Supporting Information
A Study of the Applicability of Various Activated Persulfate Processes for the
Treatment of 2,4-Dichlorophenoxyacetic Acid
Contents
Table SI1. Review summary regarding possible 2,4-D degradation byproducts during
chemical oxidation processes.
Table SI2. FMC recommended reagent dosage in the persulfate oxidation systems.
Table SI3. CO2 Readings from TOC analyzer under different analytical modes.
Figure SI1. HPLC chromatography showing 2,4-D degradation and intermediate
byproducts evolution as a function of time under 200C persulfate
activation (PS). Numbers of 1, 2, and 3 represent three major byproducts
observed at retention times (RT) 3.175, 5.458, and 10.602 min,
respectively. PS represents a PS peak and I.S. represents an internal
standard peak.
Figure SI2. HPLC chromatography showing 2,4-D degradation and intermediate
byproducts evolution as a function of time under hydrogen peroxide
persulfate activation (H2O2-PS). Numbers of 1, 2, and 3 represent three
major byproducts observed at retention times (RT) 3.175, 5.458, and
10.602 min, respectively. PS represents a PS peak and I.S. represents an
internal standard peak.
Figure SI3. HPLC chromatography showing 2,4-D degradation and intermediate
byproducts evolution as a function of time under sodium hydroxide
persulfate activation (NaOH-PS). Numbers of 1, 2, and 3 represent three
major byproducts observed at retention times (RT) 3.175, 5.458, and
10.602 min, respectively. PS represents a PS peak and I.S. represents an
internal standard peak.
Figure SI4. HPLC chromatography showing 2,4-D degradation and intermediate
byproducts evolution as a function of time under ferrous ion persulfate
activation (Fe(II)-PS). Numbers of 4 and 5 represent two major
1
byproducts observed at retention times (RT) 5.317 and 5.726 min,
respectively. PS represents a PS peak.
Figure SI5. HPLC chromatography showing 2,4-D degradation and intermediate
byproducts evolution as a function of time under 700C persulfate
activation (T-PS). Numbers of 1 and 2 represent two major byproducts
observed at retention times (RT) 3.175 and 5.458 min, respectively. PS
represents a PS peak and I.S. represents an internal standard peak.
Figure SI6. HPLC chromatography showing 2,4-Dichlorophenol analysis using
HPLC method #1. (a) water only sample; (b) 2,4-Dichlorophenol sample
(0.307 mM).
Figure SI7. HPLC chromatography showing 2,4-Dichlorophenol analysis using
HPLC method #2. (a) water only sample; (b) 2,4-Dichlorophenol sample
(0.307 mM); (c) Fe(II)-PS experiment (reaction time = 1 hr). Numbers
of 4 and 5 represent two major byproducts observed at retention times (RT)
5.317 and 5.726 min, respectively. PS represents a PS peak.
Figure SI8. Persulfate and hydrogen peroxide decomposition as a function under
various persulfate activations. Experimental conditions: Temp. = 20oC
(except for T-PS system Temp. = 70oC) and fixed [PS] = 100 mM; [H2O2]
= 300 mM; [NaOH] = 50 mM; [Fe] = 10 mM.
Figure SI9. Total iron and ferrous ion concentrations as a function of time during iron
activated persulfate reaction. Experimental conditions: Temp. = 20oC;
[Fe] = 10 mM and [PS] = 100 mM.
Figure SI10. 2,4-D degradation byproduct formation as a function of time for
experiments of iron activated persulfate oxidation under various ferrous
ion concentrations. Fe2+/S2O82- molar ratios of (a) 20/100, (b)10/100,
(c)5/100, (d)1/100, and (e)0.5/100。Note: Quantities of byproducts are
measured using HPLC/UV detector responses, i.e., mAU*s: mili
absorbance unit * second. Experimental conditions: Temp. = 200C.
Figure SI11. 2,4-D degradation byproduct formation as a function of time for
experiments of iron activated persulfate oxidation under various persulfate
concentrations. Fe2+/S2O82- molar ratios of (a) 10/100, (b)5/100,
(c)10/10, (d)5/5, (e)10/5, and (f)5/2.5。Note: Quantities of byproducts are
measured using HPLC/UV detector responses, i.e., mAU*s: mili
2
absorbance unit * second. Experimental conditions: Temp. = 200C.
3
Table SI1. Review summary regarding possible 2,4-D degradation byproducts during chemical oxidation processes.
Reaction
time
(min)
Byproducts
Oxidant
Catalyst
Literature
Processes
Initial 2,4-D
(mg/L)
1
Photoelectro-Fenton
100
300
H2O2
FeSO4
○
2
Photoelectro-Fenton
230
360
H2O2
FeSO4
○
3
Photo-Fenton
500
60
H2O2
FeSO4
2,4-DCP 2,4-DCR 4,6-DCR 2-CHQ 2-CBQ CHQ 2,4,6-TCP
○
○
○
○
○
○
○
Fe2(SO4)3
4
Sono-electrochemical
55-332
10
H2O2
FeSO4
○
5
AOP review based on
hydroxyl radical
－
－
－
－
○
6
O3/UV/TiO2
10
120
O3
TiO2
○
7
PMS/Co
100
45
8
Oxone/Co
2,4-DCP
(50)
240
NaHSO5 Co(AcO2)2
Oxone
CoCl2
○
○
○
○
○
○
References:
1. Badellino, C.; Rodrigues, C.; Bertazzoli, R., Oxidation of herbicides by in situ synthesized hydrogen peroxide and fenton’s reagent in an
electrochemical flow reactor: study of the degradation of 2,4-dichlorophenoxyacetic acid. Journal of Applied Electrochemistry 2007, 37 (4),
451-459.
2. Brillas, E.; Calpe, J. C.; Casado, J., Mineralization of 2,4-D by advanced electrochemical oxidation processes. Water Research 2000, 34 (8),
4
2253-2262.
3. Kwan, C. Y.; Chu, W., Photodegradation of 2,4-dichlorophenoxyacetic acid in various iron-mediated oxidation systems. Water Research
2003, 37 (18), 4405-4412.
4. Yasman, Y.; Bulatov, V.; Gridin, V. V.; Agur, S.; Galil, N.; Armon, R.; Schechter, I., A new sono-electrochemical method for enhanced
detoxification of hydrophilic chloroorganic pollutants in water. Ultrasonics Sonochemistry 2004, 11 (6), 365-372.
5. Peller, J.; Wiest, O.; Kamat, P. V., Hydroxyl Radical's Role in the Remediation of a Common Herbicide, 2,4-Dichlorophenoxyacetic Acid
(2,4-D). The Journal of Physical Chemistry A 2004, 108 (50), 10925-10933.
6. Giri, R. R.; Ozaki, H.; Takanami, R.; Taniguchi, S., A novel use of TiO2 fiber for photocatalytic ozonation of 2,4-dichlorophenoxyacetic
acid in aqueous solution. Journal of Environmental Sciences 2008, 20 (9), 1138-1145.
7. Bandala, E. R.; Peláez, M. A.; Dionysiou, D. D.; Gelover, S.; Garcia, J.; Macías, D., Degradation of 2,4-dichlorophenoxyacetic acid (2,4-D)
using cobalt-peroxymonosulfate in Fenton-like process. Journal of Photochemistry and Photobiology A: Chemistry 2007, 186 (2-3), 357-363.
8. Anipsitakis, G. P.; Dionysiou, D. D.; Gonzalez, M. A., Cobalt-Mediated Activation of Peroxymonosulfate and Sulfate Radical Attack on
Phenolic Compounds. Implications of Chloride Ions. Environmental Science & Technology 2005, 40 (3), 1000-1007.
Possible byproduct
acronym
2,4-Dichlorophenol
2,4-Dichlororesorcinol
4,6-Dichlororesorcinol
2-Chlorohydroquinone
2-Chlorobenzoquinone
Chlorohydroquinone
2,4-DCP
2,4-DCR
4,6-DCR
2-CHQ
2-CBQ
CHQ
2,4,6-Trichlorophenol
2,4,6-TCP
5
Table SI2. FMC recommended reagent dosage in the persulfate oxidation systems.
Persulfate
Activation
Oxidant/Activator concentration range (M)
S2O82－
Fe2+/EDTA
NaOH
PS (20oC)
-
T-PS (70oC)
-
H2O2
＜2.3
-
-
NaOH-PS
-
＜6.3
-
H2O2-PS
-
-
＜2.4
Fe(II)-PS
0.4－1.7
Source:http://environmental.fmc.com/solutions/soil-ground-remediation/klozur-persulfate/
6
Table SI3. CO2 Readings from TOC analyzer under different analytical modes.
Samples(1)
TC
TIC only
NPOC
only(2)
TIC &
NPOC(2)
TC-TIC
(TOC)(2)
Signal reading
(1)
Water
Water + H2O2
2,4-D
2,4-D + H2O2
2,4-D + PS
Standard 6
4903
5621
168176
74889
169681
156467
2180
3723
7894
4580
88195
4492
1303
401
169520
72035
158140
159009
2595
338
158109
70100
89973
156842
377
0
163266
69860
107189
155963
Standard 6 + H2O2
33476
2813
32248
29787
31682
Standard 6 (KHP) concentration = 40 ppm C; 2,4-D concentration = 0.452 mM (43 ppm C);
Hydrogen peroxide = 300 mM; PS = 100 mM
(2)
When samples contained PS, phosphoric acid was added to react with TIC and heated to 70oC to
expel CO2 from solution in all analytic modes, except TC mode. At these cases, thermally activated
persulfate would oxidize organics and result in higher TIC signal readings of CO2. Therefore,
subsequent TOC readings would be lower than true values.
Note:
 TC (total carbon) includes TOC (total organic carbon) and TIC (total inorganic
carbon); TOC includes POC (purgeable organic carbon) and NPOC (non purgeable
organic carbon); NPOC includes DOC (dissolved organic carbon) and SOC
(suspended organic carbon).
 All samples were filtered through 0.2 µm filter and analyzed using DOC mode in this
study.
7
1
2
3
Figure
SI1. HPLC chromatography showing 2,4-D degradation and intermediate byproducts evolution as a
function of time under 200C persulfate activation (PS). Numbers of 1, 2, and 3 represent three
major byproducts observed at retention times (RT) 3.175, 5.458, and 10.602 min, respectively. PS
represents a PS peak and I.S. represents an internal standard peak.
8
1
2
3
Figure SI2. HPLC chromatography showing 2,4-D degradation and intermediate byproducts
evolution as a function of time under hydrogen peroxide persulfate activation (H2O2-PS). Numbers
of 1, 2, and 3 represent three major byproducts observed at retention times (RT) 3.175, 5.458, and
10.602 min, respectively.
PS represents a PS peak and I.S. represents an internal standard peak.
9
1
2
3
Figure SI3. HPLC chromatography showing 2,4-D degradation and intermediate byproducts
evolution as a function of time under sodium hydroxide persulfate activation (NaOH-PS). Numbers
of 1, 2, and 3 represent three major byproducts observed at retention times (RT) 3.175, 5.458, and
10.602 min, respectively.
PS represents a PS peak and I.S. represents an internal standard peak.
10
4
5
Figure SI4. HPLC chromatography showing 2,4-D degradation and intermediate byproducts
evolution as a function of time under ferrous ion persulfate activation (Fe(II)-PS). Numbers of 4
and 5 represent two major byproducts observed at retention times (RT) 5.317 and 5.726 min,
respectively. PS represents a PS peak.
11
1
2
Figure SI5. HPLC chromatography showing 2,4-D degradation and intermediate byproducts
evolution as a function of time under 700C persulfate activation (T-PS). Numbers of 1 and 2
represent two major byproducts observed at retention timesS (RT) 3.175 and 5.458 min, respectively.
PS represents a PS peak and I.S. represents an internal standard peak.
12
Figure SI6. HPLC chromatography showing 2,4-Dichlorophenol analysis using HPLC method #1.
(a) water only sample; (b) 2,4-Dichlorophenol sample (0.307 mM).
13
4
2,4-DCP
5
Figure SI7. HPLC chromatography showing 2,4-Dichlorophenol analysis using HPLC method #2.
(a) water only sample; (b) 2,4-Dichlorophenol sample (0.307 mM); (c) Fe(II)-PS experiment
(reaction time = 1 hr).
Numbers of 4 and 5 represent two major byproducts observed at retention
times (RT) 5.317 and 5.726 min, respectively. PS represents a PS peak.
14
1.0
2,4-D (C/C0)
0.8
Activation
PS
HPPS
SHPS
FePS
HPS
0.6
0.4
Control
o
(2,4-D at 20 C)
(2,4-D+H2O2)
(2,4-D+NaOH)
2+
(2,4-D+Fe )
o
(2,4-D at 70 C)
0.2
0.0
1.0
DOC (C/C0)
0.8
0.6
0.4
0.2
0.0
1.0
PS or H2O2 (C/C0)
0.8
H2O2 (HPPS)
0.6
0.4
PS (HPPS)
0.2
0.0
0
24
48
72
96
120
144
168
192
216
240
Time (hr)
Figure SI8. Persulfate and hydrogen peroxide decomposition as a function under various persulfate
activations.
Experimental conditions: Temp. = 20oC (except for T-PS system Temp. = 70oC) and
fixed [PS] = 100 mM; [H2O2] = 300 mM; [NaOH] = 50 mM; [Fe] = 10 mM.
15
10
FeT
2+
FeT and Fe (mM)
8
Fe
2+
Control
FePS
6
4
2
0
0
6
12
18
24
30
36
42
48
Time (hr)
Figure SI9. Total iron and ferrous ion concentrations as a function of time during iron activated
persulfate reaction. Experimental conditions: Temp. = 20oC; [Fe] = 10 mM and [PS] = 100 mM.
16
0.5
(a)
2,4-D
byproduct 4 (5.317 min)
byproduct 5 (5.726 min)
2,4-D (mM)
100
0.2
50
0.1
0
6
12
18
24
30
36
42
48
150
0.3
100
0.2
50
0.1
0
0.0
0
6
12
18
Time (hr)
0.5
0.5
(c)
36
42
48
(d)
200
0
200
0.4
50
0.1
0
6
12
18
24
30
36
42
48
2,4-D (mM)
100
0.2
150
100
0.2
50
0.1
0
0.0
Time (hr)
0.5
0.3
0
6
12
18
24
30
36
42
48
byproduct (mAU*s)
0.3
byproduct (mAU*s)
150
2,4-D (mM)
30
Time (hr)
0.4
0.0
24
byproduct (mAU*s)
150
0.3
0.0
200
0.4
byproduct (mAU*s)
0.4
(b)
200
2,4-D (mM)
0.5
0
Time (hr)
(e)
200
0.4
2,4-D (mM)
100
0.2
50
0.1
0.0
0
6
12
18
24
30
36
42
48
byproduct (mAU*s)
150
0.3
0
Time (hr)
Figure SI10. 2,4-D degradation byproduct formation as a function of time for experiments of iron
activated persulfate oxidation under various ferrous ion concentrations.
Fe2+/S2O82- molar ratios of
(a) 20/100, (b)10/100, (c)5/100, (d)1/100, and (e)0.5/100。Note: Quantities of byproducts are
measured using HPLC/UV detector responses, i.e., mAU*s: mili absorbance unit * second.
Experimental conditions: Temp. = 200C
17
(a)
200
0.2
100
0.0
0
6
12
18
24
30
36
42
48
300
0.3
200
0.2
100
0.1
0.0
0
0
6
12
18
0.2
100
0.1
12
18
24
30
36
42
300
200
0.2
100
0.1
0.0
400
0.5
0
6
12
18
0.2
100
0.1
18
24
30
36
42
48
0
36
42
48
400
(f)
0.4
2,4-D (mM)
2,4-D (mM)
200
12
30
300
0.3
200
0.2
100
0.1
0
0.0
0
Time (hr)
6
12
18
24
30
36
42
48
byproduct (mAU*s)
0.3
byproduct (mAU*s)
300
6
24
Time (hr)
0.4
0
0
400
(d)
Time (hr)
0.0
48
0.3
0
48
(e)
0.5
42
0.4
2,4-D (mM)
2,4-D (mM)
200
6
36
byproduct (mAU*s)
0.3
byproduct (mAU*s)
300
0
0.5
400
(c)
0.4
0.0
30
Time (hr)
Time (hr)
0.5
24
byproduct (mAU*s)
0.3
0.1
400
(b)
0.4
300
byproduct (mAU*s)
2,4-D (mM)
0.4
0.5
400
2,4-D
byproduct 4 (5.317 min)
byproduct 5 (5.726 min)
2,4-D (mM)
0.5
0
Time (hr)
Figure SI11.
Figure SI11. 2,4-D degradation byproduct formation as a function of time for experiments of iron
activated persulfate oxidation under various persulfate concentrations. Fe2+/S2O82- molar ratios of
(a) 10/100, (b)5/100, (c)10/10, (d)5/5, (e)10/5, and (f)5/2.5。Note: Quantities of byproducts are
measured using HPLC/UV detector responses, i.e., mAU*s: mili absorbance unit * second.
Experimental conditions: Temp. = 200C
18