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8/3/2019 ED RO Pfromm 1.0
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Index1
Electrodialysis/Reverse Osmosis toRecover Dissolved Organics from
Seawater
Peter H. Pfromm, Tarl VetterDepartment of Chemical Engineering,
Kansas State UniversityManhattan, Kansas
E. Michael Perdue, Ellery Ingall,Jean-Franois Koprivnjak
School of Earth and Atmospheric SciencesGeorgia Institute of Technology
Atlanta, Georgia
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Index2
Overview
Introduction and Motivation
Electrodialysis Reverse Osmosis
Combined Process
Process Characterization Experiments/Results
Conclusions and Outlook
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Index3
Source: NASAhttp://earthobservatory.nasa.gov/Library/CarbonCycle
Units: Gigatons C, GtC/yr(1 GtC= 109 tons of carbon)
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Index4
Earth scientists would like to know: Composition of carbon reservoirs
Origin/fate of carbon reservoirs
The problem with DOC in the
oceans: Only 1 gram of carbon in 1000 liters of
seawater......
Salt
The approach: Engineers and scientists collaborate Develop a new separation approach
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Index5
What is marine dissolved organic
carbon (DOC)?
~30wt% of DOC is high molecular weight (HMW) >1000 Da
~70wt% of DOC is low molecular weight (LMW)
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Index6
How do you detect marine dissolved
organic carbon (DOC)?
Not a trivial issue: reasonably accurate part-per-billion levelanalysis for organic carbon in a high-salt (chloride) matrix.
Shimadzu TOC-VCSN high-temperature catalytic oxidationanalyzer
Sample is acidified to remove inorganic carbon, thencombusted over Pt catalyst and CO2 is detected by infrared
Many papers, book chapters, and meetings are dedicated to
this issue. Perdue at Georgia Tech is one of the well knownexperts on this.
8/3/2019 ED RO Pfromm 1.0
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35 g/L salts
~ 0.001 g/L=1 ppm DOC
Solid DOCsample
Salt
Water
Process
The issue: recover pure DOC for scientificanalysis. The problem: salt
8/3/2019 ED RO Pfromm 1.0
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State of the Art Recovery
Ultrafiltration Adsorption Methods
Pore
Tangential Flow
Water Salt LMW DOC
Salt
~30% DOC
Only recovers High Molecular WeightDOC (>1000 Da)
Salt still present in final sample
Seawater
ResinColumns
PorousNon-polar
Resin
Seawater withremaining DOC
Only recovers select species (humic, etc)
Must use pH or other method to desorb
100-300 m
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Index9
35 g/L salts
~ 1 ppm DOC
Solid DOC
sample
Salt
Water
Process
ReverseOsmosis
Electro-
dialysis
New Approach:RO removes fresh water concentrating
salt and DOC
ED removes salt with minimal loss of
uncharged species
Freeze Dry
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Index10
RO
ED The Processes
Electrodialysis Reverse Osmosis
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Index11
Electrodialysis Spacers and
Membranes
Astom AMX/CMX
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Index12
Electrodialysis
+
C C C CA A
-
Na+
Cl-
Cl-
Cl-Na+
Na+
Na+
Na+
Diluate/Feed
Diluate Return
CathodeAnode
Concentrate Return
Concentrate
+
C C C CA A
-
Na+
Cl-
Cl-
Cl-
Na+
Na+
Na+
Na+
Diluate/Feed
Diluate Return
CathodeAnode
Na+
Concentrate Return
+ -
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Index13
Electrodialysis Characterization
Limiting Current (Ilim)
0
5
10
15
20
25
30
0 10 20 30 40 50
Conductivity (mS/cm)
Limiting
CurrentDensity
(Amps)Reapp = 38
Reapp = 90
vRhapparent 4Re
LimitingCurrent(Amps)
Temperature: 25C
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Index14
RO
ED The Processes
Electrodialysis Reverse Osmosis
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Index15
Water
Salt
~ Pure Water
LowConcentration
Feed
HigherConcentration
RetentateWater Salt
Flow
High Pressure
Discarded Permeate
0.2 m
http://www.dow.com/PublishedLiterature/
Reverse Osmosis
Water
Polyesterfabric
120 m
40 mMicroporouspolysulfone
Polyamidebarrier
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Index16
Spiral Wound RO Module
http://www.purewaterplanet.com/images/ROMembrane.jpg
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Index17
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10 12 14 16 18
Conductivity (mS/cm)
Permeate
Flowrate (mL/s)
180 psi
205 psi
150 psi
120 psi
90 psi
60 psi
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 50 100 150 200
Operating Pressure (psi)
Stage Cut
0.99 mS/cm
4.11 mS/cm
7.80 mS/cm
12.12 mS/cm0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0 50 100 150 200
Operating Pressure (psi)
Stage Cut
0.99 mS/cm
4.11 mS/cm
7.80 mS/cm
12.12 mS/cm
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10 12 14 16 18
Conductivity (mS/cm)
Permeate
Flowrate (mL/s)
180 psi
205 psi
150 psi
120 psi
90 psi
60 psi
PermeateRetentate PermeateRetentate
High FeedFlow Rate
Low FeedFlow Rate
Small StageCut
Large StageCut
m
ssTCAKQ
Reverse Osmosis Characterization
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Index18
RO
Unit
ElectrodialysisStack
Combined Process Operation
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Index19
OverallDrive tosite Purge ED/ROsystems
Freeze
~10 l
Freeze dry
NMR....
Retrieve
seawatersample(200- 400 l)
ED/RO
200 l seawater
Hope for good weather!
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Index20
Experiment Date Starting Concentration (ppm) Sample Type Experimental Objective
7/12/2005 0.18 Artificial Seawater
9/28/2005 0.11 Artificial Seawater10/18/2005 0.05 Artificial Seawater
11/9/2005 0.01 Artificial Seawater
3/6/2006 0.22 Artificial Seawater
4/3/2006 0.06 Artificial Seawater
5/26/2006 1.95 Brackish Water
6/8/2006 2.24 Brackish Water
7/3/2006 3.30 Brackish Water7/18/2006 1.20 Seawater (ship board)
7/19/2006 0.93 Seawater (ship board)
7/20/2006 1.19 Seawater (ship board)
7/20, 7/21/2006 1.21 Seawater (ship board)
7/21/2006 0.82 Seawater (ship board)
7/22/2006 1.10 Seawater (ship board)
7/23/2006 0.20 Blank (ship board) Examine DOC leaching7/24, 7/25/2006 1.22 Seawater (ship board) Adjustment of ED operation
7/25, 7/26/2006 1.10 Seawater (ship board) Attempt total desalination
7/26, 7/27/2006 1.02 Seawater (ship board) Examine high concentration
7/27/2006 5.08 Brackish Water (ship board) Comparison of DOC recovery
8/14/2006 0.96 Seawater Lab reproduction of seawater
8/18/2006 1.08 Seawater Test new membranes
Determination of operating
parameters and modes
Examine recovery of natural
DOC species
Recovery of DOC from various
locations and depths
Experimentation
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Index21
Examples:
Three shipboard
experiments
Start with 200 literseawater
0
40
80
120
160
200
240
0 2 4 6
Time [hrs]
DOC
retained
[mg]ED & RO EDED
0
25
50
75
100
0 2 4 6
Time [hrs]
%
removed
ED & RO EDED
Salt
Water
ED f ll th li iti t d it
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Index22
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50
Diluate (seawater) conductivity [mS/cm]
EDcurrent
[A]
initialseawater sample
201 litersinitial ED only
RO&ED: water removalbalanced by salt removal
to maintain conductivity
limiting
current
applied
current
final ED
ED: follow the limiting current density
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Index23
0
10
20
30
40
50
60
70
80
90
100
Diluate DOC
Recovery (%)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Date of Experiment
5-26 6-8 7-3 7-18 7-19 7-20 7-21 7-21 7-22 7-24 7-25 7-26 7-27 8-14 8-18
Brackish
Seawater Lab Lab Lab Lab Lab
Summary
24
1421
21
15
21
17
1526
103
67
6
3
2
Final DOC ppm
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Index24
Conclusions ED/RO can recover a significant
fraction of DOC from seawater(60%-90%)
The process is fast, allowingtreatment of large volumes ofsamples
We are able to reduce saltconcentration and water volume tomake a sample ready for freezedrying
Preliminary results by NMR:
differences from the high MWfraction that was previouslyavailable.
Scientists and engineers thinkdifferently but can communicate
and collaborate successfully
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Index25
Outlook Examine the impact of
temperature
Further minimize losses to theED concentrate, possibly withdifferent membranes
Examine modulation of the EDcurrent to optimize DOCrecovery
Applications for recovery of
sensitive molecules (proteins,enzymes)?
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Index26
Acknowledgements
This work is supported by the National Science
Foundation, Grants No. 0425624 and 0425603.(Any opinions, findings, and conclusions or recommendations expressedin this material are those of the authors and do not necessarily reflect theviews of NSF)
Dr. Mary Rezac who initiated the contact betweenscientists and engineers that made this work
possible. Poulomi Sannigrahi for help at sea and in the
laboratory.
We would especially like to thank CaptainRaymond Sweatte and the excellent crew of theR/V Savannah for two great and productive
cruises.