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BaSO4 Precipitation:
Motivation and Goal
Stoichiometry: Dissolved Organic Carbon (DOC):
Results
The goal of this research is to understand
interactions between NOM and divalent cations
during cation exchange processes in order to
enhance ion exchange reactions for
pretreatment to NF or RO membrane
technologies.
Future Work
A very special thanks to Weizhi Chang and Troy Chasteen for their help and support in the lab, and ESPECIALLY
to Dr. Boyer and the research group!
Methods
Table 1. Composition of synthetic waters
pH 7-8
DOC 5 mg/L
SO42- 50 mg/L
Alkalinity 125 mg/L as CaCO3
Hardness:
Ca2+ Hardness 250 mg/L as CaCO3
Ca2+/ Mg2+ Hardness 250 mg/L as CaCO3
Mg2+ Hardness 250 mg/L as CaCO3
No Hardness 0 mg/L as CaCO3
NOM Isolate:
SR NOM, STMR NOM, No NOM
R-Na
Ca2+
Hardness
Mg2+
Hardness
Ca2+/Mg2+
Hardness
No Hardness
R2-Ca
Ca2+
Hardness
Mg2+
Hardness
Ca2+/Mg2+
Hardness
No Hardness
R2-Mg
Ca2+
Hardness
Mg2+
Hardness
Ca2+/Mg2+
Hardness
No Hardness
R2-Sr
Ca2+
Hardness
Mg2+
Hardness
Ca2+/Mg2+
Hardness
No Hardness
R2-Ba
Ca2+
Hardness
Mg2+
Hardness
Ca2+/Mg2+
Hardness
No Hardness
Figure 2. Organization of cation
exchange experiments
0.0
5
0.0
3
0.0
3
0.0
6
0.0
3
0.0
3
0.0
7
0.0
3
0.0
3
0.6
2
0.3
3
1.0
1
0.0
0.2
0.4
0.6
0.8
1.0
MIEX-Ba (SR NOM) MIEX-Ba (No NOM) C106Na-Ba (SR NOM)
C/C
o
Sulfate Removed (Barium form of ion exchange resin)
Ca Hardness
Ca/Mg Hardness
MgHardness
No Hardness
Figure 5. Sulfate removal for cation exchange
resins with barium as the mobile counter ion
(reflects precipitation of barium sulfate)
Combined Ion Exchange Pretreatment to Reduce Membrane Fouling:
Understanding Fundamental Chemistry During Ion Exchange Reactions Katie Indarawis, Treavor H. Boyer
Department of Environmental Engineering Sciences, University of Florida [email protected] ♦ 352-281-5369 ♦ Follow our research group on twitter! @WaterWeUpTo
Na+
Na+
Na+
Na+
Na+
Na+
Na+ Na+
Na+
- - - - - - - - -
-
- -
-
Figure 1. Interactive schematic of cation
exchange reaction
•DOC is removed with MIEX by NOM adsorption onto
exposed iron oxide from resin
•More DOC is removed with STMR NOM than SR NOM in
the presence of divalent cations, although they have similar
charge density. Most likely due to steric arrangement of
functional groups on NOM.
•NOM adsorption onto exposed iron oxide hinders
barium release from resin. Possible NOM-Ba+
complexes formed.
• When barium is released (hardness waters), BaSO4
precipitates and NOM either coprecipitates with it or
adsorbs onto the surface of the precipitate.
•Compare DOC removal and stoichiometry of the sodium form of the resin and chloride form of the resin to DOC removal
and stoichiometry of combining both the sodium and chloride forms of the resins in one reactor.
•Conduct bench-scale nanofiltration experiments with ion exchange as a pretreatment: anion pretreatment, cation
pretreatment, combined cation and anion pretreatment and no pretreatment.
•Repeat bench-scale NF experiments with the most effective pre-treatment process on membrane concentrate as an
intermediate treatment before cycling that water through the NF membrane.
•Repeat most effective treatment train with multiple regenerations of ion exchange resin.
0.0
0.2
0.4
0.6
0.8
1.0
MIEX-Na MIEX-Ca MIEX-Mg MIEX-Sr MIEX-Ba
C/C
o
DOC Removed (magnetic resin - SR NOM)
Ca Hardness
Ca/Mg Hardness
MgHardness
No Hardness
0.0
0.2
0.4
0.6
0.8
1.0
C106Na-Na C106Na-Ca C106Na-Mg C106Na-Sr C106Na-Ba
C/C
o
DOC Removed (non-magnetic resin - SR NOM)
Ca Hardness
Ca/Mg Hardness
MgHardness
No Hardness
0.0
0.2
0.4
0.6
0.8
1.0
MIEX-Na MIEX-Ca MIEX-Mg
C/C
o
DOC Removed (magnetic resin - STMR NOM)
Ca Hardness
Ca/Mg Hardness
MgHardness
No Hardness
NOM fouling + Divalent cation
scaling (with complexation)
Membrane Membrane
Complexed
species
Divalent cation scaling
Membrane Membrane
Divalent
cations
NOM fouling
Membrane Membrane
NOM
Figure 3. DOC removal for SR NOM and STMR NOM
with various experimental conditions
NOM-
Ba2+ SO42-
SO42-
Ba2+
NOM-
NOM-
BaSO4
Coprecipitation Adsorption
vs.
Alternative
water
sources
Membrane
Technologies
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4
To
tal C
ati
on
s R
em
ov
ed
(m
eq
/L)
Total Cations Released (meq/L)
R-Na
Ca Hardness (SR NOM)
Ca Hardness
Mg/Ca Hardness (SR NOM)
Mg/Ca Hardness
Mg Hardness (SR NOM)
Mg Hardness
No Hardness (SR NOM)
No Hardness
Linear (y=x line) 0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4
To
tal C
ati
on
s R
em
ov
ed
(m
eq
/L)
Total Cations Released (meq/L)
R2-Ca
Ca Hardness (SR NOM)
Ca Hardness
Mg/Ca Hardness (SR NOM)
Mg/Ca Hardness
Mg Hardness (SR NOM)
Mg Hardness
No Hardness (SR NOM)
No Hardness
Linear (y=x line)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4
To
tal C
ati
on
s R
em
ov
ed
(m
eq
/L)
Total Cations Released (meq/L)
R2-Mg
Ca Hardness (SR NOM)
Ca Hardness
Mg/Ca Hardness (SR NOM)
Mg/Ca Hardness
Mg Hardness (SR NOM)
Mg Hardness
No Hardness (SR NOM)
No Hardness
Linear (y=x line) 0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4
To
tal C
ati
on
s R
em
ov
ed
(m
eq
/L)
Total Cations Released (meq/L)
R2-Sr
Ca Hardness (SR NOM)
Ca Hardness
Mg/Ca Hardness (SR NOM)
Mg/Ca Hardness
Mg Hardness (SR NOM)
Mg Hardness
No Hardness (SR NOM)
No Hardness
Linear (y=x line)
0
0.5
1
1.5
2
2.5
3
3.5
4
0 2 4
To
tal C
ati
on
s R
em
ov
ed
(m
eq
/L)
Total Cations Released (meq/L)
R2-Ba
Ca Hardness (SR NOM)
Ca Hardness
Mg/Ca Hardness (SR NOM)
Mg/Ca Hardness
Mg Hardness (SR NOM)
Mg Hardness
No Hardness (SR NOM)
No Hardness
Linear (y=x line)
Figure 4. Stoichiometry during cation exchange for various
experimental conditions
•Expected results, but different behaviors between the different
forms of the cation exchange resin.
•More barium removed, reflecting precipitation.
