1. Aerogel for highly efficient solar
energy-assisted
water purification
CAROLINE PACKARD
2. Abstract
▪ International water scarcity crisis
▪ One solution: producing clean water from
seawater and wastewater
▪ Solar energy-driven water evaporation
▪ Promising technique for efficient water
purification
▪ Aerogel composed of carbon nanotubes and
hydroxyapatite nanowires
▪ Proved to have the highest performance
3. Water Scarcity &
Traditional
Techniques
▪ Water scarcity
▪ Severe threat to socioeconomic development
and human health
▪ Traditional techniques
▪ Desalination: vacuum distillation or reverse
osmosis
▪ Wastewater treatment: efficiency requires
large treatment plants
▪ High energy consumption and high cost
4. Solar Energy-
Driven Water
Evaporation
▪ Solar energy: indispensable part of Earth’s
water cycle
▪ The only reliable sources of energy in some
areas
▪ Promising technique:
▪ Low cost
▪ Easy operation
▪ Potential industrial production
▪ Minimum environmental impact
5. Ideal
Characteristics
In order to achieve evaporator optimal efficiency:
▪ Efficient sunlight absorption and energy
conversion
▪ Good thermal management capability
▪ Good insulator
▪ Hydrophilic feature
▪ High water evaporation rate
▪ High structural & chemical stability
6. Ideal
Characteristics
In order to achieve evaporator optimal efficiency:
▪ Ultralow density
▪ Able to float
▪ Ultrahigh porosity
▪ Efficiency in evaporation
▪ High water absorption performance
▪ To take in and condense maximum amount of
water
7. HAP Plus CNT
▪ Hydroxyapatite (HAP): a naturally occurring inorganic mineral
▪ High biocompatibility
▪ High thermal stability and fire resistance
▪ Ultralong HAP nanowires
▪ Previously used to make fire resistant materials
▪ Nanowires allow materials to be extremely porous,
light, and good insulators
8. HAP Plus CNT
▪ Carbon nanotubes (CNT)
▪ Integrating HAP nanowires with a CNT coating endows
unique characteristics:
▪ High sunlight absorption (black color)
▪ Ultimately, high evaporation efficiency
HAP/CNT
BILAYER
9. Experiment
Overview
GOALS
▪ To determine and optimize the efficiency of
HAP/CNT aerogel bilayer in regenerating clean
water from simulated seawater & wastewater
▪ To prove the superiority of the aerogel
versus traditional techniques or commercial
evaporators
MATERIALS
▪ Calcium oleate, rhodamine B, and other
reagents used to form the aerogel bilayer
▪ Ethanol & deionized water
▪ ”Contaminated water” containing dyes and
metal ions
10. Methods
▪ HAP nanowire synthesis:
▪ Reagents stirred and suspended in an autoclave
▪ Mixture aka slurry containing ultralong HAP nanowires
obtained
▪ HAP/CNT bilayer synthesis:
▪ HAP nanowires molded,
frozen, and freeze-dried
▪ Cylindrical sample washed
in ethanol and treated in
deionized water
▪ CNT dispersed in acetone,
then spray-coated multiple
times on top of HAP cylinder
11. Methods
▪ Steam generation
▪ Optical measurement system using solar light
simulator and power meter
▪ Surface temperature of aerogel bilayer measured
using thermal imaging camera
▪ Characterization experiments
▪ Absorption levels measured using multiple
spectrometers
▪ Thermal stability measured using
thermogravimetric analyzer
14. Thermal
Management
THERMAL STABILITY
PROPERTY
• Weight (%) versus
temperature
• After washing, no
change in weight with
increasing temperature
THERMAL INSULATION
PROPERTY
• Solar heat distribution
over 15 minutes
• Surface temperature
significantly higher,
excellent insulating
properties
15. Density &
Porosity • Porosity of HAP nanowire
aerogel = 95.26%
• Extremely porous
• Contributes to rapid
permeation and
evaporation
DENSITY & POROSITY
PROPERTIES
• Specific weight in the
aerogel’s dry state
wet state
• Wet state is
significantly heavier,
able to contain
substantial amounts
water
17. Evaporation
Efficiency
EVAPORATION
EFFICIENCY
• Mass change of the
water over time
• With aerogel, water is
evaporated very
compared to normal
evaporation
• Efficiency % decreases as
solar light power density
increases
• Due to minimal
degradation, increase in
vapor pressure, or more
heat loss
18. Steam Generation
Efficiency (Ions)
SIMULATED SEAWATER
• Concentrations of five
primary ions in from a real
seawater sample (Yellow
in China)
• Before and after solar
driven photothermal
desalination
SIMULATED WASTEWATER
• Concentrations of three kinds
of heavy metal ions found in
real wastewater
• Before and after solar
energy-driven photothermal
wastewater purification
19. Steam Generation
Efficiency (Dyes)
SIMULATED CONTAMINATED WATER
• Contains RhB-contaminated water
• After the evaporation process, the
the condensed water is nearly zero
• Meaning the water contains negligible dye
contaminant and is extremely clear
20. PRACTICAL APPLICATIONS TESTING
• Condensed water collected in
chamber
• Two pieces of HAP/CNT bilayer aerogel
diameters of 8.5 cm
• Done under outdoor solar conditions
• Results: ~51 grams of water clean water
was obtained
• Enough water for the daily drinking
requirement for two adults
• Clean as defined by the World Health
Organization standards
21. CONCLUSION
S
▪ Developed and tested a high-performance solar
energy-driven photothermal water evaporator
▪ Composed of HAP nanowire aerogel and CNT
coating layer
▪ Unique characteristics: high solar light/energy
absorption ability, low thermal conductivity, and high
porosity
▪ Extremely efficient water evaporation rate →
high-performance seawater desalination and
wastewater purification
22. Social
Applications &
Benefits
▪ In the test for practical applications:
▪ Small amount of material used
▪ In 8 hours, condensed enough water for the daily
drinking water needed for two adults
▪ More than 3 million children and 14 million women in
sub-Saharan Africa
▪ Walk 30 minutes – 8 hours every day to retrieve
contaminated water
▪ Steals time from education, employment, caring
for children
23. REFERENCES
Qin, Dong-Dong, et al. “Self-Floating Aerogel Composed
of Carbon Nanotubes and Ultralong
Hydroxyapatite Nanowires for Highly
Efficient Solar Energy-Assisted Water
Purification.” Carbon, vol. 150, 2019, pp. 233
243., doi:10.1016/j.carbon.2019.05.010.
“How Long Does It Take to Get Water? For Aysha, Eight
Hours a Day.” UNICEF USA, 1 Mar. 2018,
www.unicefusa.org/stories/how-long-does-it-take-
get-water-aysha-eight-hours-day/30776.
