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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