A Study of the Applicability of Various Activated Persulfate Processes for the Treatment

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 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 absorbance unit * second. Experimental conditions: Temp. = 200C.

Table SI1. Review summary regarding possible 2,4-D degradation byproducts during chemical oxidation processes.

Literature / Processes / Initial 2,4-D
(mg/L) / Reaction time
(min) / Oxidant / Catalyst / Byproducts
2,4-DCP / 2,4-DCR / 4,6-DCR / 2-CHQ / 2-CBQ / CHQ / 2,4,6-TCP
1 / Photoelectro-Fenton / 100 / 300 / H2O2 / FeSO4 / ○ / ○ / ○ / ○ / ○
2 / Photoelectro-Fenton / 230 / 360 / H2O2 / FeSO4 / ○ / ○ / ○
3 / Photo-Fenton / 500 / 60 / H2O2 / FeSO4 / ○
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 / NaHSO5 / Co(AcO2)2 / ○
8 / Oxone/Co / 2,4-DCP (50) / 240 / 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), 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-DCP
2,4-Dichlororesorcinol / 2,4-DCR
4,6-Dichlororesorcinol / 4,6-DCR
2-Chlorohydroquinone / 2-CHQ
2-Chlorobenzoquinone / 2-CBQ
Chlorohydroquinone / CHQ
2,4,6-Trichlorophenol / 2,4,6-TCP

Table SI2. FMC recommended reagent dosage in the persulfate oxidation systems.

Persulfate Activation / Oxidant/Activator concentration range (M)
S2O82－ / Fe2+/EDTA / NaOH / H2O2
PS (20oC) / 0.4－1.7 / -
T-PS (70oC) / -
Fe(II)-PS / ＜2.3 / - / -
NaOH-PS / - / ＜6.3 / -
H2O2-PS / - / - / ＜2.4

Source:http://environmental.fmc.com/solutions/soil-ground-remediation/klozur-persulfate/

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
Water / 4903 / 2180 / 1303 / 2595 / 377
Water + H2O2 / 5621 / 3723 / 401 / 338 / 0
2,4-D / 168176 / 7894 / 169520 / 158109 / 163266
2,4-D + H2O2 / 74889 / 4580 / 72035 / 70100 / 69860
2,4-D + PS / 169681 / 88195 / 158140 / 89973 / 107189
Standard 6 / 156467 / 4492 / 159009 / 156842 / 155963
Standard 6 + H2O2 / 33476 / 2813 / 32248 / 29787 / 31682

(1) 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.

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.

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 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.

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Figure SI11.