Introduction of innovate membranes in water-treatment

Transcription

1 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

2 세계수자원시장전망 IPCC( 유엔국제기후변화위원회 )* 는지구온난화와엘니뇨현상으로 21 세기말지구의기온은 6.4 도, 해수면은 59Cm 상승되어물부족사태가가속화될것으로전망함. Plentiful Supply Source: UNEP/ GWI *IPCC : Intergovernment Panel on Climate Change Relatively sufficient Insufficient water Water stress Water scarcity

3 WATER TREATMENT BUSINESS Schematic Diagram for Water Treatment (Global market 2005~2015,IDA report) Agricultural : 74% Municipal : 14% Industrial : 12% : Core business segment Usage Quality of Water Source Desalination Water Treatment Surface / Ground water : 3% Seawater : 97% Wastewater Advanced WWT Reuse Treatment Conventional WWT* Water Reuse Effluent Time Sequence 수처리는사용목적에맞도록물의품질을개선시키는모든처리를말하며, 고도처리를통한 Water Reuse 는해수담수화와더불어가장빠르게확보할수있는대체수자원공급방법임 고도처리의종류에는 Membrane, UV, zone, GAC 등이있음 * WWT: Waste-Water Treatment

4 Application of Membrane Processes in Water Environment Fusion Tech Hydrology Molecular biology Surface Chem Nano particles Biofilm CFD Catalyst Space station Shower water Grey water Recreation Drinking water Industrial water Ecological water Ground water recharge

5 분리막의종류 공극크기에따른구분

6 분리막의종류 외형에따른구분 Flat sheet Hollow fiber

7 분리막을이용한수처리공정구성

8 분리막을이용한공정의대표적인문제점

9 Part 1 Conventional preparation method

10 Conventional membrane preparation Process Phase inversion by Solvent evaporation Temperature change Precipitant addition Stretching sheets of partially crystalline polymers Irradiation and etching Molding and sintering of fine-grain powders Materials Polymers: Cellulose acetate, polyamide Polypropylene, polyamide Polysulfone, nitrocellulose Polymers: PTFE Polymers: Polycarbonate, polyester Polymers: PTFE, polyethylene Source: Adapted from Ripperger and Schulz, 1986

11 Polymer used in membrane preparation Material MF UF R Cellulose esters (mixed) Cellulose nitrate Polyamide, aliphatic (e.g., Nylon) Polycarbonate (track-etch) Polyester (track-etch) Polypropylene Polytetrafluoroethylene (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 Blends Composites (e.g., polyacrylic acid on zirconia or stainless steel) Composites, polymeric thin film (e.g., PA or polyetherurea on PSF) Polybenzimidazole (PBI) Polyetherimide (PEI)

12 Sintering Schematic of the process Materials used heat Membrane pore size distribution m Porosity: 10-20% with polymers 80% with metals Powders of Polymers Powder of metals Powder of ceramics Powdre of graphite Powder of glass Polyethylene PTFE Polypropylene Stinless steel, tungsten Aluminium oxide Zirconium oxide Carbon Silicalite

13 Sintering Application of sintered membranes: Filtration of colloidal solution and suspensions Gas separation Separation of radioactive isotopes

14 Stretching Films of polyethylene or polytetrafluoroethylene are extruded at temperatures close to the T m (melting point). PTFE membrane obtained by stretching 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

15 Track-etching It is a two step process: A film is first subjected to high energy particle radiation and, then, immersed in a etching bath

16 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.

17 Phase inversion method 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 the membrane itself; A polymer lean phase, liquid, which will form the membrane pores.

18 The type of Phase inversion method There are several techniques of preparation of membranes by phase inversion, which are listed below: EIPS = Evaporation induced phase separation VIPS = Vapor induced phase separation TIPS = Temperature induced phase separation NIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation The only thermodynamic presumption for all procedures is that the system mus t have a miscibility gap over a defined concentration/temperature range What is the miscibility gap?

19 Phase diagram in binary polymer system A casting solution B membrane porosity B polymer-lean phase B polymer-rich phase binodal Polymer B Metastabile region: No precipitation, but nucleation and growth spinodal Critical point A B Liquid phase Miscibility gap B Solvent Unstable region: Phase separation Non-Solvent

20 Phase separation caused by evaporation There are several techniques of preparation of membranes by phase inversion, which are listed below: EIPS = Evaporation induced phase separation VIPS = Vapor induced phase separation TIPS = Temperature induced phase separation NIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation The only thermodynamic presumption for all procedures is that the system mu st have a miscibility gap over a defined concentration/temperature range

21 Phase separation caused by vapor There are several techniques of preparation of membranes by phase inversion, which are listed below: EIPS = Evaporation induced phase separation VIPS = Vapor induced phase separation TIPS = Temperature induced phase separation NIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation The only thermodynamic presumption for all procedures is that the system mu st have a miscibility gap over a defined concentration/temperature range

22 Thermal induced phase separation There are several techniques of preparation of membranes by phase inversion, which are listed below: EIPS = Evaporation induced phase separation VIPS = Vapor induced phase separation TIPS = Temperature induced phase separation NIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation The only thermodynamic presumption for all procedures is that the system mu st have a miscibility gap over a defined concentration/temperature range

23 Mechanism of TIPs A casting solution B membrane porosity T1 T B polymer-lean phase B polymer-rich phase A Liquid phase Unstable region: Phase separation Critical point binodal spinodal T2 B B B Metastabile region: No precipitation, but nucleation and growth Solid phase Solvent Polymer

24 Phase Inversion Method There are several techniques of preparation of membranes by phase inversion, which are listed below: EIPS = Evaporation induced phase separation VIPS = Vapor induced phase separation TIPS = Temperature induced phase separation NIPS/DIPS = Non-Solvent induced or Diffusion induced phase separation The only thermodynamic presumption for all procedures is that the system mu st have a miscibility gap over a defined concentration/temperature range

25 Phase diagram in binary polymer system Polymer Solidification Binodal Spinodal Polymer lean phase Polymer rich phase Cellular Tie line Unstable Stable Metastable Bicontinuous Solvent Nonsolvent Polymer lean phase Bead-like Polymer rich phase

26 Mechanisms L-L demixing Polymer Binodal Spinodal Unstable Non-solvent (Water) Inward diffusion N Diffusion Solvent (DMF) utward diffusion Solution(PVDF+DMF) S P Solvent Liquid-liquid de-mixing Non-solvent PDMS Polymeric solution was demixed into polymer, solvent, and nonsolvent

27 Structure of membrane prepared by PI 1) Sponge like structure 2) Finger like structure Symmetric structure Asymmetric structure Why?

28 Mechanisms membrane structure Pure water only Coagulation bath Homogeneous PVDF solution Substrate (PET film) Substrate (PET film) Finger like structure Water + solvent bath water DMF PVDF Substrate (PET film) Sponge

29 Mechanisms membrane structure Skin Formation : polymer solution gelation medium P + S [P] R >> 1 R > 1 NS R >> 1 R > 1 Defect-Free Skin Finger like structure Porous Skin Sponge like structure

30 Preparation steps- flat sheet membrane Polymer Additives Solvent 1) Preparation of the polymeric dope

31 Preparation steps flat sheet membrane 2) Casting Polymeric solution Casting knife Dense skin Support 3) Coagulation Porous support 4) membrane

32 Preparation steps-hollow fiber Polymer Additives Solvent 1) Preparation of the polymeric dope

33 Preparation steps-hollow fiber 2) Hollow fibers spinning Wet spinning Dry/wet spinning Polymeric dope Peristaltic pump Thermocouples Pressurized reservoir Bore fluid Bore fluid inlet Nascent fibre Spinneret Polymeric dope inlet N 2 Rotating coagulation bath Temperature controlling element

34 Interfacial polymerization PMMA plate Glass plate Rubber roller PMMA frame Silicone gasket 34

35 Interfacial polymerization step 1 Polysulfone support 35

36 Interfacial polymerization step 2 Trimesoyl chloride in hexane 36

37 Interfacial polymerization step 3 m-phenylene diamine aqueous solution 37

38 Interfacial polymerization step 4 Polyamide Active Layer 0.2 micron Polysulfone Support Layer 50 micron Polyester Backing Layer 150 micron

39 Commercial membranes prepared by conventional methods Membrane material cellulose acetate cellulose esters (mixed) polyacrylonitrile (PAN) polyamide (aromatic, aliphatic) polyimide polypropylene polyethersulfone polysulfone sulfonated polysulfone polyvinylidenefluoride Membrane process EP, MF, UF, R MF, D UF MF, UF, R, MC UF, R, GS MF, MD, MC UF, MF, GS, D UF, MF, GS,D UF, R, NF UF Electrophoresis (EP), Microfiltration (MF), Ultrafiltration (UF), Reverse smosis (R), 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

40 Part 2 NEW membranes to improve the performance!

41 1) Composite membrane In processes such as reverse osmosis, gas separation and pervaporation, the actual mass separation is achieved by a solution/diffusion mechanism. An asymmetric membrane structure is mandatory for these processes. Many polymers with satisfactory selectivity and permeability are not well suited for the phase inversion Composite membranes

42 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) selective layer b) porous support a) Schematic diagram of a composite membrane showing the porous support structure and the selective skin layer, and b) scanning electron micrograph of a composite membrane with polydimethylsiloxane as the selective layer on a polysulfone support structure.

43 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

44 1) Schematic diagram of composite membrane 44

45 2) Membranes prepared by block copolymer Example: High-Definition Polymeric Membranes Construction of 3D Lithographed Channel Arrays through Control of Natural Building Blocks Dynamics. The fabrication of well-defined interfaces is in high demand in many fields of biotechnologies. High-definition membrane-like arrays have been developed through the selfassembly of water droplets, which work as natural building blocks for the construction of ordered channels.

46 2) Membranes prepared by block copolymer In this work, 3D well-ordered honeycomb structures patterned from PEEK-WC-N 2 have 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

47 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!

48 3) Introducing the pattern on the membrane surface Conventional immersion precipitation method Modified immersion precipitation method Non-woven Fabric(Substrate) PDMS replica mold PVDF solution PVDF solution Non-woven Fabric(Substrate) Coagulation bath Nascent membrane PVDF membrane Coagulation bath PVDF membrane

49 3) Pyramid patterned membrane Top view 10μm

50 3) Prism patterned membrane Top view 20μm

51 3) Embossing patterned membrane Top view 20μm

52 3) Introducing the pattern on the membrane surface Prism Patterned membrane Flat membrane 1213 um Green : Cell Red : Membrane 1213 um 1213 um 1213 um

53 3) Introducing the pattern on the membrane surface

54 4) MINs membrane Si substrate PS colloidal monolayer 2 plasma by reactive ion etching (Reduced diameter of colloidal particle) HF/H 2 2 etching Si μ-pillar PS colloid lift-off Ag evaporation

55 4) MINs membrane PDMS mold Flat PDMS mold (w/o pattern) Detach PDMS mold from replica mold Master mold Replica mold (Poly(styrene-co-maleic anhydride)) Replica mold Dissolved replica mold function as adhesive between skin layer and support layer UV lamp MINs solution Pore Dissolve replica mold with toluene Casting knife MINs membrane with support layer UV curing for 2 hrs 55 Remove excess MINs with top site of pattern

56 4) MINs membrane Master mold Isopore MINs membrane X X * Thickness of skin layer : < 6 μm