"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

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 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

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

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

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

How are modern TFC membrane materials made?

+ 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 +

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

AFM Image of PA Surface AFM Image of PA Surface

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

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 (independent variables) Multivariate Models MLR Analysis PC Analysis Cluster Analysis ANN Analysis Bacterial Adhesion (dependent variable)

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

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

Bacteria Respond to Multiple Signals... Membrane Topology Membrane Hydrophobicity 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

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...

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

To Improve Chlorine Resistance... X

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

+ Mobile Membrane Surfaces... Magnetic Particles PA Layer Porous PS Polyester Support Porous PS Kishore Rajagopalan [kishore@wmrc.uiuc.edu]

(Ridgway et al. 1977. J. Bacteriol.) 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)

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

$ 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

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