Synthesis of Novel Nanocomposite RED

Ion-exchange Membranes for

Salinity Gradient Power Generation2013. 11. 5

Jin Gi Hong

Georgia Institute of Technology

School of Civil and Environmental Engineering

Table of Contents

1. Current U.S. Energy Status

2. What is SGP? Potentials?

3. What is RED?

4. Advantages and Challenges of SGP (RED)

5. Nanocomposite RED Membranes

6. Synthesis of Nanocomposite RED IEMs

7. Characterizations and RED Performance

8. Future Study

Current U.S. Energy Status

Production by Energy Source

Source: International Energy Outlook 2013 (US EIA)

Consumption by Energy Source

Other

Renewable?

What is SGP? Potentials?

SGP : Salinity Gradient Power

Electrical energy generated from

inevitable entropy increase of

mixing of two solutions of different

salt concentrations [1,2]

(i.e. sea water and river water)

Estimated potential power: 2.4~2.8 TW [3,4,5]

- Current global electricity demand (i.e. ~2 TW)

- 20% world wide energy demand[6]

[1] Norman 1974, [2] Weinstein et al 1976, [3] Vermaas et al. 2011,

[4] Veerman et al. 2011, [5] Post et al. 2008, [6] Post el al. 2007.

<The Statkraft osmotic power plant, Norway>

Reverse Electrodialysis (RED)

• Reverse process of Electrodialysis

• Alternating CEMs and AEMs

between electrodes

• Salinity gradient results in a

potential difference over each

membrane.

• Chemical potential difference

causing ions to transport from

concentrated to diluted solution

• Conversion of ionic current to

electron current at the electrodes

via redox reactions

• Redox reaction is facilitated by

electrode rinse solution

• Electrical current and the potential

difference convert to electricity< A simplified schematic view of a RED stack >

RED station at Georgia Tech

Electrodialysis Stack (FT-ED-40), Fumatech, Germany

•10 FAB AEMs and 11 FKB CEMs (9×4 cm)

•Titanium mesh end electrodes coated with iridium

plasma (Anode and Cathode)

•Vertex Potentiostat/Galvanostat, Ivium Technology,

The Netherlands

•Electrochemical Impediance Spectroscopy

Advantages and Challenges

Advantages of Salinity Gradient Power

- Limitless supply (if river and the sea water is used)

- No production of pollutants (e.g. NOx)

- No CO2 exhaust, thermal pollution, radioactive waste

- No daily fluctuation in the productions due to variations in wind speed or sunshine

Technical Challenges for RED system

- Designing optimized membrane stack on large commercial scale

- Design for very low pre-filtration needs

- Extended duration test needed for real river and sea water

(fouling, stability of electrode system and etc.)

- RED optimized ion-exchange membranes are NOT available

Nanocomposite RED membranes

Optimal membrane characteristics for RED power generation

- Low electrical resistance

- High selectivity of ions (e.g., Na+ and Cl-)

- High ion-exchange capacity (IEC)

- Low swelling degree (SD)

Nanocomposite ion-exchange membranes for RED

- Incorporation of inorganic materials into organic polymer matrix

(e.g., inorganic materials: Fe2O3, SiO2, TiO2, organic materials: PPO, PES, PVA)

- Deriving optimal synergized properties by combining unique features of inorganic with

those of organic material

- Enhancing thermal and mechanical stability

Synthesis of Novel RED membranes

New type of material combination for ion-exchange membranes

o Organic polymer: poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)

- excellent membrane-forming properties (chemical, thermal, hydrolytic stability)

- high glass transition temperature (tg = 210 °C)

- low cost

- Highly hydrophilic via sulfonation

o Inorganic nanomaterials: Sulfonated iron oxide (Fe2O3 - SO42-)

- Highly proton conductive

- Strong hydrophilicity (with SO42- group)

- Large specific surface area

CH3

CH3

O

n

ClSO3H

CH3

CH3

O

HSO3 n

Research Results Obtained to Date

Morphology of NPs (Fe2O3-SO42-)

(a) Sulfonated iron oxide particles (< 50 nm )

Research Results Obtained to Date

SEM micrographs of functionalized nanoparticles

(b) Sulfonated iron oxides on membrane surface

Morphology of nanocomposite IEMs

(a) pristine, (b) 0.2 wt % Fe2O3-PPO, (c) 0.5 wt % Fe2O3-PPO, (d) 0.7 wt % Fe2O3-PPO,

(e) 1.0 wt % Fe2O3-PPO, and (f) 2.0 wt % Fe2O3-PPO, respectively.

Research Results Obtained to Date

IEM Electrochemical Properties

Optimal amount of Fe2O3-SO42- (0.5–0.7 wt%) enhanced the key electrochemical

properties

Research Results Obtained to Date

Submitted to Journal of Membrane Science (under review)

RED Stack Performance

0.7 wt% Fe2O3-SO42- achieved a maximum power density of 1.3 W/m2

(i.e., higher than that of commercially available CSO (Selemion TM, Japan) membrane)

Research Results Obtained to Date

Submitted to Journal of Membrane Science(under review)

0-Fe2O3

0.2-Fe2O3

0.5-Fe2O3

0.7-Fe2O3

1-Fe2O3

2-Fe2O3

CSO

On-going and future study

Synthesize sPPO/Fe2O3-SO42- IEMs via 2 step-phase inversion technique

- Combination of solvent evaporation and immersion precipitation

- Various membrane thicknesses

- Investigate the effect of porosity in IEM electrochemical properties and RED performance

- Investigate the effect of different thicknesses in RED performance

Synthesize and performance evaluation of novel nanocomposite IEMs using other materials

(NPs: e.g., SiO2, TiO2, CNT or graphene)

- Size variation of NPs on IEMs

- Modification of NPs for uniform dispersion on membrane surface

(e.g., HEMA (2-hydroxyethylmethacrylate)

- Variation of structural configuration in IEMs

Future Work