A novel flFFF method estimating interfacial interactions related to UF and NF membrane fouling

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A novel fl-FFF method estimating interfacial
interactions related to UF and NF membrane
fouling

• Suhan Kim1,2, Sungyun Lee1, and Jaeweon Cho1,2
• 1 Department of Environmental Science and
  Engineering, GIST, Gwangju, Korea
• 2 Center for Seawater Desalination Plant,
  Gwangju, Korea

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Backgrounds (I)

• Traditional criteria for the membrane selection
  pore size and water permeability
• Fouling is an inevitable problem in membrane
  filtration processes for water reuse and
  desalination.
• Fouling occurs from interfacial interaction
  adhesion and cohesion. The parameter related to
  the interaction will be a useful index to
  estimate fouling potential.

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Backgrounds (II)

• Efforts to predict the fouling potential
  membrane and foulant characterizations
• - Membrane characterization zeta potential
  (surface charge), pore size distribution, contact
  angle (surface energy, hydrophobicity)
• - Foulant characterization size and molecular
  weight distribution, zeta potential, contact
  angle
• - Interfacial interaction model using both
  membrane and foulant characteristics

Fundamental, but laboratory-dependant (not
field-applicable) methods
(Ref) Lee et al., Desalination 202 (2006) 377.
Kim and Hoek, Desalination 202 (2006) 333.
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Backgrounds (III)

• Typical two purposes of flow field flow
  fractionation (fl-FFF)
• (1) Separation
• (2) Characterization

(Ref) Cho et el., Colloids and Surfaces A
Physicochem. Eng. Aspects 274 (2006) 43.
Tatavarty et el., Journal of Nanoscience and
Nanotechnology 6 (2006) 2461.
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Objective Hypothesis
Objective

• To develop more direct, intuitive, and
  field-friendly technique estimating fouling
  potential using fl-FFF.

Hypothesis

• If foulants are detectable, the fouling potential
  can be quantified using fl-FFF technique.
• The fouling potential by fl-FFF can be verified
  from lab-scale fouling tests.

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Theory

• Basic procedure to get the fouling potential

(A)
Larger interaction High fouling potential
(B)
Smaller interaction Low fouling potential
lt FFF results gt
(B)

• Smaller area
• Larger area

(A)
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Theory

• Membrane Performance Index (MPI) Fouling
  potential Removal efficiency

(A)
Lower PI from Higher fouling potential
(B)
Lower PI from Lower removal efficiency
(C)
Higher PI from Lower fouling potential Higher
removal efficiency
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Experimental Methods fl-FFF

• Membrane
• PW (GE Osmonics, UF)
• NE70 (Saehan, NF)
• NF90 (Dow Filmtec, NF)

• fl-FFF
• w 250 mm
• field flow rate 0.3 ml/min
• UV detector at 254 nm

• Procedure
• Injecting ? Focusing ? Operating w/ no field

No field
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Experimental Methods Fouling Test

• Foulants
• Organic matter
• HA (Humic Acid, Aldrich),
• Nanoparticle
• S120 (Silica nano particle, d120nm)
• Solutes
• NaCl 10 mM
• pH 6 (unadjusted)

• Membrane
• PW (GE Osmonics, UF)
• NE70 (Saehan, NF)
• NF90 (Dow Filmtec, NF)

• Operation conditions
• Hydrodynamic condition
• Cross-flow Re
• Cross-flow velocity m/s
• Initial flux 10 mm/s
• Temperature
• T 25?C

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Membrane Characteristics
NE70
NF90
PW
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Membrane Performance Index - S120
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S120 Fouling Test

• Salt rejection
• PW lt 1
• NE70 35
• NF90 96
• Foulant removal
• Conc. 500 mg/L
• PW 100
• NE70 100
• NF90 100

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Membrane Performance Index - HA
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HA Fouling Test

• Salt rejection
• PW lt 1
• NE70 35
• NF90 96
• Foulant removal
• Conc. 170 mg/L
• PW 96
• NE70 99.5
• NF90 99.8

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Key Findings Future works
Key findings

• A novel fl-FFF method estimating Membrane
  Performance Index (MPI) for a specific foulant
  was developed.
• MPI accounts for both fouling potential and
  removal efficiency.
• Lab-scale fouling test partially verifies MPI.

Future works

• Normalization of MPI (i.e., MPImax 1)
• More applications of MPI

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Acknowledgements

• Financial support
• This work was supported by a grant (No.
  R01-2006-000-10993-0) from the Basic Research
  Program of the Korea Science and Engineering
  Foundation (KOSEF)

• Prof. Chos research group at GIST, Korea.
• Center for Seawater Desalination Plant, Gwangju,
  Korea