVDF solution
PVDF membrane
Nascent membrane
Non-woven Fabric(Substrate)
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Top view
10μm
3) Pyramid patterned membrane
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Top view
20μm
3) Prism patterned membrane
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Top view
20μm
3) Embossing patterned membrane
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Flat membrane Prism Patterned membrane
Green : CellRed : Membrane
1213 um1213 um 1213 um
1213 um
3) Introducing the pattern on the membrane surface
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3) Introducing the pattern on the membrane surface
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Si substrate PS colloidal monolayerO2 plasma by
reactive ion etching(Reduced diameter of
colloidal particle)
Ag evaporationPS colloid lift-offHF/H2O2 etching
Si μ-pillar
4) MINs membrane
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MINs membrane with support layer
Pore
Dissolve replica moldwith toluene
UV curing for 2 hrs
UV lamp
Casting knife
Detach PDMS moldfrom replica mold
Master mold
Remove excess MINs with top site of pattern
Replica mold(Poly(styrene-co-maleic
anhydride))
Replica mold
MINs solution
55
PDMS mold
Dissolved replica mold function as adhesive between skin layer and support layer
Flat PDMS mold(w/o pattern)
4) MINs membrane
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• Master mold • Isopore MINs membrane
X 10000 X 10000
* Thickness of skin layer : < 6 ㎛
4) MINs membrane