enhanced performance of structured electrodialysis membranes · enhanced performance of structured...

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Enhanced performance of structured electrodialysis membranes

Harmen Zwijnenberg, Erik van de Ven, Zandrie BornemanMatthias Wessling

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Partners

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Layout

Working and limitations of bipolar electrodialysis• Bipolar Membrane Electrodialysis• Current Technological Limitations

New ED Project Approach• Nano structured polymers• Micro structured supply channels• Patents

ResultsOutlook

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++++++++++++

Bipolar Membrane Electrodialysis

ACID BASE

------------

------------

-

Cathode

++++++++++++

------------

++++++++++++

Transition region with catalyst

Bipolar membrane (BPM)

Cation selective layer Anion selective layer

H+ OH-

H2O H2O

+

Anode

X-

ACID BASE

M+ ------------

-

Cathode

-

Cathode

++++++++++++

------------

++++++++++++




H+ OH-

H2O H2O

+

Anode

+

Anode

X-

ACID BASE

M+

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Electrodialysis

ED membrane

ED spacer

ED stacks

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Limitations of Bipolar Membrane Electrodialysis

Production of base • Sensitive to scaling by carbonate deposites

Selective barrier to ions• Leakage of ions at higher concentrations

• Loss of efficiency at high concentrations

Consumes water• Drying out of membranes at high production rates

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H. Strathmann, Electrodialysis, a mature technology with a multitude of new applications, Desalination (2010),

Ion Leakage

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H. Strathmann, Electrodialysis, a mature technology with a multitude of new applications, Desalination (2010),

Efficiency Decrease

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Krol, J.J. and Jansink, M.G.J. and Wessling, M. and Strathmann, H. (1998) Behaviour of bipolar membranes at high current density. Water diffusion limitation. Separation and purification technology, 1998 (14). pp. 41-52.

Drying Out

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++++++++++++

Bipolar Membrane Electrodialysis

ACID BASE

------------

------------

-

Cathode

++++++++++++

------------

++++++++++++




H+ OH-

H2O H2O

+

Anode

X-

ACID BASE

M+ ------------

-

Cathode

-

Cathode

++++++++++++

------------

++++++++++++




H+ OH-

H2O H2O

+

Anode

+

Anode

X-

ACID BASE

M+

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New ED Focus

Nano structured polymer layers• Interpenetrating networks

• Increased functionality

• High Crosslinking density

Micro structured flow channels• Enhanced water supply

• Decreased concentration polarization

Enhanced configuration• Conductive spacers

• Turbulence promotion

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Increased cross linking density

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Increased cross linking density

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Polymer characterization

Swelling

Sulfonation degree

air water crosslinkedBatch1 3% 200% 35%Batch1a 6% 1200% 21%Batch1a 13000%

* Included glycerol, ** no crosslinking occurred

SDp-Dimethanolbenzene +ZnCl2 * 61% H+ formglycerol 67% H+ form

only heat <70% H+ formmaleic acid +ZnCl2 + TEP <70% H+ formmaleic acid +ZnCl2 + TEP ** 85% Na+ form

SD =80-85%

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Micro structured flow channels (results)

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Micro structured flow channels (patents)

Water Supply

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Micro structured flow channels (methods)

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Silicon wafer

Set screw

casting-knife

caliper

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Polymer

Polymer solution casting

SiliconNegative

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Mould layout Membrane Structure

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Wafer pattern design

Wafer pattern design

• Easy and versatile design

• Accurate dimensions

• Good release from mould

• Needs up-scaling, size = 7x7cm

• Fragile

• Clean room technology is expensive

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Large Scale micro-structured plates (via Electro Chemical Machining)

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Large Scale micro-structured plates (via Electro Chemical Machining)

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Bipolar membranes (results)

0

200

400

600

800

1000

1200

0 2 4 6 8Potential [V]

Cur

rent

Den

sity

[mA

/cm2 ]

UT SPEEK

Commercial BP

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Outlook

Optimization of layers, including catalyst optimization

Micro-structured membrane production and

characterization

Up-scaling and stress relief optimization in membrane

sheets

Integration in module concepts

Application tests in cooperation with industrial partners

enhanced performance of structured electrodialysis membranes · enhanced performance of structured...

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