thrust 2 - desalination "advanced membrane materials for water treatment"
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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"
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