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