Transcript TDA carbon CDI electrodes are compatible with spiral - CLU-IN
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 28 Ph.D.'s in Chemistry and Engineering $15 million in annual revenue Facilities
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Combined 50,000 ft 2 Golden, CO in Wheat Ridge and
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Synthetic Chemistry Materials Processing & Testing
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Process Development Business Model
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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 Commercializes technology by licensing, joint ventures, internal business units
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Wheat Ridge Facility Golden Facility TDA R e s e a r c h
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) Capacitive Deionization (CDI) Flat CDI Cell Testing
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TDA’s Activated Carbons Electrochemical Testing & Optimization Bench-Scale Prototypes, Testing, & Results Spiral CDI Cell Testing
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Early Results Dual Cell Configuration Pre-prototype Units Commercialization and Partnerships
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Competitive Advantages Market Landscape & Strategic Partnerships
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Executive Summary
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TDA has developed a capacitive deionization (CDI) process based on
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Proprietary carbon electrodes
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Spiral wound capacitive deionization cells Less expensive to manufacture TDA has demonstrated
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Arsenic removal to below drinking water standards
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83 ppb to < 5 ppb Single pass flat cell Currently refining the design and manufacturing method for spiral cells
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Well water testing (spiked with arsenic) Real arsenic contaminated waters TDA partnering with ITN Energy Systems
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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 These ground and surface waters can be contaminated by local geology or human activities Priority inorganic contaminants include arsenic , lead, perchlorate, nitrate/nitrite, fluoride, etc.
Secondary concerns include softening hard water and desalination of briny water
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Rural and remote population sites (especially foreign) 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
International Groundwater Resources Assessment Centre http://www.un-igrac.org/publications/148 6 • •
Arsenic is a common, widespread contaminant Some areas have very high (in red ) concentrations
Arsenic in Groundwater in the U.S.
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Areas with especially high arsenic concentrations (
50
g/L) are found in almost every state
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Chemical Forms of Aqueous Arsenic
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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 As 2 O 3 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, 701 –721.
Sci. Total Environ. 366 (2006) 8
Conventional Arsenic Removal Technologies
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Ion Exchange Removes ions by replacing cations with H + (forming H 2 O) and anions with OH Requires frequent resin bed replacement (expensive) or regeneration (time consuming) Can increase sodium content (e.g. home water softeners where cations are replaced by Na + and anions by Cl ) Reverse Osmosis (RO) Requires pumping the water to high pressures (the more TDS the higher the pressure) Produces water at low flow rates (poor yields) RO membrane modules are easily contaminated Module replacement is expensive and time consuming Sorbents/Other Can be low cost (e.g. activated carbon) Require disposal as hazardous waste or regenerated
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Ion Exchange
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Removes ions by replacing cations with H + and anions with OH (forming H 2 O) 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 10
Reverse Osmosis – TDS Reduction
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Reverse Osmosis (RO)
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Requires pumping the water to high pressures (the higher the pressure the greater the water recovery)
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Requires high power feeds even with relatively clean
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Produces water at low flow rates (at low feed pressure)
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RO membrane modules are easily contaminated
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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 12
Capacitive Deionization (CDI)
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CDI for Decontaminating Drinking Water
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Eliminates difficult to remove ions such as arsenic (III), perchlorate, nitrate, and other toxic inorganics
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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.)
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Low voltage 1.2 VDC (safe); current scales with total dissolved solids (TDS)
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Low power at typically low TDS concentrations in drinking water
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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 Anions migrate to positive electrode 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 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
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Ions are Held in the Electrical Double Layer
http://www.andrew.cmu.edu/course/39 801/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) IHP = Inner Helmholtz plane is where the ions are in direct contact with the electrode OHP = Outer Helmholtz plane is where there is closest approach and the ions still carry their complement of solvating water molecules Diffuse layer is transition to bulk solution
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Capacitive Deionization – Regeneration
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Electrodes are shorted or polarity briefly reversed to force desorption Can briefly reverse polarity to speed up desorption 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) Flush in reverse direction with product 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
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Advantages of CDI
Comparison of several water purification technologies
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Does not require high pressures
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Equipment and operational costs are reduced Low voltages
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Safe Low power (low energy cost)
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Small units can be used in remote locations and run by solar panels Some of the energy can be recovered by utilizing stored energy (CDI is a capacitor)
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TDA’s Carbon CDI Electrodes
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TDA’s carbon electrodes Made using proprietary method
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Chemically pure Controllable pore size distribution
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Controllable surface area Can add surface functionality
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Testing TDA’s Carbon CDI Electrodes
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Cyclic voltammetry (CV)
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Used to determine carbon electrode capacity for adsorbing ions
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Small static test cells
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Current response as a function of a linearly ramped voltage
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Shape of the CV trace gives the resistance & capacitance properties of the cell
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Electrode capacitance is calculated from the current and scan rate
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Varying the voltage scan rate enables kinetic measurements
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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 reduction oxidation (redox) chemistry with 100 ppm lead, Pb 2+ from Pb(NO 3 ) 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 Hard water, 394 mg/L as Ca(CO 3 ) 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 Pb 2+ 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) Break-In (rapid cell improvement) Approaching Steady-State (continued improvement)
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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(CO 3 ) 2 , was used to demonstrate basic CDI performance Data show the results of a single pass 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 14 th cycle
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Contaminated Well Water Testing
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Hard well water contaminated with
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54 ppb perchlorate (ClO 4 ) 66 ppm nitrate (NO 3 ) 25 ppb lead (Pb 2+ ) 83 ppb arsenic (III) (AsO 2 ) Concentration of all contaminates reduce to levels well below EPA drinking water standards Hybrid Flat Cell
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Hybrid Flat Cell: Contaminated Well Water Performance
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Much better than low pressure RO which is typically ~10% efficient
TDA Spiral Wound CDI Module Technology
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Flat electrodes
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Satisfactory for testing the effects of
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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
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Spiral wound CDI cells have been fabricated with a factor of 4x improvement in surface/volume ratio over “plate-type” cells 1 st 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
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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
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As expected, stacking the two cell modules improves performance
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Simulates using several spiral wound modules in series
Carbon #1 single Carbon #2 single Carbon #2 two stacked 33
Pre-Prototype Units
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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
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Previously used hand winding to roll spiral cells Winding machine recently built in-house at TDA
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Greater tension
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Improves alignment at ends
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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 Sensors & actuators Separation membranes Flexible, thin film electronic device structures Nanotechnology
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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 Building-integrated PV Flexible CIGS modules
Ascent Solar flexible PV panels 36
Portability & Low Power
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Some domestic and many foreign population centers
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Need water decontamination systems 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 Power requirements are well below existing portable RO systems (ITN)
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PV-battery powered systems practical TDA has partnered with ITN to develop PV/battery powered CDI modules 500 gal/day, field-portable, PV-powered, RO module built & tested by ITN
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ITN- Partnership
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Work with ITN to build a PV unit and interface it with TDA’s prototype CDI system PV-CDI system will be tested on
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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
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TDA’s carbons are cost competitive with Kuraray & MeadWestvaco activated carbons (≤ $10/kg)
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TDA electrodes long lasting, which reduces overall carbon cost per 1000 gal of water treated
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TDA electrodes are chemically pure carbon (no contaminants from the carbon)
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TDA electrode carbons can be optimized for improved performance
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Electrode production is easily scaled up (continuous process)
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TDA carbon CDI electrodes are compatible with spiral wound cell designs which dramatically decreases manufacturing costs
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Business Environment
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Drinking water market driven by:
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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)
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Reverse Osmosis is power intensive (pumping water to high pressure)
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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
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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
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Develop and market PV-CDI systems
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Acknowledgments
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National Institute of Environmental Health Sciences (NIEHS) U.S. Department of Energy (DOE) ITN Energy Systems
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