2/17/2012

Zhaohui Li Geosciences Department, University of Wisconsin –

Parkside, Kenosha, WI 53141-2000, USA, li@uwp.edu

Combination of Hydrous Iron Oxide Precipitation with Zeolite Filtration to Remove Arsenic from Contaminated Water

Topic of discussion 1. Why combination of zeolite + Fe?

2. Materials and methods

3. Results

4. Instrumental characterization

5. Conclusions

6. Extension of the project

• Fe(OH)3 have strong affinity for As. • Precipitation of Fe(OH)3 from water could

remove most of dissolved As. • Filtration of As-laden Fe(OH)3 could be

achieved using sand packs. • Zeolite has higher cation exchange

capacity, thus used as cation exchanger for water treatment.

• Propose to use zeolite as filtration media

1. Why combination of zeolite + Fe?

Arsenate speciation

As(V) 0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12

Solution pH

Frac

tion

of s

peci

es

H3AsO4

H2AsO4-

AsO43-

HAsO42-

0.0

0.2

0.4

0.6

0.8

1.0

0 2 4 6 8 10 12

H3AsO3

H2AsO3-

HAsO32-

Frac

tion

of s

peci

es

Solution pH

Arsenite speciation

As(III)

pH-Eh diagram of As and Fe

⊗

⊕

GW GW

AMD AMD

2. Materials and methods

The zeolite obtained from the St. Cloud mine (Winston, NM) with a particle size range of 8-14 mesh (1.4 to 2.4 mm). Real groundwater collected from Chia-Nan Plain aquifer (SW Taiwan): Humic acid = 34 to 468 QSU (mean = 128±126.8 QSU) (quinine standard unit); ORP = -179 mV; As = 511 µg/L; neutral pH Acid mine drainage (AMD) water collected from (Chinkuashih, N Taiwan): pH = 2.9; ORP = 374 mV; FeTOT >100 mg/L; As = 147 µg/L

2. Materials and methods

Varying amounts of stock solution of As (100 mg/L) was added to DI water (178–196 mL) Varying amounts of 10 mM FeCl3·6H2O

added Solution pH raised to 7–9 by adding 1 M

NaOH Samples were analyzed for equilibrium

As and Fe concentrations

Batch studies

Each 60 mL syringe sleeve was filled with 50 mL with zeolite (about 50 g as the bulk density of zeolite is about 1 g/cm3) To 1 L of 100 or 1000 µg/L As solution, 1, 3, or 10 mL of 10 mM Fe stock was added to reach a final Fe concentration of 10, 30 and 100 μM The solution pH was raised to 7–9 by adding 1 M NaOH drop-wise before being passed through the column

Small column studies

4.5 cm in diameter and 70 cm in length 400 g of zeolite packed to a height of 28 cm 10 L of 100 µg/L As (V) synthetic arsenic

containing water 270 mg of FeCl3·6H2O added to make a final

Fe concentration of 5.6 mg/L 3.1 mL of 1 M NaOH added to raise the pH to

9.1 The mixture stirred vigorously to induce

precipitation Water passed through the column at a flow

rate about 300 mL/min

Large column studies

Samples taken every liter Real groundwater collected from Chia-Nan

Plain aquifer (SW Taiwan) Added Fe(III) equivalent to 0.2 mM, or 11.2

mg/L Acid mine drainage (AMD) water collected

from (Chinkuashih, N Taiwan) No Fe(III) added, as it contained 101 mg/L of

dissolved Fe already Only pH was raised by adding appropriate

amounts of NaOH. The flow rate between 125 and 150 mL/min

Large column studies

Small column studies

Large column studies

Sand or zeolite

FeTOT was determined using Loviband MutiDirect Photometric System (The Tintometer Ltd., Dortmund, Germany) with an analytical range of 0.02 to 1.0 mg/L

As was analyzed on either PE Optima 7000 DV ICP-OES with a detection limit of 1 µg/L or PSA Millennium System Excalibur (PS Analytical Ltd., UK) with a detection limit of 0.1 µg/L

Chemical Analyses

• pH effect on Fe concentration • pH effect on As concentration • As adsorption on Fe precipitates • Influence of Fe input on As removal • Small column tests • Tests with real water

3. Results

Fe concentration in solution

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

3 4 5 6 7 8 9 10 11 12 Solution pH

Tota

l Fe

conc

entra

tion

(mg/

L)

-3

-2

-1

0

1

3 5 7 9 11 Solution pH

log(

FeTO

T ) (m

g/L)

2nd MCL of Fe

As concentration in solution

0

200

400

600

800

1000

3 4 5 6 7 8 9 10 11 12 Solution pH

As c

once

ntra

tion

(µg/

L) As(V)

As(III)

0.0

1.0

2.0

3.0

3 4 5 6 7 8 9 10 11 12

Solution pH Lo

g (A

s) (µ

g/L)

MCL of As

Equilibrium As concentration (mg/L)

As

sorb

ed (m

g/g)

0

20

40

60

80

0.0 0.4 0.8 1.2 1.6

As(III)

As(V)

As(III) As(V)

As sorption on Fe(III) precipitates

On Raw Zeolite

Equilibrium As concentration

Initial Fe(III) concentration (mM)

As c

once

ntra

tion

(µg/

L)

As(III)

As(V)

0

4

8

12

16

0 0.2 0.4 0.6 0.8 1

Initial As concentration: 1000 µg/L

Effluent As concentration

Number of PV

As c

once

ntra

tion

(µg/

L)

[As(V)]ini= 1000 µg/L [Fe]ini = 1.0 mM

[As(V)]ini=100 µg/L [Fe]ini = 0.1 mM

0

50

100

150

0 7 14 21 28 35

Number of PV

0.0

0.1

0.2

0.3

0 7 14 21 28 35 FeTO

T co

nc. (

mg/

L)

[As(V)]ini=100 µg/L [Fe]ini = 0.1 mM

Amount of Fe Usage on As removal

Number of PVs

As

(V) c

once

ntra

tion

(μg/

L)

10 μM

100 μM

30 μM

0

20

40

60

80

0 10 20 30 40

(a)

Number of PVs

As

(III)

conc

entra

tion

(μg/

L)

0

30

60

90

120

0 10 20 30 40

10 μM

100 μM

30 μM

(b)

As and Fe concentrations Large column: 28 cm long, 4.5 cm ID, 400 g zeolite

Number of PVs

As(V

) con

cent

ratio

n (μ

g/L)

0

45

90

135

180

0 10 20 30 40 50 0.0

0.5

1.0

1.5

FeTO

T co

ncen

tratio

n (m

g/L)

As(V)

FeTOT

PV = 250 mL

Tests on real water

0.0

0.2

0.4

0.6

0 10 20 30 40 Number of PVs

As c

once

ntra

tion

(mg/

L)

AMD water effluent

Groundwater effluent

Groundwater input concentration

AMD Water input concentration

pH-Eh diagram of As and Fe

⊗

⊕

GW GW

AMD AMD

• XRD analyses to determine the mineral composition of raw zeolite and the crystalline phases of Fe precipitates

• SEM observation of the morphology of raw zeolite and the Fe precipitates and energy dispersion spectrum determination of chemical composition for Fe and As

• Mossbauer spectrum to determine the state of Fe precipitates

4. Instrumental characterization

XRD of raw zeolite

2θ (º)

Inte

nsity

(cps

)

0

200

400

600

800

1000

1200

8 13 18 23 28 33

Q F

Q

SEM observation

Euhedral clinoptilolite

Material Characterization

As

Fe

0

100

200

300

400

2 12 22 32 42 52 62 2θ (°)

Inte

nsity

(cps

)

(a) (b)

Amorphous Fe

Mössbauer spectrum

0

2000

4000

6000

8000

10000

12000

14000

16000

0 100 200 300 400 500

α-Fe

Amorphous

Removal of As from water can be achieved relatively effectively using zeolite as filtration media after HFO precipitation and As sorption onto precipitated HFO The As adsorption capacities were 48 and 68 mg/g for

As(III) and As(V) adsorption on precipitated HFO, respectively The optimal pH for maximum As removal was in

neutral range between 6.5 to 9 Depending on the initial As concentration and redox

conditions, the minimal Fe(III) need to reduce the As concentration below standard would be around 10 mg/L The method works better for waters under oxygenated

condition rather than under reduced conditions

5. Conclusions

Use of Fe-exchanged zeolite for the removal of As from water. Use of Fe-exchanged zeolite for the removal of Cr

from water

6. Extension of the project

Publications

1. Du, G., Li, Z., Hong, H., Ackley*, Leick*, S., Fenske*, N., Demarco, N. (2012) Removal of Cr(VI) from water using Fe(II)-exchanged zeolite. In preparation.

2. Du, G., Li, Z., Liao, L., Hanson*, R., MacDonald*, R., Hoeppner*, N. (2012) Influence of present Fe(III) on Cr(VI) retention and transport through natural zeolite. J. Hazard. Mater., in review.

3. Li, Z., Jiang, W.-T., Jean, J.-S., Hong, H., Liao, L., Lv, G. (2011) Combination of hydrous iron oxide precipitation with zeolite filtration to remove arsenic from contaminated water, Desalination, 280, 203-207.

4. Li, Z., Jean, J.-S., Jiang, W.-T., Chang, P.-H., Chen, C.-J., Liao, L. (2011) Removal of arsenic from water using Fe-exchanged zeolite, J. Hazard. Mater., 187, 318-323.

Acknowledgment

Funding from WI Groundwater Coordinating Council is greatly appreciated

Questions?