Transcript TDA carbon CDI electrodes are compatible with spiral - CLU-IN

:
System for Decontaminating
Well Water
for Drinking
Arsenic - Health and Remediation Applications,
Session III Webinar
April 15, 2013
TDA Research, Inc.
Girish Srinivas, Ph.D., M.B.A.
303-940-2321
[email protected]
Shawn Sapp, Ph.D.
Steve Gebhard, Ph.D., P.E.
Steve Dietz, Ph.D.
Will Spalding
Rachelle Cobb
Drew Galloway
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About TDA
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Began operations in 1987
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Privately held – 8 employee partners
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88 employees
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28 Ph.D.'s in Chemistry and Engineering
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$15 million in annual revenue
Wheat Ridge Facility
Facilities
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Combined 50,000 ft2 in Wheat Ridge and
Golden, CO
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Synthetic Chemistry
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Materials Processing & Testing
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Process Development
Business Model
Golden Facility
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Identify opportunities with industry
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Perform R&D, primarily under government
contract
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Secure intellectual property
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Commercializes technology by licensing, joint
ventures, internal business units
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TDA
Research
Outline
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Introduction/Background
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Well Water Contamination & Drinking Water
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Conventional Purification Technologies (IX, RO, sorbents/other)
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Capacitive Deionization (CDI)
Flat CDI Cell Testing
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TDA’s Activated Carbons
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Electrochemical Testing & Optimization
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Bench-Scale Prototypes, Testing, & Results
Spiral CDI Cell Testing
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Early Results
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Dual Cell Configuration
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Pre-prototype Units
Commercialization and Partnerships
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Competitive Advantages
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Market Landscape & Strategic Partnerships
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Executive Summary
• TDA has developed a capacitive deionization (CDI) process
based on
• Proprietary carbon electrodes
• Spiral wound capacitive deionization cells
• Less expensive to manufacture
• TDA has demonstrated
• Arsenic removal to below drinking water standards
• 83 ppb to < 5 ppb
• Single pass flat cell
• Currently refining the design and manufacturing method for
spiral cells
• Well water testing (spiked with arsenic)
• Real arsenic contaminated waters
• TDA partnering with ITN Energy Systems
• Develop and market PV-CDI systems
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Ground & Surface Water Contamination
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Approximately 45 million people in the U.S. (~15% of the population) get
their drinking water from wells, cisterns, or springs
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These ground and surface waters can be contaminated by local geology
or human activities
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Priority inorganic contaminants include arsenic, lead, perchlorate,
nitrate/nitrite, fluoride, etc.
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Secondary concerns include softening hard water and desalination of
briny water
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Rural and remote population sites (especially foreign)
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Some of the worst well-water quality
Conventional treatment may be
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Unavailable
Cost-prohibitive
Impractical
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Arsenic in Groundwater Worldwide
• Arsenic is a
common,
widespread
contaminant
International Groundwater Resources Assessment Centre
http://www.un-igrac.org/publications/148
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• Some areas have
very high (in red)
concentrations
Arsenic in Groundwater in the U.S.
• Areas with especially high arsenic concentrations
(50 g/L) are found in almost every state
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Chemical Forms of Aqueous Arsenic
• Many naturally
occurring and
anthropogenic sources
of arsenic in the
environment
• Sulfur is present
because Eh-pH
diagram is for waters in
contact with As rich
gold ores used to make
As2O3
• CDI removes all ionic
species, which
includes many arsenic
species
S. Wang, C.N. Mulligan, Occurrence of arsenic contamination in Canada:
3127 sources, behavior and distribution, Sci. Total Environ. 366 (2006)
701–721.
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Conventional Arsenic Removal Technologies
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Ion Exchange
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Removes ions by replacing cations with H+ and anions with OH(forming H2O)
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Requires frequent resin bed replacement (expensive) or regeneration
(time consuming)
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Can increase sodium content (e.g. home water softeners where
cations are replaced by Na+ and anions by Cl-)
Reverse Osmosis (RO)
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Requires pumping the water to high pressures (the more TDS the higher
the pressure)
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Produces water at low flow rates (poor yields)
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RO membrane modules are easily contaminated
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Module replacement is expensive and time consuming
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Sorbents/Other
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Can be low cost (e.g. activated carbon)
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Require disposal as hazardous waste or regenerated
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Ion Exchange
• Removes ions by
replacing cations with
H+ and anions with OH(forming H2O)
• Requires frequent
resin bed replacement
(expensive) or
regeneration (time
consuming)
• Some anions (e.g.
perchlorate) require
specialized resins
• Expensive
http://www.tdsmeter.com/what-is?id=0015
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Reverse Osmosis – TDS Reduction
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Reverse
Osmosis (RO)
• Requires pumping
the water to high
pressures (the
higher the pressure
the greater the
water recovery)
• Requires high
power even with
relatively clean
feeds
• Produces water at
low flow rates (at
low feed pressure)
• RO membrane
modules are easily
contaminated
• Module replacement
is expensive.
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Sorbents
Arsenic removal from water/wastewater using adsorbents—A critical review
Dinesh Mohan and Charles U. Pittman Jr.
Journal of Hazardous Materials 142 (2007) 1–53
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Capacitive Deionization (CDI)
• CDI for Decontaminating Drinking Water
• Eliminates difficult to remove ions such as arsenic (III),
perchlorate, nitrate, and other toxic inorganics
• Removes both cations and anions
• Removes charged particles
• Units small and portable
• Requires no consumables (resins, sorbents, etc.)
• Can use any DC power source (batteries, solar panels,
generators, etc.)
• Low voltage 1.2 VDC (safe); current scales with total dissolved
solids (TDS)
• Low power at typically low TDS concentrations in drinking
water
• Can deliver potable water from many sources (wells, lakes,
streams, etc.)
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Capacitive Deionization – Ion Removal
Deionization Cycle
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Cations migrate to negative electrode
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Anions migrate to positive electrode
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The required current rapidly decays as ions
are removed so it is inherently efficient and
low-power
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CDI electrostatically
removes dissolved
cations and anions from
contaminated water
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TDA CDI unit
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Stack (or spiral wound)
high surface area
carbon electrodes
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Electrodes are porous
and electrically
conductive
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Ions are removed when
DC voltage is applied
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V  1.2 volts to prevent
electrolysis of water
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Ions adsorb and are
held in the electric
double layers on the
electrodes
Electrode
Ions are Held in the Electrical Double Layer
http://www.andrew.cmu.edu/course/39801/theory/Electrical%20Double%20Layer.png
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Ions in CDI adsorb on (are
held to) the charged
electrode surfaces by
electrostatic forces (no
chemical bonding)
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IHP = Inner Helmholtz
plane is where the ions are
in direct contact with the
electrode
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OHP = Outer Helmholtz
plane is where there is
closest approach and the
ions still carry their
complement of solvating
water molecules
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Diffuse layer is transition
to bulk solution
Capacitive Deionization – Regeneration
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Electrodes are shorted
or polarity briefly
reversed to force
desorption
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Flush in reverse
direction with product
water
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Can briefly reverse polarity to speed up desorption
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Flush countercurrent with clean product water
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Stored capacitance can be re-captured during
discharge to improve efficiency (more relevant when
treating brackish water)
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Efficient because
captured salt
concentration is
highest at the inlet
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Use of product water
during flush is minimal
and resulting effluent
can be sent to the drain
Advantages of CDI
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Comparison of several
water purification
technologies
Does not require high
pressures
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Equipment and
operational costs are
reduced
Low voltages
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Safe
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Small units can be
used in remote
locations and run by
solar panels
Low power (low energy
cost)
Some of the energy can
be recovered by utilizing
stored energy (CDI is a
capacitor)
TDA’s Carbon CDI Electrodes
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TDA’s carbon electrodes
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Made using proprietary method
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Chemically pure
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Controllable pore size distribution
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Controllable surface area
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Can add surface functionality
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Testing TDA’s Carbon CDI Electrodes
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Cyclic voltammetry (CV)
• Used to determine carbon electrode
capacity for adsorbing ions
• Small static test cells
• Current response as a function of a
linearly ramped voltage
• Shape of the CV trace gives the
resistance & capacitance properties
of the cell
• Electrode capacitance is calculated
from the current and scan rate
• Varying the voltage scan rate
enables kinetic measurements
• Both rate and capacitance must be
optimized for ideal cell performance
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Optimum Electrode Thickness 6 mil
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Cyclic voltammetry
between ±1.2 V at very
slow and very fast scan
rates
Peak capacitance vs. scan
rate plots allow for
comparison between
carbon materials
Plot shows the data for
optimizing the thickness of
our carbon electrodes
Data show that 6 mil (0.006”
~ 0.15 mm) is optimal
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TDA Carbon Electrodes are Redox Inactive
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Platinum electrode
exhibits reductionoxidation (redox)
chemistry with 100 ppm
lead, Pb2+ from Pb(NO3)2
No current transients
present using TDA
carbon electrode
indicating good chemical
stability
Ions can be removed
without chemical
reactions occurring using
TDA’s carbon CDI
electrodes
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Long Term Stability of TDA’s Carbon CDI Electrodes
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Cyclic voltammetry used to measure long
term stability by subjecting electrodes to
thousands of cycles
Break-In
(rapid cell
improvement)
Hard water, 394 mg/L as Ca(CO3)2
Slow, 25 mV/s scan rate to simulate slow
rate of charge and discharge during CDI
TDA carbon CDI electrodes exhibit an
initial break-in period followed by
gradually improving performance
Performance still slowly improving even
after 6,000 cycles
Same test done with well water
contaminated with 100 ppm Pb2+ which is
6,700 times EPA drinking water limit
Very small decrease in capacitance was
observed (less than 0.04% drop, per
100,000 cycles, per ppb of lead)
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Approaching
Steady-State
(continued
improvement)
Early Testing with Flat/Stacked Plate CDI Cells
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Typical Flat Cell Construction
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Flow Paths in Early Flat Cell Designs
Serpentine
Flow Cell
Side-View of
Stack Layers
Parallel
Flow Cell
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Hybrid Flat Cell Design
Hybrid (Parallel/Serpentine) Flow Cell
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Typical Flat Cell Performance
Hard Well Water
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A real-world, sample of very hard
water, 394 mg/L as Ca(CO3)2 ,
was used to demonstrate basic
CDI performance
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Data show the results of a singlepass through a parallel flow, flat
plate cell with water analysis
before and after treatment
A standard break-in period of 6-8
cycles is typical for this type of
cell, so the data are displayed for
inlet the 14th cycle
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Contaminated Well Water Testing
• Hard well water
contaminated with
• 54 ppb perchlorate
(ClO4-)
Hybrid Flat Cell
• 66 ppm nitrate (NO3-)
• 25 ppb lead (Pb2+)
• 83 ppb arsenic (III)
(AsO2-)
• Concentration of all
contaminates reduce to
levels well below EPA
drinking water
standards
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Hybrid Flat Cell:
Contaminated Well Water Performance
Much better than
low pressure RO
which is typically
~10% efficient
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TDA Spiral Wound CDI Module Technology
• Flat electrodes
• Satisfactory for testing
the effects of
• Thickness
• Pore size distribution
• Surface area
• Too expensive to
manufacture
• All current CDI systems
use flat electrodes
• There are no spiral
wound CDI modules
currently in use
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TDA Spiral Wound Design – Early Prototype
• Spiral wound CDI cells have been fabricated with a factor of 4x
improvement in surface/volume ratio over “plate-type” cells
• 1st Generation of spiral wound cell has typical removal
efficiency of ~80% with simple saline feeds (500 ppm NaCl)
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Spiral Wound Design – Stacked Modules
• Two Pyrex glass “spool piece”
bodies (4”dia x 4” long)
• Electrodes, spacers, current
collectors, insulators rolled into
a cylinder and inserted into the
glass
• Units are then sealed and
top/bottom clamped in place
• Electrical connections made to
metal tabs
• Can be used individually or
stacked (as shown)
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Single vs. Stacked Modules
• As expected,
stacking the two
cell modules
improves
performance
Carbon #1
single
Carbon #2
single
• Simulates using
several spiral
wound modules
in series
Carbon #2 two
stacked
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Pre-Prototype Units
• Electrodes 11 inches wide
(instead of 4 in)
• Cells still 4 inch diameter
• Both Pyrex glass and PVC
housings tested
• Easier to see leaks and
other problems with glass
unit
• Designing 1 gal/hr
prototype units
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Spiral Cell Electrode Winding Machine
• Previously used hand
winding to roll spiral
cells
• Winding machine
recently built in-house
at TDA
• Greater tension
• Improves alignment at
ends
• Better reproducibility
• Better scalability
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Strategic Partnerships – ITN
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ITN Power Systems, Inc. (ITN, Littleton, CO) develops green energy and storage
technology for today’s and tomorrow’s needs. Areas of core competency include:
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Energy generation & storage devices
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Sensors & actuators
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Separation membranes
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Flexible, thin film electronic device structures
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Nanotechnology
In 2005, ITN spun off Ascent Solar who manufactures cutting-edge solar technology
(CIGS & thin film PV) that easily integrates into a wide range of products and
applications. Areas of core competency include:
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Custom turnkey PV systems
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Building-integrated PV
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Flexible CIGS modules
Ascent Solar flexible PV panels
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Portability & Low Power
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Some domestic and many foreign
population centers
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Need water decontamination systems
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Less likely to have a well developed
power or water treatment
infrastructure
Portability and low power are
essential requirements
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CDI modules are inherently compact;
spiral wound cells reduce size by at
least a factor of four and are cheaper
to manufacture
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No consumables, sorbents, chemicals
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Power requirements are well below
existing portable RO systems (ITN)
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PV-battery powered systems practical
500 gal/day, field-portable, PV-powered, RO
module built & tested by ITN
TDA has partnered with ITN to
develop PV/battery powered CDI
modules
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ITN- Partnership
• Work with ITN to build a PV unit and interface it with
TDA’s prototype CDI system
• PV-CDI system will be tested on
• Well water spiked with contaminants
• Actual arsenic contaminated waters
• ITN has strategic partnerships in Asia
• ITN proposes to license (non-exclusive) TDA’s spiral
wound CDI cell technology worldwide
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Competitive Advantages
• TDA’s carbons are cost competitive with Kuraray &
MeadWestvaco activated carbons (≤ $10/kg)
• TDA electrodes long lasting, which reduces overall carbon cost
per 1000 gal of water treated
• TDA electrodes are chemically pure carbon (no contaminants
from the carbon)
• TDA electrode carbons can be optimized for improved
performance
• Electrode production is easily scaled up (continuous process)
• TDA carbon CDI electrodes are compatible with spiral wound cell
designs which dramatically decreases manufacturing costs
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Business Environment
• Drinking water market driven by:
• Low cost for water treatment
• Health regulations
• Portability (especially military field use)
• Remote applications (powered using solar cells)
• Competing technologies (ion exchange and
reverse osmosis)
• Reverse Osmosis is power intensive (pumping water to
high pressure)
• Ion exchange requires expensive (and logistically
inconvenient) media replacement or refill reagents
• CDI is low power and has no expendables
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Conclusions
• TDA has developed a capacitive deionization process based on
• Proprietary carbons
• Spiral CDI cells
• Less expensive to manufacture
• TDA has demonstrated
• Arsenic removal to below drinking water standards
• 83 ppb to < 5 ppb
• Single pass flat cell
• Currently refining the design and manufacturing method for
spiral cells
• Well water testing (arsenic spiked)
• Real arsenic contaminated waters
• TDA partnering ITN Energy Systems
• Develop and market PV-CDI systems
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Acknowledgments
• National Institute of Environmental Health Sciences (NIEHS)
• U.S. Department of Energy (DOE)
• ITN Energy Systems
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