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)