ed ro pfromm 1.0

8/3/2019 ED RO Pfromm 1.0

1/26

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.


7/26Index7

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


8/26Index8

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



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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



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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


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


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




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, 7/21/2006 1.21 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.

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