1. 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
katrinas@ufl.edu ♦ 352-281-5369 ♦ Follow our research group on twitter! @WaterWeUpTo
Motivation and Goal NOM Divalent Complexed The goal of this research is to understand
species
cations interactions between NOM and divalent cations
during cation exchange processes in order to
Alternative Membrane Membrane
Membrane Membrane Membrane enhance ion exchange reactions for
water Membrane Membrane
Technologies NOM fouling + Divalent cation pretreatment to NF or RO membrane
sources
NOM fouling Divalent cation scaling scaling (with complexation) technologies.
Methods Results
Dissolved Organic Carbon (DOC): Stoichiometry: BaSO4 Precipitation:
Na+ Na+
Na+
- - -- DOC Removed
R-Na R2-Ca Sulfate Removed
- 4 4 (Barium form of ion exchange resin)
Total Cations Removed
Total Cations Removed
Ca Hardness (SR NOM) Ca Hardness (SR NOM)
- (magnetic resin - SR NOM) 3.5 3.5
-
Ca Hardness Ca Hardness
1.01
Na+ 1.0
3 Mg/Ca Hardness (SR NOM) 3 Mg/Ca Hardness (SR NOM)
-- - - 2.5 2.5 1.0 Ca Hardness
(meq/L)
(meq/L)
Mg/Ca Hardness Mg/Ca Hardness
2 Mg Hardness (SR NOM) 2 Mg Hardness (SR NOM)
Ca/Mg Hardness
Na+
Na+
-- Na+
0.8 1.5
1
Mg Hardness
No Hardness (SR NOM)
1.5
1
Mg Hardness
No Hardness (SR NOM)
0.8 MgHardness
0.62
0.5 No Hardness 0.5 No Hardness No Hardness
Na+ Na+ 0.6 Ca Hardness 0 0
C/Co
C/Co
Linear (y=x line) Linear (y=x line)
0.6
Ca/Mg Hardness 0 2 4 0 2 4
Total Cations Released (meq/L) Total Cations Released (meq/L)
0.4 MgHardness
0.33
0.4
No Hardness
0.2 R2-Mg R2-Sr
4 4 0.2
0.07
0.06
0.05
Total Cations Removed
Total Cations Removed
Ca Hardness (SR NOM) Ca Hardness (SR NOM)
0.03
0.03
0.03
0.03
0.03
0.03
3.5 Ca Hardness 3.5 Ca Hardness
0.0 3 3
Mg/Ca Hardness (SR NOM) Mg/Ca Hardness (SR NOM)
0.0
MIEX-Na MIEX-Ca MIEX-Mg MIEX-Sr MIEX-Ba 2.5 2.5
(meq/L)
(meq/L)
Mg/Ca Hardness Mg/Ca Hardness
2 2
MIEX-Ba (SR NOM) MIEX-Ba (No NOM) C106Na-Ba (SR NOM)
Mg Hardness (SR NOM) Mg Hardness (SR NOM)
Figure 1. Interactive schematic of cation DOC Removed 1.5
1
Mg Hardness
No Hardness (SR NOM)
1.5
1
Mg Hardness
No Hardness (SR NOM) Figure 5. Sulfate removal for cation exchange
exchange reaction (non-magnetic resin - SR NOM) 0.5 No Hardness 0.5 No Hardness
0 Linear (y=x line) 0 Linear (y=x line) resins with barium as the mobile counter ion
0 2 4 0 2 4
1.0
Total Cations Released (meq/L) Total Cations Released (meq/L)
(reflects precipitation of barium sulfate)
NOM Isolate:
0.8
SR NOM, STMR NOM, No NOM
R2-Ba
Ca Hardness •NOM adsorption onto exposed iron oxide hinders
C/Co
0.6 4
Ca/Mg Hardness
Total Cations Removed
Ca Hardness (SR NOM)
R-Na R2-Ca R2-Mg R2-Sr R2-Ba MgHardness
3.5 Ca Hardness barium release from resin. Possible NOM-Ba+
0.4 3 Mg/Ca Hardness (SR NOM)
No Hardness 2.5 complexes formed.
(meq/L)
Mg/Ca Hardness
• When barium is released (hardness waters), BaSO4
Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ 2 Mg Hardness (SR NOM)
Hardness Hardness Hardness Hardness Hardness
0.2
1.5 Mg Hardness
1
0.0 0.5
No Hardness (SR NOM)
No Hardness
precipitates and NOM either coprecipitates with it or
Mg2+ Mg2+ Mg2+ Mg2+ Mg2+
Hardness Hardness Hardness Hardness Hardness C106Na-Na C106Na-Ca C106Na-Mg C106Na-Sr C106Na-Ba 0 Linear (y=x line)
adsorbs onto the surface of the precipitate.
0 2 4
Total Cations Released (meq/L)
Ca2+/Mg2+ Ca2+/Mg2+ Ca2+/Mg2+ Ca2+/Mg2+ Ca2+/Mg2+ DOC Removed
Hardness Hardness Hardness Hardness Hardness (magnetic resin - STMR NOM)
1.0 Figure 4. Stoichiometry during cation exchange for various NOM- Ba2+ NOM-
No No No No No
Hardness Hardness Hardness Hardness Hardness
0.8
experimental conditions Ba2+ SO42- vs.
BaSO4
SO42- NOM-
Figure 2. Organization of cation 0.6 Ca Hardness
•Expected results, but different behaviors between the different
C/Co
exchange experiments Ca/Mg Hardness forms of the cation exchange resin. Coprecipitation Adsorption
0.4 MgHardness •More barium removed, reflecting precipitation.
No Hardness
0.2
Table 1. Composition of synthetic waters
pH 7-8
0.0 Future Work
MIEX-Na MIEX-Ca MIEX-Mg
DOC 5 mg/L
Figure 3. DOC removal for SR NOM and STMR NOM •Compare DOC removal and stoichiometry of the sodium form of the resin and chloride form of the resin to DOC removal
SO42- 50 mg/L with various experimental conditions and stoichiometry of combining both the sodium and chloride forms of the resins in one reactor.
Alkalinity 125 mg/L as CaCO3
•Conduct bench-scale nanofiltration experiments with ion exchange as a pretreatment: anion pretreatment, cation
•DOC is removed with MIEX by NOM adsorption onto pretreatment, combined cation and anion pretreatment and no pretreatment.
Hardness:
exposed iron oxide from resin •Repeat bench-scale NF experiments with the most effective pre-treatment process on membrane concentrate as an
 Ca2+ Hardness 250 mg/L as CaCO3
intermediate treatment before cycling that water through the NF membrane.
•More DOC is removed with STMR NOM than SR NOM in
 Ca2+/ Mg2+ Hardness 250 mg/L as CaCO3
the presence of divalent cations, although they have similar •Repeat most effective treatment train with multiple regenerations of ion exchange resin.
 Mg2+ Hardness 250 mg/L as CaCO3 charge density. Most likely due to steric arrangement of A very special thanks to Weizhi Chang and Troy Chasteen for their help and support in the lab, and ESPECIALLY
 No Hardness 0 mg/L as CaCO3 functional groups on NOM. to Dr. Boyer and the research group!