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

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

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

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

분리막의 종류 – 공극 크기에 따른 구분

분리막의 종류 – 외형에 따른 구분

Flat sheet

Hollow fiber

분리막을 이용한 수처리 공정 구성

분리막을 이용한 공정의 대표적인 문제점

Conventional preparation method

Part 1

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

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

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

Application of sintered membranes:

Filtration of colloidal solution and suspensions

Gas separation

Separation of radioactive isotopes

Sintering

• 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

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

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

• 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

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 ?

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

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

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

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

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

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

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

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

Structure of membrane prepared by PI

1) Sponge like structure 2) Finger like structure

Why ?

Symmetric structure Asymmetric structure

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

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

1) Preparation of the polymeric dope

PolymerSolvent

Additives

Preparation steps- flat sheet membrane

Casting knifePolymeric solution

Support

2) Casting

3) Coagulation

4) membrane

Dense skin

Porous support

Preparation steps – flat sheet membrane

1) Preparation of the polymeric dope

PolymerSolvent

Additives

Preparation steps-hollow fiber

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

PMMA plate

Rubber roller

PMMA frame

Glass plate

Silicone gasket

34

Interfacial polymerization

Polysulfone support

35

Interfacial polymerization – step 1

Trimesoyl chloride in hexane

36

Interfacial polymerization – step 2

m-phenylene diamine aqueous solution

37

Interfacial polymerization – step 3

Polyamide Active Layer

Polysulfone Support Layer

Polyester Backing Layer

0.2 micron

50 micron

150 micron

Interfacial polymerization – step 4

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

NEW membranes to improvethe performance !

Part 2

• 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

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

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

44

1) Schematic diagram of composite membrane

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

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

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 !

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)

Top view

10μm

3) Pyramid patterned membrane

Top view

20μm

3) Prism patterned membrane

Top view

20μm

3) Embossing patterned membrane

Flat membrane Prism Patterned membrane

Green : CellRed : Membrane

1213 um1213 um 1213 um

1213 um

3) Introducing the pattern on the membrane surface

3) Introducing the pattern on the membrane surface

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

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

• Master mold • Isopore MINs membrane

X 10000 X 10000

* Thickness of skin layer : < 6 ㎛

4) MINs membrane