2/17/2012
Zhaohui Li Geosciences Department, University of Wisconsin –
Parkside, Kenosha, WI 53141-2000, USA, [email protected]
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?