Perchlorate Ion Exchange Process using Weak Base ... - Purolite

Process Description
Under ESTCP project CU-0312, Applied Research
Associates, Inc. (ARA) and The Purolite Company
demonstrated an ion exchange process using weak base anion
(WBA) resins that are regenerable as well as perchlorateselective.
This ion exchange process takes advantage of the pH
dependent nature of WBA resins. At low pH, functional
groups on these resins have a positive charge (i.e. R-NH + 3 )
allowing for anion exchange. However, at high pH, the resin
functional groups lose a proton and are converted to the
uncharged (i.e. R-NH 2 ), "free-base" form resulting in complete
regeneration.
The ion exchange process using WBA resins is comprised of
three major operations: pretreatment, ion exchange, and post
treatment. Pretreatment consists of pH adjustment to lower
the pH of the untreated feed water so that the WBA resin is
maintained in the ionized or protonated form. Because the pH
is adjusted while under pressure, carbonate (CO 3 2- ) and
bicarbonate (HCO 3 - ) alkalinity is converted to carbonic acid.
Since carbonic acid is in equilibrium with carbon dioxide gas,
operation under pressure maintains CO 2 in solution and allows
pretreatment and ion exchange to be accomplished using a
single pumping operation. Ion exchange treatment is
conducted in conventional ion exchange vessels in lead-lag
configuration.
®
ARA is an international research
and engineering company recognized
for providing technically excellent solutions to complex and challenging
problems in the physical sciences. For detailed information about
ARA's capabilities, visit our web site at www.ara.com.
The Purolite Company is dedicated to
ION EXCHANGE RESINS
the development of ion exchange resins,
adsorbents and polymeric catalysts. Purolite is ISO 9002 certified
and has manufacturing, warehousing, application and research
facilities around the globe. For more information, visit our web
sites at www.purolite.com or www.puroliteusa.com.
Project CU-0312
Perchlorate Ion Exchange Process
using Weak Base Anion Resin
(Patent Pending)
Post treatment consists of a stripping operation and pH
control to return treated water to acceptable levels of alkalinity
and pH. The pH is controlled in the post-treatment
neutralization process by the addition of caustic. Alkalinity is
controlled by the amount of dissolved CO 2 removed prior to or
during neutralization.
Ion exchange and resin regeneration based on pH allows
protonation (anion exchange) and neutralization (regeneration)
reactions to proceed with very high chemical efficiency. Since
regeneration can be performed with an amount of caustic equal
to the equivalent amount of anions exchanged on the resin, this
approach offers a major economic advantage to strong base
resin systems, which typically require a large excess of
regenerating brine. Caustic regeneration is simple and straightforward,
and produces a small volume of spent regenerating
solution that is much easier to treat, reuse, or dispose of than
salt brine or ferric chloride-type waste from regenerating strong
base anion exchange resins. Efficient regeneration of resin and
management of water alkalinity results in very low operating
cost: $50 to $100 per acre-foot.
Contact Information:
Applied Research Associates, Inc.
430 West 5th Street, Suite 700
Panama City, FL 32401
Edward N. Coppola
850-914-3188
ecoppola@ara.com
The Purolite Company
Francis Boodoo
610-668-9090
fboodoo@puroliteusa.com
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JOINTLY DEVELOPED BY:
ION EXCHANGE RESINS

Objective
Demonstrate a novel, regenerable, perchlorate-selective ion exchange process that:
Greatly minimizes waste volume
Permits efficient waste reuse or disposal
Reduces treatment costs compared to state-of-the-art
regenerable & non-regenerable processes
Approach
Screened ion exchange resins and technologies
Selected weak base anion (WBA) technology
Developed an efficient, economical WBA treatment process
Demonstrated WBA treatment process at Redstone Arsenal
WBA Ion Exchange
Ion exchange and regeneration processes are accomplished by controlling pH
At high pH, WBA resin functional groups are in the non-ionized, free-base form
At low pH, functional groups are ionized enabling anion exchange
WBA resin in free-base form (R-NH 2 ) is ionized (R-NH 3 + ) by protonating with acid (H + ):
R-NH 2 + H + ➞ R-NH 3
+
Protonated resin removes anions (A - ) from aqueous streams:
R-NH 3
+
+ A - ➞ R-NH 3 -A
Spent resin (R-NH 3 -A) is regenerated by neutralizing with caustic (NaOH),
which liberates anions and returns resin to the free-base form:
R-NH 3 -A + Na + OH - ➞ R-NH 2 + HOH + Na + A -
WBA Ion Exchange Process (Patent Pending)
Pretreatment
Reduce pH
Acid
Treated
Water
Contaminated
Water
Ion Exchange
Conventional
Lead-Lag Equipment
Lead Ion
Exchange
Vessel
Post Treatment
Restore pH
and Alkalinity
Lag Ion
Exchange
Vessel
Bypass
Caustic
Degassing
CO2 Removal
Key Features:
Conventional lead-lag
configuration
System pressure
keeps dissolved
CO 2 in solution
Single pumping operation
Stripping excess CO 2
before neutralization
minimizes post
treatment cost
Demonstration Site: Redstone Arsenal, AL
Selected Well RS498
6-inch Extraction well
Perchlorate: 1500 to 2000 ppb
Bicarbonate: 150 ppm
Nitrate: 4 ppm
Sulfate: 3 ppm
Chloride: 4 ppm
TCE: 3100 ppb
Isotherm Results
ClO 4 Exchanged on Resin (meq/L)
110
100
90
80
70
60
Perchlorate concentration:
600 to 1500 ppb
WBA resin demonstrated:
Perchlorate selectivity
High exchange capacity
y = 45.7x + 30.4
50
0.50 0.70 0.90 1.10 1.30 1.50
ClO4 in Solution (mg/L)
Pilot System Design & Operation
Conventional lead-lag configuration
Integrated pre- and post-treatment
24 hr/day – 7 day/week operation
2-inch diameter ion exchange columns
Macroporus polystyrene divinylbenzene WBA resin
36-inch bed depth
12 to 24 bed volumes/hr treatment rate
1.5 to 3 gpm/ft 3 of resin
6 to 12 gallons/hour
Demonstration
began 6/23/05
Demonstration
completed 10/7/05
15 week test
5 test scenarios
Pilot Breakthrough Curves
Consistent with isotherm prediction
Perchlorate removal to < MDL
Effective over range of
treatment rates
Performance unaffected by
regeneration
Perchlorate (ug/L)
500
400
300
200
100
24 BV/Hour
18 BV/Hour
12 BV/Hour
Lag Columns
0
0 1000 2000 3000 4000 5000 6000 7000 8000
Water Treated (Bed Volumes)
WBA Regeneration
Successfully demonstrated three approaches
Single-pass regeneration & protonation
Batch regeneration & protonation
Batch, “zero-discharge” regeneration
& protonation
Near 100% perchlorate removal
Resin performance not affected by regeneration
No perchlorate "leakage"
No loss of treatment capacity
Zero-Discharge Regeneration
Scavenge spent regenerating and rinse
solutions with strong base anion resin
Reuse or discharge treated
regenerating and rinse solutions
O&M Cost: $5/acre-foot
for drinking water (50 ppb)
Biodegradation of
Regenerating Solution
Use existing CSTR technology
Neutralize & dilute by ~50%
Discharge treated regenerating
solution to sewer
O&M Cost: $2/kg of perchlorate
Conclusion & Comparative Cost
WBA IX process is:
Perchlorate-selective
High capacity
Regenerable
50 times more efficient
than Cl - regeneration
Zero discharge for
drinking water
Treatment Cost
per Acre-Foot
$400
$300
$200
$100
Low O&M cost: $50 to $100 per acre-foot
Single-Pass Regeneration
Clean
Water
Regen
Tank
Clean
Water
Caustic
Perchlorate
Biodegradation
System
Herington, Kansas
Caustic
Clean
Water
Caustic
Regen Rinse
Tank
Regen
Tank
Batch Regeneration
Regen
Tank
Regenerant Scavenging
Feed
Pump
Conventional
NaCl Brine
Regenerable
Ion
Exchange
Vessel
Clean
Regen
Water
Rinse Scavenging
Feed
Pump
Feed
Pump
Feed
Pump
Ion
Exchange
Vessel
Clean
Rinse
Water
Perchlorate Removal from Drinking Water
Single-Use
Disposable
Ion
Exchange
Vessel
Ion
Exchange
Vessel
WBA Resin
Regenerable
Scavenger
Resin
Vessels
Scavenger
Resin
Vessels