Transcript Document
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
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.
Popular Membrane Materials...
Asymmetric Cellulose Acetate
General Properties...
•random, helical, non-X-linked •dense, smooth, neutral surface •low flux/high salt rejection •poor organics rejection •chlorine tolerant •low fouling tendency •can be biodegraded
Popular Membrane Materials...
Polyamide Thin-Film Composites (TFCs)
General Properties...
•random, X-linked •rough, charged surface •high flux/salt rejection •good organics rejection •chlorine sensitive •high fouling tendency •not biodegradable
Feed Water Porous Interior (~0.5 mm thick) Flux Cross-Flow Semipermeable Membrane (~0.2 micrometers) Asymmetric CA Membrane Permeate
Thin-Film Composite (TFC) Membranes...
(Polyamide Layer)
How are modern TFC membrane materials made?
Diffusion
Organic Phase (Heptane, etc.) + Acid Chloride Cross-Link or Extension Cross-Link or Extension
Reaction
O H + HCl Cross-Link or Extension Random Structure Aqueous Phase + Di-Functional Amine
Ultrastructure of TFC Membranes...
PA Layer PA Layer PS Support PS Support
AFM Image of PA Surface AFM Image of PA Surface
The Issues...
-Flux loss -Solute passage 1. Bio-organic Fouling Molecular Adsorption De-lamination 2. Physico Chemical Integrity 1
PA PS
2 Chlorine Attack Flux & Organics Rejection 3 Swelling
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
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.
Correlation of Membrane Surface Properties with Bacterial Attachment
Membrane Properties (independent variables)
Multivariate Models
MLR Analysis PC Analysis Cluster Analysis ANN Analysis Bacterial Adhesion (dependent variable)
Material Matrices...
Hydrophobicity & Pore Aspect Ratio Flux Thickness Charge A D G B E H Flux & Pore Diameter C I F Hydrophobic Roughness
SPEES-PES...
Polymer A CH 3 C CH 3 O O S O polysulfone (PS) Neutral O n + Polymer B O SO 3 H O O O S O S O 1 O sulfonated polyether-ethersulfone/polyethersulfone (SPEES/PES) (sulfonation number = SPEES/PES = 1/5) Charged 5
Membranes
Knoell et al., 1999, Journal of Membrane Science
Bacteria Respond to Multiple Signals...
Membrane Hydrophobicity Membrane Topology Membrane Charge
Bacterium A (Mycobacterium) Bacterium B (Flavobacterium)
Knoell et al., 1999
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
-More X-linking -Tri-amines,
etc.
-Stereochemistry -Other polymers?
Directions...
Surface Modifications...
-smooth, hydrophilic, neutral, mobile, renewable
Anti-fouling Surfaces Chemical Resistance
Directions...
Catalytic Structural Integrity Surfaces
Directions...
-Charged PS layer -Fully aromatic -Glut. X-link MPD
Directions...
Incorporation of catalyts in membranes
To Increase the Hydrophilicity of TFC Surfaces...
3-amino-1 propanol
H -OH CH 2 CH 2 CH 2 H
Covalent Amide-OH Un-Reacted Acid Chloride
O C Cl O C -OH CH 2 CH 2 CH 2 N H HCl
PA Membrane
To Improve Chlorine Resistance...
X X X X X
Catalytic Membrane Materials...
Catalyst(s) (Pd, PEIs, etc.)
PA Layer Porous PS Polyester Support Pure water
+
Mobile Membrane Surfaces...
Magnetic Particles PA Layer Porous PS Polyester Support Kishore Rajagopalan [[email protected]]
Self-Assembling Renewable Surfaces...
Isolation & Purification Re-Assembly Flexibacter polymorphus a marine gliding bacterium
(Ridgway et al. 1977. J. Bacteriol.)
Pore-Like Structure •Transport?
•Stability?
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)
Stanford UIUC Catalysis Catalytic Membranes Clark-Atlanta ACFs, Macrocycle Gates, Hyperbranched PEIs, etc.
TFCs SST Biofilms & Oxidation Studies Surface-Active Materials
Synergies & Collaborations...
Novel Materials & Processes for Water Purification
Surface-Modified TFC Membranes Applications R&D & Evaluations Surfaces, Biofilms, Mol. Modeling & Evals.
Pilot-Scale Studies & Demonstrations Biofilms Waste Management OCWD Industry Affiliates
Expected Benefits of Research...
New knowledge of materials/interactions Less pretreatment, cleaning, downtime
Lower Costs of Desalination
More robust LF membranes Improved flux, rejection, efficiency, lifetime