Thrust 2 - Desalination"Advanced Membrane Materials

for Water Treatment"

Harry Ridgway, Res. DirectorOrange County Water District

Fountain Valley, California&

Robert L. Riley, PresidentSeparation Systems Technology

San Diego, California

Advanced Materials for Water Purification

Background...

Opportunities exist for innovation in the design of improved membrane materials for water purification.

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).

Popular Membrane Materials...

•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

Asymmetric Cellulose Acetate

Polyamide Thin-FilmComposites (TFCs)

Popular Membrane Materials...

•random, X-linked

•high flux/salt rejection

•not biodegradable

•good organics rejection

•rough, charged surface

•high fouling tendency

General Properties...

•chlorine sensitive

Cross-FlowFeed Water

SemipermeableMembrane

(~0.2 micrometers)

Asymmetric CAMembrane

Porous Interior(~0.5 mm thick)

Flux

Permeate

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

How are modern TFC membrane materials made?

Aqueous Phase

Organic Phase (Heptane, etc.)

N

NH2

COCl

C

COCl

H

O

+ HClReaction

+ Acid Chloride

COCl

COCl

COCl

Random Structure

Cross-Link or Extension Cross-Link or Extension

Cross-Link or Extension

Diffusion

NH2

NH2

Di-Functional Amine+

Ultrastructure of TFC Membranes...

PS Support

PA Layer

PS Support

PA Layer

AFM Image of PA Surface

AFM Image of PA Surface

The Issues...1. Bio-organic

Fouling

Molecular Adsorption

2. Physico-Chemical Integrity

De-lamination

PA

PS

1

-Flux loss-Solute passage

Chlorine Attack

2

Flux & Organics Rejection

3

Swelling

...is to design a new generation of advanced membrane materials having...

The Challenge...

1. Low-fouling surfaces

2. Greater physico-chemical integrity

3. Improved flux and solute rejections

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.

The Approach...

Correlation of Membrane Surface Propertieswith Bacterial Attachment

MembraneProperties

(independent variables)

BacterialAdhesion

(dependent variable)

Multivariate ModelsMLR AnalysisPC Analysis

Cluster AnalysisANN Analysis

Hydrophobicity & Pore Aspect Ratio

FluxThickness

Charge

Flux & Pore Diameter

A

D

G

B

E

H

C

F

I

HydrophobicRoughness

Material Matrices...

SPEES-PES...

Membranes

S

=

=

O

OCH3

CH3

C O O

n

polysulfone (PS)

S

=

=O

O

O

1

S

=

=

O

O

O

5

O

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

Bacteria Respond to Multiple Signals...

MembraneTopologyMembrane

Hydrophobicity Membrane Charge

Bacterium A(Mycobacterium)

Bacterium B(Flavobacterium)

Knoell et al., 1999

•Enhanced flux & solute rejection-increased cross-linking; catalytic membranes

•Anti-fouling surfaces-neutral, hydrophilic, smooth

•Oxidation-resistant surfaces-new materials (e.g., CPTC)

Research Directions...

-More X-linking-Tri-amines, etc.-Stereochemistry-Other polymers?

Incorporation of catalyts in membranes

ChemicalResistance

Anti-foulingSurfaces

CatalyticSurfacesStructural

Integrity

-Charged PS layer-Fully aromatic-Glut. X-link MPD

Surface Modifications...-smooth, hydrophilic, neutral,mobile, renewable

Directions...

Directions...Directions...

Directions...

CH2

CH2

CH2

NH H..

-OH

3-amino-1-propanol

To Increase the Hydrophilicity of TFC Surfaces...

HCl

H

..CH2

CH2

CH2

N

-OH

OC

=

Covalent Amide-OH

O ClC

=

PA Membrane

Un-ReactedAcid Chloride

To Improve Chlorine Resistance...

X X XX X

Catalytic Membrane Materials...

PA Layer

Polyester Support

Porous PS

Pure water

N-N CH 3

CH 3

=O

Catalyst(s)(Pd, PEIs, etc.)

Mobile Membrane Surfaces...

PA Layer

Polyester Support

Porous PS

Magnetic Particles

Kishore Rajagopalan [kishore@wmrc.uiuc.edu]

+

Self-Assembling Renewable Surfaces...

Isolation &Purification Re-Assembly

•Transport?•Stability?Pore-Like Structure

Flexibacter polymorphus

a marine gliding bacterium(Ridgway et al. 1977. J. Bacteriol.)

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, 2035-2039 (2000)

Novel Materials & Processesfor Water Purification

Surfaces, Biofilms,Mol. Modeling & Evals.

Surface-Active Materialsfor Disinfection

Clark-AtlantaACFs, Macrocycle Gates,Hyperbranched PEIs, etc.

UIUC

Applications R&D & Evaluations

Waste Management

Biofilms & Oxidation Studies

Industry Affiliates

Pilot-Scale Studies &Demonstrations

Stanford

SST

TFCs

Catalysis

OCWD

Surface-ModifiedTFC Membranes

Biofilms

Catalytic Membranes

Synergies & Collaborations...

$Lower Costs of Desalination

Expected Benefits of Research...New knowledge of

materials/interactions

More robust LFmembranes

Less pretreatment,cleaning, downtime

Improved flux, rejection, efficiency, lifetime

End of Thrust #2..."Desalination"

Next Presentation...Thrust #3..."Membrane Fouling

and Mitigation"