1. "Advanced Membrane Materials for Water Treatment"
Thrust 2 - Desalination
"Advanced Membrane Materials for Water Treatment"
Harry Ridgway, Res. Director
Orange County Water District
Fountain Valley, California
&
Robert L. Riley, President
Separation Systems Technology
San Diego, California
Advanced Materials for
Water Purification

2. Background...
Modern water treatment is rapidly becoming dependent on membranes.
Bio-organic fouling is the major problem with the current generation of membrane separations (Example = biofouling).
Opportunities exist for innovation in the design of improved membrane materials for water purification.

3. Popular Membrane Materials...
Asymmetric
Cellulose Acetate
random, helical, non-X-linked
low flux/high salt rejection
can be biodegraded
poor organics rejection
dense, smooth, neutral surface
low fouling tendency
General Properties...
chlorine tolerant

4. Popular Membrane Materials...
Polyamide Thin-Film
Composites (TFCs)
random, X-linked
high flux/salt rejection
not biodegradable
good organics rejection
rough, charged surface
high fouling tendency
General Properties...
chlorine sensitive

5. Asymmetric CA Membrane
Cross-Flow
Feed Water
Flux
Permeate
Semipermeable
Membrane
(~0.2 micrometers)
Porous
Interior
(~0.5 mm thick)
Asymmetric CA
Membrane

6. Thin-Film Composite (TFC) Membranes...
(Polyamide Layer)

7. How are modern TFC membrane materials made?

8. + Organic Phase (Heptane, etc.) + Acid Chloride Reaction Random
COCl
Cross-Link or Extension
Diffusion N
NH2
COCl C H O
+ HCl
Reaction
Aqueous Phase
Random
Structure
NH2
Di-Functional Amine +

9. Ultrastructure of TFC Membranes...
PA Layer
PA Layer
PS Support
PS Support

10. AFM Image of
PA Surface
AFM Image of
PA Surface

11. 2. Physico-Chemical Integrity
The Issues...
-Flux loss
-Solute passage
1. Bio-organic Fouling
Molecular Adsorption
Flux & Organics Rejection 3
De-lamination PA PS 1
Swelling
2. Physico-Chemical Integrity
Chlorine Attack 2

12. The Challenge...
...is to design a new generation of advanced membrane materials having...
1. Low-fouling surfaces
2. Greater physico-chemical integrity
3. Improved flux and solute rejections

13. The Approach...
Bacteria and organics respond to a host of membrane surface properties.
A multi-variate approach is needed to identify which properties of membranes contribute to bio-organics adsorption.

14. Correlation of Membrane Surface Properties with Bacterial Attachment
(independent variables)
Multivariate Models
MLR Analysis
PC Analysis
Cluster Analysis
ANN Analysis
Bacterial
Adhesion
(dependent variable)

15. Hydrophobicity & Pore Aspect Ratio
Material Matrices...
Hydrophobicity & Pore Aspect Ratio
Flux
Thickness
Charge A D G B E H C F I
Hydrophobic
Roughness
Flux & Pore Diameter

16. SPEES-PES... Membranes Polymer B Polymer A Charged Neutral += O
CH3 C n
polysulfone (PS) 1 5
SO3H
sulfonated polyether-ethersulfone/polyethersulfone (SPEES/PES)
(sulfonation number = SPEES/PES = 1/5) +
Polymer A
Polymer B
Neutral
Charged
Knoell et al., 1999, Journal of Membrane Science

17. Bacteria Respond to Multiple Signals...
Membrane
Topology
Membrane
Hydrophobicity
Membrane
Charge
Bacterium A
(Mycobacterium)
Bacterium B
(Flavobacterium)
Knoell et al., 1999

18. Research Directions... Anti-fouling surfaces
-neutral, hydrophilic, smooth
Oxidation-resistant surfaces
-new materials (e.g., CPTC)
Enhanced flux & solute rejection
-increased cross-linking; catalytic membranes

19. Directions... Directions... Surface Modifications... -More X-linking
-smooth, hydrophilic, neutral,
mobile, renewable
-More X-linking
-Tri-amines, etc.
-Stereochemistry
-Other polymers?
Chemical
Resistance
Anti-fouling
Surfaces
Catalytic
Structural
Integrity
Directions...
Directions...
Incorporation of catalyts in membranes
Directions...
-Charged PS layer
-Fully aromatic
-Glut. X-link MPD
Directions...

20. To Increase the Hydrophilicity of TFC Surfaces...
CH2 N H ..
-OH
3-amino-1-propanol
HCl H ..
CH2 N
-OH O C =
Covalent Amide-OH O Cl C =
PA Membrane
Un-Reacted
Acid Chloride

21. To Improve Chlorine Resistance...X

22. Catalytic Membrane Materials...
Catalyst(s)
(Pd, PEIs, etc.)
N-N
CH3 = O
PA Layer
Polyester
Support
Porous PS
Pure water

23. + Mobile Membrane Surfaces... Magnetic Particles PA Layer Porous PS
Polyester
Support
Porous PS
Kishore Rajagopalan

24. (Ridgway et al. 1977. J. Bacteriol.)
Self-Assembling Renewable Surfaces...
Isolation &
Purification
Re-Assembly
Flexibacter polymorphus
a marine gliding bacterium
(Ridgway et al J. Bacteriol.)
Pore-Like Structure
Transport?
Stability?

25. Self-assembled crystalline protein-lipid arrays
Hierarchical self-assembly: 2 states of organization
Self-organization of long actin protein rods into 2D crystalline sheets
Spontaneous folding of sheets into nested tubules
Potential applications
Molecular ‘fly-paper’ for bacteria
Spontaneous entrapment of bacteria in tubules
Gerard C. L. Wong et al., Science 288, (2000)

26. Novel Materials & Processes for Water Purification
Stanford
SST
TFCs
Catalysis
ACFs, Macrocycle Gates,
Hyperbranched PEIs, etc.
UIUC
Biofilms &
Oxidation Studies
Surface-Active Materials
for Disinfection
Clark-Atlanta
Catalytic Membranes
Synergies & Collaborations...
OCWD
Surface-Modified
TFC Membranes
Biofilms
Novel Materials & Processes
for Water Purification
Surfaces, Biofilms,
Mol. Modeling & Evals.
Industry Affiliates
Pilot-Scale Studies &
Demonstrations
Applications R&D &
Evaluations
Waste Management

27. $ Expected Benefits of Research... Lower Costs of Desalination
New knowledge of
materials/interactions $
Lower Costs of
Desalination
Less pretreatment,
cleaning, downtime
More robust LF
membranes
Improved flux, rejection, efficiency, lifetime

28. Thrust #3..."Membrane Fouling
End of Thrust #2...
"Desalination"
Next Presentation...
Thrust #3..."Membrane Fouling
and Mitigation"