CHEMISTRY
A synthetic water was formed to reproduce standard levels of
anion contaminants to test and compare the performance of MIEX-
HCO3-, which was generated for the purposes of the analysis. Once the
tests and analysis were performed Figure 9 was developed.
As shown in Figure 9, there is no decreased removal of common
anions within water sources when utilizing MIEX loaded with
bicarbonate vs. the standard chloride ion. In addition to this, the MIEX
regenerated with the 0.1M solution had no negative discernable
differences when compared to the 1.0M regenerate solution, thus
allowing for lower concentrations of chemical dosages to be used and
saving on material costs.
Innovative Ion Exchange Treatment: Process Engineering and Chemistry Considerations Jennifer N. Apell1, Chris Rokicki1, and Treavor H. Boyer1
1Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL
INTRODUCTION OBJECTIVES
ADVANTAGES
METHODS & MATERIALS
Ion exchange is a process used in water treatment to trade either positively- or negatively-
charged contaminants with the like-charged mobile counter ion that is located on the surface of the
resin. The advantage of combining cation and anion exchange in a completely mixed flow reactor
(CMFR) is that a wide range of contaminants can be removed at the beginning of the process train.
Another major benefit to using ion exchange treatment is the ability to regenerate the resin in a
concentrated solution of the mobile counter ion.
PROCESS ENGINEERING
1.) Evaluate a combined anion/cation exchange
treatment process for its ability to remove natural
organic matter and hardness.
2.) Alter the chemistry of the mobile counter ions on
the resin to provide a more efficient water treatment.
Jar testing is used in these
experiments to simulate a CMFR.
The resin is measured in slurry form
and dosed as mL of resin per L of
water. The resin is stirred 20 or 30
minutes at 100 rpm and then
allowed to settle for 30 minutes. The
sample is decanted from the jar and
used in several analyses. A diagram
of the process can be seen in
Figure 3.
•Less Waste
•Reduction of Unit Processes
•Improved treatment levels compared to standard ion
exchange treatment
•Possible use CO2 gas to regenerate resins
•More sustainable
•Save money on operating costs
-5%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
55%
60%
65%
70%
2 mL/LMIEX-Cl-
16 mL/LMIEX-Na+
Combined Sequence 1 Sequence 2 Control
Re
mo
val
DOC
Hardness
0%
10%
20%
30%
40%
50%
60%
70%
Brine Solution Acid/Base Addition
Re
mo
va
l
Hardness
4.64 1.45 1.53
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
4 mL/L 0.1M HCO3- 4 mL/L 1.0M HCO3- 4 mL/L Cl-
C/C
0
MIEX Form
Cl-
NO3-
SO42-
HCO3-
MIEX surface chemistry allows for a
variety of ions to bind to its surface. Through
regeneration methods utilizing concentrated
solutions of an ion, it is possible to load MIEX
with any of several different mobile counter ion.
The first phase of the chemistry considerations
is to explore the use of MIEX-HCO3- in order to
have a more beneficial waste effluent as
described in Figure 8.
A magnetic ion exchange resin, called MIEX, was developed by
Orica Watercare. It was created with a small particle size for easy
suspension in a CMFR, and its magnetic properties allow for the resin
to aggregate and settle at a faster rate. MIEX resin is available in both
the strong base and weak acid form.
The water treatment plant in Cedar Key, FL uses a source water
that is high in natural organic matter (NOM) and very hard (≈5.8 mg/L
as C and ≈280 mg/L as CaCO3). A combined ion exchange treatment
process would be able to reduce both concentrations in a single unit
process.
FUTURE WORK
•Measure DOC and hardness removal using
regenerated resin
•Compare different regeneration methods for
continued ability to remove hardness
•Explore the use of MIEX-HCO3- with synthetic
water dosed with natural organic matter in
addition to common anions
•Test the ability of MIEX-HCO3- to be
regenerated after being exhausted or saturated
with anions with a higher selectivity
•Test a combination of MIEX-H+ with MIEX-
HCO3- to determine the efficacy of the two in
conjunction with each other
•Test the regeneration of resin with carbon
dioxide gas
CONCLUSIONS
Based on the results of the process
engineering experiments, it is seen that using
both cation and anion treatment can remove
more NOM than anion treatment alone.
Sequencing the treatment also provides better
results than simply combining the two resins in
one CMFR. In addition, the regeneration method
used does effect the capacity of the resin.
It was also shown that MIEX-HCO3- was
able to effectively remove unwanted anions from
source water. Future tests will determine if the
combined resin treatment with the MIEX-HCO3-
will be a viable treatment method.
Preliminary experiments were conducted at several
different doses of MIEX-Cl- and MIEX-Na+ to find a dose
that could achieve approximately 50% removal. These
doses, 2 mL/L MIEX-Cl- and 16 mL/L of MIEX-Na+, were
then used concurrently and sequentially in jar tests and
compared to the removals achieved by using cation or
anion exchange alone. In Figure 4, Sequence 1 is defined
as treatment with MIEX-Cl- followed by MIEX-Na+, and
Sequence 2 is the opposite.
Fluorescence excitation emission
matrices (EEM) qualitatively show the
removal of dissolved organic matter from
the Cedar Key water. In Figure 5, the
removal of organic matter can be seen for
a) anion exchange, b) cation exchange, and
c) combined anion and cation exchange.
The EEM for the raw water in d), e), and f).
In the experiments in Figure 4, fresh resin was
used, but the cation MIEX was first loaded with Na+
by mixing the resin in a concentrated NaCl solution.
However, other procedures to load the resins are
available. For example, HCl was added to a slurry of
fresh cation resin and was then followed by the
addition of NaOH in order to load the resin with Na+.
Both resins were used in jar tests and measured for
hardness removal, which can be seen in Figure 7.
Figure 1: MIEX operation in Cedar Key, FL
Figure 2: Process train for Cedar Key, FL treatment plant
Figure 3: Experimental procedure diagram
Figure 4: Dissolved organic carbon and hardness removal
Figure 5: Fluorescence EEM of Cedar Key water that is a) MIEX-Cl- treated , b) MIEX-Na+, c) combined
MIEX-Cl- and MIEX-Na+ treated, and the fluorescence EEM for the raw water used in a), b), and c) can
be seen in d), e), and f), respectively.
Figure 6: Regeneration
methods of cation MIEX resin Figure 7: Hardness removal for resin with
different regeneration procedures
Figure 8: Regeneration of MIEX with
sodium bicarbonate or CO2 gas for an
improved waste effluent
Figure 9: C/C0 vs MIEX Form for various constituents in the water
Dissolved organic carbon, total nitrogen, and dissolved inorganic
carbon are all measured on a Shimadzu TOC-Vcph. A Hitachi U-2900
Spectrophotometer is used to measure the ultraviolet absorbance at
254nm (UV254), and a Hitachi F-2500 measures the fluorescence of
the sample. Anions (SO42-, Cl-, NO3
-) are measured using a DIONEX
ICS 3000. A hardness titration is performed according to Standard
Method 2340C.
a)
d)
b)
e)
c)
f)