The Degradation Kinetics of Typical EDCs (Endocrine Disruption

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on January 7, 2017 | http://pubs.acs.org Publication Date (Web): December 19, 2016 | doi: 10.1021/bk-2016-1238.ch013

Chapter 13

The Degradation Kinetics of Typical EDCs (Endocrine Disruption Chemicals) by Ferrate(VI) Cong Li* and Feilong Dong* College of civil engineering and architecture, Zhejiang University, Hangzhou 310027, China *E-mail: [email protected]; [email protected]

The aqueous reactivity of five prominent endocrine disrupting chemicals(EDCs) with ferrate(VI) were investigated. The rate constants for 17α-ethynylestradiol (EE2), estrone (E1), bisphenol A (BPA), β-estradiol (E2) and estriol (E3) have been determined and compared by the kinetic models incorporating the various species for EDCs compounds and ferrate(VI). Comparing with different kinetic models, the oxidation of the EDCs was found to be greater for protonated ferrate, HFeO4-, than for non-protonated ferrate.

Introduction Ferrate(VI) is an emerging water treatment chemical due to its dual functions as an oxidant and a subsequent coagulant/precipitant (1, 2). Ferrate(VI) can oxidize and reduce sulfur- and nitrogen-containing compounds (e.g., hydrogen sulfide and hydrazine), phenols, amines and alcohols (1, 2). As the result of its combined oxidant and coagulant effects, ferrate(VI) has been demonstrated to be quite effective in removing arsenic and copper(I) cyanide from water (3, 4). In addition, ferrate(VI) has been known to react via one electron or two electrons transfer depending on its reaction counterparts. As an example of one electron transfer, the oxidation of phenol by ferrate(VI) was proposed to produce phenoxyl radicals and ferrate(V) through a hydrogen abstraction mechanism (5). A two electron transfer mechanism was suggested for the oxidation of sulfite by ferrate(VI) through a direct oxygen transfer mechanism, generating sulfate and ferrate(IV). Ferrate(V) and ferrate(IV) were known to be several orders of © 2016 American Chemical Society Sharma et al.; Ferrites and Ferrates: Chemistry and Applications in Sustainable Energy and Environmental Remediation ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


magnitude more reactive than ferrate(VI) (6, 7). Therefore, oxidation rates of pollutants by ferrate(VI) may be enhanced when reactions are conducted in the presence of one electron or two electron reducing substrates. In recent years, there has been increasing concern about the widespread occurrence of endocrine-disrupting chemicals (EDCs). EDCs were released into aquatic environments as a result of industrial and agricultural, which had been found in sewage at concentrations in the nanogram per liter (8). This study has considered to research the degradation kinetics of five EDCs by ferrate(VI), bisphenol A (BPA), 17 a-ethynylestradiol (EE2), estrone (E1), 17 b-estradiol (E2), and estriol (E3), which have been chosen for their environmental significance. And their structures and properties were showed in Table 1.

Table 1. Elementary Physicochemical Property of selected ECDs

338 Sharma et al.; Ferrites and Ferrates: Chemistry and Applications in Sustainable Energy and Environmental Remediation ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

Material and Methods Chemicals and Reagents


The ferrate(VI) was prepared in the laboratory with high purity (99%) by a previously optimized method based on the oxidation of ferric nitrate with hypochlorite as shown in Figure 1 (9). The selected EDCs were all obtained from Sigma Aldrich. The solution were prepared with water passed through a Milli-Q system with resistivity >18 MΩ.

Figure 1. Ferrate(VI) prepared

Potassium Ferrate Preparation Firstly, 37% HCl was reacted with KMnO4 to produce chlorine. Secondly, the chlorine was added to KOH solution (60 g of KOH in 100 ml of water) and the resulting suspension was cooled. Thirdly, the yellow solution of KClO was reacted with Fe(NO3)3•9H2O when the precipitate of KCl was removed. Last, the ferrate(III) ion was oxidized to ferrate(VI) and the solution became dark purple (9).



Analytical Equipment and Methods The typical EDCs were determined using high-perfomance liquid chromatography (HPLC, P4000) with UV detector (UV 6000 LP) (10). The ferrate(VI) concentrations were determined using the ABTS method at 415 nm. Potassium ferrate solutions ([Fe(VI)]0=0.05–0.5 mM) and EDC compounds ([BPA]0=0.1 mM, [E1]0=0.01 mM, [E2]0=0.01 mM, [E3]0=0.01 mM and [EE2]0=0.01 mM) were prepared with deionized water. The oxidation experiments were carried out in the beaker with pH range of 8–12. Then samples were taken at distinct time intervals up to 6 min. And added sodium sulfite solution to stop any further oxidation immediately. All the kinetic experiments were performaed in the batch reactor at 25°C.

Results and Discussion To study the degradation kinetics of the EDCs by ferrate(VI) oxidation, several sets of tests were carried out at different pH values from pH 8.2 to pH 12, with the following initial reactant concentrations: [BPA]0=0.1 mM, [EE2]0=0.01 mM, [E1]0=0.01 mM, [E2]0=0.01 mM, [E3]0=0.01 mM and [Fe(VI)]0=0.05-0.5 mM. Ferrate(VI) in aqueous solution occurred in four forms that depended on pH as shown below:

Moreover, a kinetic model based on a second-order reaction was developed by considering that both the ferrate and the EDCs were dessociating compounds. In these studies, the ferrate was assumed to be mono-protonated (HFeO4-, pKa=7.23) and dissociated (FeO42-) form, and the EDCs were non-dissociated (EDC) and dissociated (EDC-) (11). Ferrate (VI) was a diprotic acid (H2FeO4=HFeO4-+H+, pka,H2FeO4=3.50 and HFeO4-=FeO42-+H+, pka,HFeO4-=7.23 (12, 13). The three phenolic EDCs were monoprotic acids (EE2, E2 and E3) or diprotic acid (BPA) for their phenolic moieties. Therefore, the oxidation reactions were summarized as follows (10):


The overall rate of EDC compound degradation was assumed to be the sum of the above two rates as follows:


According to the equilibrium of the two EDCs and ferrate species at different pH, the relationship between the concentrations of undissociated and dissociated EDCs and pH can be described by the following expressions:

Therefore,

Where [Fe(VI)]=[HFeO4-]+[FeO42-], [EDC]=[EDC]+[EDC-]. Dividing Eq. (8) by Eq. (9) and integrating the equation with the initial conditions (when t=0, [EDC]=[EDC]0 and [Fe(VI)]=[Fe(VI)]0), a pair of second-order equation for EDC degradation and ferrate(VI) reduction versus reaction time were expressed by Eq. (14) and (15), respectively.


Where


The rate constants k1, k1′ k2′, k11, k11′, k21 and k21′ were determined by the leasesqure method via the Matlab 6.5 program as shown in Figure 2.

Figure 2. Comparison between experimental data and kinetic model for the degradation of EDCs by ferrate(VI)

In addition, the reactions of ferrate(VI) and the phenolic EDCs are also described as first order by Eq.(12) (14)

Where kapp represented the apparent second-order rate constant for the reaction of ferrate(VI) with each EDC (EE2, E2, and BPA) as a function of pH, [Fe(VI)]tot represents the total concentration of ferrate(VI) species, and [EDC]tot represents the total concentration of each EDC species. The pH dependency of kapp for each phenolic EDC could be quantitatively modeled by Eq. (13)



Where [Fe(VI)]tot=[H2FeO4]+[HFeO4-]+[FeO42-], [EDC]tot=[EDC]+[EDC-]+ [EDC2-], αi and βj represented the respective species distribution coefficients for ferrate(VI) and phenolic EDC, i and j represented each of the three ferrate(VI) species and phenolic EDC species, respectively, and kij represented the species-specific second-order rate constant for the reaction between the ferrate(VI) species i with the phenolic EDC species j. The reactions of H2FeO4 and FeO42with the phenolic EDCs did not appear to contribute significantly to the overall reaction and thus were neglected in the model calculations (15). Therefore, the following reactions (Eq. 14-16) can be considered as main reactions between ferrate(VI) and the phenolic EDCs to explain the pH dependency of the reaction rates (14).

When considering the above reactions, the apparent second-order rate constant, kapp, was given by Eq. 17 or 18

Therefore, the following reactions (Eq. 19-21) can be considered as main reactions between Fe(VI) and the phenolic EDCs to explain the pH dependency of the reaction rates.



When considering the above reactions, the apparent second-order rate constant, kapp, was given by Eq. 22 or 23

Comparing the rate constants by Li and Lee was shown in Table 2 (10, 14) It was seen from Table 2 that the oxidizing power of mono-protonated ferrate, HFeO4-, was faster than non-protonated ferrate, FeO42-, for all of the EDCs, and that the dissociated (ionized) EDCs were more reactive, particularly with mono-pronated ferrate than with undissociated EDCs. It also refected the higher activating effect of the hydroxyl groups as a result of their deprotonation. For further investigation on the changing of substances in water, the UV scanning of the treated and untreated water samples were carried out during the oxidation process as presented in Figure 3.

Table 2. Summary of the rate constants for the reaction of Fe(VI) with selected EDCs No.

Compounds

k1(M-1s-1)a

k′1(M-1s-1)b

k2(M-1s-1)c

k2′(M-1s-1)d

1

EE2 (8)

3.05×102

8.52×102

9.1×102

5.11×105

EE2 (12)

-

9.4×102

5.4×105

-

E2 (8)

7.32×102

9.41×102

1.08×103

5.40×105

E2 (12)

-

1.0×103

5.4×105

-

BPA (8)

2.8×102

5.16×102

8.2×102

7.76×104

BPA (12)

-

8.2×102

8.0×104

2.6×105

4

E2 (8)

7.32×102

9.41×102

1.08×103

5.40×105

5

E3 (8)

9.28×102

1.0×103

1.12×103

5.44×105

2

3

a

FeO42-: undissociated EDC. b FeO42-: dissociated EDC. EDC. d HFeO4-: dissociated EDC.

c

HFeO4-: undissociated

As Figure 3(a) and Figure 3(b) showed, the absorbance of the untreated water was much lower than the water samples with ferrate(VI) treatment within the UV range of 210–600 nm. The absorbance of the treated samples expressed obvious differences within the UV range of 210-400 nm with the different ferrate(VI) doses. 344 Sharma et al.; Ferrites and Ferrates: Chemistry and Applications in Sustainable Energy and Environmental Remediation ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


Figure 3. UV scanning of the water oxidated by a range of ferrate doses (a) the graph of the actual data obtained from UV scanning, (b) the graph of differences between these treated samples and the untreated sample taken as the reference value

Conclusion In this paper, the reaction rate constants for BPA, EE2, E1, E2, and E3 oxidized by ferrate(VI) had been determined. The rate constants were determined by different kinetic models and the oxidation of the EDCs was found to be faster for mono-protonated ferrate, HFeO4-, than for non-protonated ferrate, FeO42-. It shows that higher activating effect of the hydroxyl groups as a result of their deprotonation. Among the five EDCs, the ferrate oxidation of the four steroid estrogens was faster (higher reaction rates) than that of BPA. These EDCs were more rapidly degraded than others because the unique structures of EDCs confer a relatively high degree of unsaturation and high electron density due to condensed benzene rings and aliphatic hydroxyl groups. In addition, some observations 345 Sharma et al.; Ferrites and Ferrates: Chemistry and Applications in Sustainable Energy and Environmental Remediation ACS Symposium Series; American Chemical Society: Washington, DC, 2016.

suggested that the π surface area and descriptors related to functional groups that were easily attacked by oxidants (16–18).

References 1.


2. 3.

4.

5.

6.

7.

8.

9.

10. 11. 12.

13.

14.

Lee, Y.; Cho, M.; Kim, J. Y.; Yoon, J. Chemistry of ferrate (Fe (VI)) in aqueous solution and its applications as a green chemical. J. Ind. Eng. Chem. 2004, 10, 161–171. Sharma, V. K. Potassium ferrate (VI): an environmentally friendly oxidant. Adv. Environ. Res. 2002, 6, 143–156. Lee, Y.; Um, I.-h.; Yoon, J. Arsenic (III) oxidation by iron (VI)(ferrate) and subsequent removal of arsenic (V) by iron (III) coagulation. Environ. Sci. Technol. 2003, 37, 5750–5756. Sharma, V. K.; Burnett, C. R.; Yngard, R. A.; Cabelli, D. E. Iron (VI) and iron (V) oxidation of copper (I) cyanide. Environ. Sci. Technol. 2005, 39, 3849–3854. Huang, H.; Sommerfeld, D.; Dunn, B. C.; Eyring, E. M.; Lloyd, C. R. Ferrate (VI) oxidation of aqueous phenol: kinetics and mechanism. J. Phys. Chem. A 2001, 105, 3536–3541. Rush, J.; Cyr, J.; Zhao, Z.; Bielski, B. The Oxidation of Phenol by Ferrate (VI) Andferrate (V). A Pulse Radiolysis and Stopped-Flow Study. Free Radical Res. 1995, 22, 349–360. Goff, H.; Murmann, R. K. Mechanism of isotopic oxygen exchange and reduction of ferrate (VI) ion (FeO42-). J. Am. Chem. Soc. 1971, 93, 6058–6065. Esperanza, M; Suidan, M T.; Fumitake, N.; Wang, Z. M.; Sorial, G. A. Determination of sex hormones and nonylphenol ethoxylates in the aqueous matrixes of two pilot-scale municipal wastewater treatment plants[J]. Environ. Sci. Technol. 2004, 38, 3028–3035. Sharma, V. K.; O’Connor, D. B.; Cabelli, D. E. Sequential one-electron reduction of Fe (V) to Fe (III) by cyanide in alkaline medium. J. Phys. Chem. B 2001, 105, 11529–11532. Li, C.; Li, X.; Graham, N. A study of the preparation and reactivity of potassium ferrate. Chemosphere 2005, 61, 537–543. Li, C.; Li, X.; Graham, N.; Gao, N. The aqueous degradation of bisphenol A and steroid estrogens by ferrate. Water Res. 2008, 42, 109–120. Licht, S.; Naschitz, V.; Halperin, L.; Halperin, N.; Lin, L.; Chen, J.; Ghosh, S.; Liu, B. Analysis of ferrate (VI) compounds and super-iron Fe (VI) battery cathodes: FTIR, ICP, titrimetric, XRD, UV/VIS, and electrochemical characterization. J. Power Sources 2001, 101, 167–176. Rush, J. D.; Zhao, Z.; Bielski, B. H. Reaction of ferrate (VI)/ferrate (V) with hydrogen peroxide and superoxide anion-A stopped-flow and premix pulse radiolysis study. Free Radical Res. 1996, 24, 187–198. Lee, Y.; Yoon, J.; von Gunten, U. Kinetics of the Oxidation of Phenols and Phenolic Endocrine Disruptors during Water Treatment with Ferrate (Fe(VI)). Environ. Sci. Technol. 2005, 39, 8978–8984. 346

Sharma et al.; Ferrites and Ferrates: Chemistry and Applications in Sustainable Energy and Environmental Remediation ACS Symposium Series; American Chemical Society: Washington, DC, 2016.


15. Sharma, V. K.; Burnett, C. R.; Millero, F. J. Dissociation constants of the monoprotic ferrate (VI) ion in NaCl media. Phys. Chem. Chem. Phys. 2001, 3, 2059–2062. 16. Lei, H. X.; Snyder, S. A. 3D QSPR models for the removal of trace organic contaminants by ozone and free chlorine. Water Res. 2007, 41, 4051–4060. 17. Fontela, M. H.; Galceran, M. T.; Ventura, F. Occurrence and removal of pharmaceuticals and hormones through drinking water treatment. Water Res. 2011, 45, 1432–1442. 18. Schilir, Ò T.; Pignata, C.; Rovere, R.; Fea, E.; Gilli, G. The endocrine disrupting activity of surface waters and of wastewater treatment plant effluents in relation to chlorination. Chemosphere 2009, 75, 335–340.


The Degradation Kinetics of Typical EDCs (Endocrine Disruption

Recommend Documents