DOES INORGANIC FOULING LIMIT THE USES OF ECOLOGICALLY FRIENDLY ANION EXCHANGE?

PRELIMINARY DATA

BACKGROUND

Increased water demands & diminishing high quality water

sources lead to the use of previously underutilized technologies

MOTIVATIONS

CONCLUSIONS

• The presence of calcium in solution negatively

impacts the performance of ion exchange for both

bicarbonate-form and chloride-form. The presence

of magnesium also impacts performance.

• Chloride-form ion exchange isn’t impacted as

greatly by the presence of divalent cations as

bicarbonate-form.

• Bicarbonate-form anion exchange is greatly

impacted by the presence of divalent cations. The

presence of magnesium has the most profound and

immediate impact.

• Yes, inorganic fouling does impact bicarbonate-form

ion exchange but subsequent work aims to

determine exactly how so the process can be

optimized

FUTURE WORK • Complete additional regeneration cycles and

perform regeneration cycles on waters containing

no cations, and waters containing Co2+.

• Investigate the biological fouling of bicarbonate-

form biological fouling

• Innovative regeneration by CO2(g) sparging and

optimization

Figure 1: Preliminary results showing bicarbonate-form resin

performance is on par with chloride-form in absence of divalent

cations. Synthetic water contained Santa Fe River NOM,

nitrate, sulfate, bicarbonate, and chloride. Figure adapted from

Rokicki and Boyer 20112.

Calcium

Magnesium

Figure 3: DOC removal by chloride-form ion exchange resins over

multiple regeneration cycles in the presence of calcium. Figure 4: DOC removal by bicarbonate-form ion exchange resins over

multiple regeneration cycles in the presence of calcium.

Species pKsp1

MgCO3 3.68

CaCO3 8.01

CdCO3 11.3

Figure 5: DOC removal by chloride-form ion exchange resins over

multiple regeneration cycles in the presence of magnesium.

Figure 6: DOC removal by bicarbonate-form ion exchange resins over

multiple regeneration cycles in the presence of magnesium.

ACKNOWLEDGEMENTS

I would like to thank Dr. Treavor

Boyer for all his support and

guidance. I would also like to

thank the Boyer research team

for all their help and support in

and out of the laboratory.

References 1Knovel, 2008. Knovel Critical Tables (2nd Edition). (2008).

Knovel. http://www.knovel.com/web/portal/browse/

display ?_EXT_KNOVEL_DISPLAY_bookid=761 2Rokicki, C.A., Boyer, T.H., 2011. Bicarbonate-form anion

exchange: Affinity, regeneration, and stoichiometry.

Water Research 45, 1329 -1337. 3Walker K.M., Boyer, T.H., 2011. Long-term performance of

bicarbonate-form anion exchange: Removal of dissolved

organic matter and bromide from the St. Johns River,

FL, USA.. Water Research 45 (9), 2875-2886.

RESULTS

• Ion exchange (IEX) may be a treatment

solution for certain waters with higher

levels of natural organic matter (NOM):

IEX ResinNOM

NOM

NOM

NOM

HCO3-

HCO3-

HCO3-

HCO3-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

IEX Resin

NOM

NOMNOM

NOM

HCO3-

HCO3-

HCO3-HCO3

-

Cl-

Cl-Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

• However, brine associated with chloride-

form resin limits the potential applications

of IEX. Bicarbonate-form would generate

easier to dispose of regenerant and would

prevent increase of salinity of local waters.

• It is unknown how the presence of

bicarbonate within the resin structure will

react with divalent cations:

Table 1: Carbonate mineral

solubility products. Table adapted

from Knovel 20081

IEX Resin

HCO3-

HCO3-

X2+

X2+

H+

H+HCO3-

Brine disposal is a major concern,

much like RO concentrate, it often

impedes the implementation of this

technology.

DOES INORGANIC FOULING LIMIT THE USES OF

ECOLOGICALLY FRIENDLY ANION EXCHANGE? Christopher A. Rokicki, and Treavor H. Boyer1

Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 1thboyer@ufl.edu ~ (352)846-3351 ~ http://www.ees.ufl.edu/homepp/boyer/

Figure 2: SEM images of chloride- and bicarbonate-form resin

after 14 regenerations showing inorganic fouling of bicarbonate-

form. Figure adapted from Walker and Boyer 20113.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

r0 r1 r2 r3

% D

OC

re

mo

va

l

regeneration#

M-Cl

M-HCO3

0%

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% D

OC

rem

oval

time (min)

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r3

chloride-form chloride-form

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0 50 100

% D

OC

rem

oval

time (min)

r0

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r3

bicarbonate-form

0%

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0 50 100

% D

OC

rem

oval

time (min)

r0

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r3

bicarbonate-form

0%

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0 50 100

% D

OC

rem

oval

time (min)

r0

r1

r2

r3

chloride-form

A) Changing water supply and quality

B) Advanced treatment processes needed to meet new

requirements from changes in A and demands from D

C) Waste generated in chloride-form anion exchange

needs treatment

D) Increasing water demands impact demands in B and

generates waste to be treated

E) Effluent contains trace contaminants from C

(including high TDS) and D that remain post treatment