Kinetic correlation between degradation and dechlorination of perchloroethylene in the Fenton reaction

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1 Koren J. Chem. Eng., 27(6), (2010) DOI: /s INVITED REVIEW PAPER Kinetic correltion etween degrdtion nd dechlorintion of perchloroethylene in the Fenton rection Hee-Sik Kim*, Wn-Suk Lee*, Chi-Yong Ahn*, Byung-Hyuk Kim*, Jng-Eok Kim**, nd Hee-Mock Oh*, *Environmentl Biotechnology Reserch Center, KRIBB, Dejeon , Kore **Deprtment of Agriculturl Chemistry, Kyungpook Ntionl University, Degu , Kore (Received 8 Ferury 2010 ccepted 1 April 2010) Astrct In the Fenton rection, degrdtion nd dechlorintion re directly ffected y the concentrtions of hydrogen peroxide nd Fe 3+. Although there is considerle reserch on the iodegrdtion of chlorinted compounds comined with the Fenton rection, the kinetics of degrdtion nd dechlorintion of the rection, with vrious concentrtions of hydrogen peroxide nd Fe 3+, hve een rrely investigted. Therefore, we investigted the degrdtion nd dechlorintion of PCE with vrious concentrtions of hydrogen peroxide nd Fe 3+. The initil concentrtion of PCE (10 µm) decresed from vlue of 8.9 µm (with 0.1 mm of hydrogen peroxide nd 5 mm of Fe 3+ ) to 1.1 µm (with 10 mm of hydrogen peroxide nd 5 mm of Fe 3+ ); the respective vlues for chloride ions produced were 0.9 nd 21.6 µm. Also, the initil 10 µm of PCE decresed from 8.9 (with 0.1 mm of Fe 3+ nd 5 mm of hydrogen peroxide) to 2.2 µm (with 10 mm of Fe 3+ nd 5 mm of hydrogen peroxide); the respective chloride ions produced were 0.7 nd 14.5 µm. The logrithmic correltions etween the degrdtion nd dechlorintion coefficients were nd for concentrtions of hydrogen peroxide nd Fe 3+, respectively. Both coefficients were used, from ll possile cses, to derive six models which displyed oth the rtio of degrdtion nd dechlorintion nd the hydrogen peroxide nd Fe 3+ concentrtions. The dechlorintion of PCE could then e predicted with the model otined y the coefficient with the concentrtion of hydrogen peroxide nd Fe 3+. The models could e pplied to vrious Fenton rections for optimiztion of degrdtion or dechlorintion, such s iodegrdtion of PCE which is scrcely degrded y eroic cteri. Key words: Dechlorintion Vlue, Degrdtion, Fenton Rection, Kinetic Correltion, Perchloroethylene (PCE) INTRODUCTION Perchloroethylene (PCE) is widely used chlorinted solvent nd common contminnt in groundwter. Aquifers contining PCEcontminted wter my e used s source for municipl wter supplies [1]. PCE is lso suspected crcinogen; therefore, the fte of PCE in the environment hs ecome fundmentl helth concern [2]. Since the Fenton rection is well-known potent oxidtive rection, mny reserchers hve investigted the ppliction of the Fenton rection for degrdtion of vrious orgnic compounds [3-6]. For the tretment of these reclcitrnt compounds, numer of chemicl processes hve een investigted, including oxidtion y Fenton s regent. The dvntge of Fenton s rection, compound degrdtion y Fenton s regent, my yield (i) prtil minerliztion [7], (ii) lowered toxicity [8], nd (iii) incresed susceptiility to iodegrdtion [9]. Fenton s regent ( mixture of hydrogen peroxide nd ferrous slt) hs gined gret mount of ttention, due to its strong oxidtion cpilities nd low environmentl impcts [10]. A Fenton system requiring queous Fe(II) for the formtion of OH hs een properly operted t the ph rnge of 2-4 y voiding the formtion of Fe(OH) 3(s) [11,12]. Severl studies hve lso reported tht PCE ws dechlorinted y Fenton rection [13,14]. Individul kinetic models nd rection pthwys of the Fenton rection hve lso een proposed y To whom correspondence should e ddressed. E-mil: heemock@kri.re.kr 1750 mny [15-18]. PCE, which hs four chloride ions, is not esily degrded y eroic cteri [2]. For iodegrdtion of PCE in wstewter, PCE hs to e trnsformed to more esily iodegrdle form y other tretments. Vrious chemicl methods, which could e used in conjunction with iologicl methods, hve een studied to degrde PCE [19]. Among these methods, the Fenton rection ws one of the most frequently used for the dechlorintion of PCE, ecuse this rection converts reclcitrnt toxic compounds into iodegrdle nd less toxic [8,9]. In the Fenton rection, degrdtion nd dechlorintion re directly ffected y the concentrtions of hydrogen peroxide nd Fe 3+. Therefore, the solute nd reltive concentrtions of hydrogen peroxide nd Fe 3+ re very importnt in the overll process, including the Fenton rection. Although there is considerle reserch on the iodegrdtion of chlorinted compounds comined with the Fenton rection, the kinetics of degrdtion nd dechlorintion of the rection, with vrious concentrtions of hydrogen peroxide nd Fe 3+, hve een rrely investigted. In this study, we investigted the conditions of the degrdtion nd dechlorintion of PCE. Kinetic experiments were conducted to investigte the effect of vrious concentrtions of hydrogen peroxide nd Fe 3+ on the degrdtion nd dechlorintion of PCE nd to drw the optiml opertion conditions. We nlyzed the coefficients of degrdtion nd dechlorintion, nd expressed the correltions with the slopes, which were the coefficients in the first-order degree with degrdtion nd dechlorintion. Finlly, we ttempted to clssify ll possile exmples into series of models to show not only the most importnt fctors ffecting dechlorintion, ut lso the opti-

2 PCE degrdtion nd dechlorintion in Fenton rection 1751 ml concentrtions of hydrogen peroxide nd Fe 3+. EXPERIMENTAL 1. Chemicls PCE nd Fe(NO 3 ) 3 9H 2 O were purchsed from Sigm (Milwukee, USA). Hydrogen peroxide ws purchsed from Wko (Tokyo, Jpn). 2. Degrdtion of PCE In the Fenton rection, deionized wter (5 ml) contining Fe(NO 3 ) 3 9H 2 O nd PCE ws dispensed into 60-ml hedspce vils. PCE ws dded with syringe, s n queous stock solution, through the septum of ech vil, resulting in finl concentrtion of 10 µm (=1.66 mg/l), which is similr to the PCE concentrtions detected in the contminted sites in Switzerlnd nd the USA [20]. The concentrtions of hydrogen peroxide nd iron were modified, sed on the previous study [19]. Hydrogen peroxide ws dded to the vils to initite the Fenton rection. ph ws djusted to 5.0, nd the vils were incuted in shker (120 rpm) for 90 min t 30 o C. PCE degrdtion ws quntittively investigted, sed on the reduction of PCE, using gs chromtogrph (Vrin 3400 CX, Wlnut Creek, CA, USA). The smples (2 µl) were injected with 25-µl gs-tight syringe into gs chromtogrph equipped with flme ioniztion detector nd Supelco SPB-5 (Supelco Drk, Bellefonte, PA, USA) on 30 m 250 µm cpillry column (column temperture: 70 o C; injector temperture: 150 o C; detector temperture: 250 o C; 30 ml/min; N 2 s the crrier gs). 3. Dechlorintion of PCE The dechlorintion of PCE ws investigted during the Fenton rection from the concentrtion of chloride ion, which ws nlyzed y ion chromtogrphy (IC). The IC system (Wters, Milford, MA, USA) consisted of pump (HP 526; Wters), column heter (HP 530; Wters), nd conductivity detector (HP 550; Wters). The recently developed utosuppressor (Eris 1000HP; Alltech, Nicholsville, KY, USA) ws used in suppressor nlyses. The nlyticl columns for nion seprtion were Ion Pc AG 14 nd AS 14 (Dionex, Sn Frncisco, CA, USA). RESULTS AND DISCUSSION 1. Degrdtion nd Dechlorintion of PCE y the Fenton Rection The degrdtion of PCE y the Fenton rection ws investigted t vrious concentrtions of hydrogen peroxide. The initil concentrtion (10 µm) of PCE decresed to 8.9, 7.45, 7.0, 4.8 nd 1.1 µm with 0.1, 0.5, 1.0, 5 nd 10 mm of hydrogen peroxide nd 5 mm of Fe 3+ fter 90 min, respectively (Fig. 1()). The concentrtion of chloride ions, which were produced from PCE y the Fenton rection, incresed to 0.9, 3.1, 7.6, 15.2 nd 21.6 µm fter 90 min, with the sme concentrtions of hydrogen peroxide nd Fe 3+, respectively (Fig. 1()). Furthermore, the initil concentrtion of PCE decresed Fig. 1. Effects of vrious concentrtions of hydrogen peroxide nd Fe 3+ on the degrdtion nd dechlorintion of PCE in the Fenton rection. Hydrogen peroxide ws dded t concentrtion of 0.1, 0.5, 1.0, 5.0 nd 10 mm to Fenton regent contining 5 mm of Fe 3+ ((), ()). In similr mnner, Fe 3+ ws dded to Fenton regent contining 5 mm of hydrogen peroxide ((c), (d)). Koren J. Chem. Eng.(Vol. 27, No. 6)

3 1752 H.-S. Kim et l. to 8.9, 8.2, 7.3, 3.4 nd 2.2 µm with 0.1, 0.5, 1.0, 5 nd 10 mm of Fe 3+ nd 5 mm of hydrogen peroxide, respectively (Fig. 1(c)). The concentrtion of chloride ions incresed to 0.7, 1.5, 3.0, 11.4 nd 14.5 µm, respectively (Fig. 1(d)). These results show tht the concentrtion of PCE decresed with the incresing hydrogen peroxide nd Fe 3+ concentrtions. It seemed tht the concentrtions of hydrogen peroxide nd Fe 3+ re importnt fctors which could determine the efficiency of the Fenton rection. According to Leung et l. [16], n increse of hydrogen peroxide nd Fe 3+ could increse the degrdtion of PCE in the Fenton rection. The Fenton rection is cused y n hydroxyl rdicl from hydrogen peroxide nd Fe 3+. Therefore, the fct tht PCE decresed with incresing hydrogen peroxide nd Fe 3+ ws due to n incresed concentrtion of hydroxyl rdicl. While PCE is degrded y the Fenton rection, chloride ions re produced from PCE. When 8.9 µm of PCE ws degrded y 10 mm of hydrogen peroxide nd 5 mm of Fe 3+, 21.6 µm of chloride ion ws produced. While 14.5 µm of chloride ion ws relesed from 7.8 µm of PCE y 10 mm of hydrogen peroxide nd 5 mm of Fe 3+. Therefore, the concentrtion of chloride ion incresed with incresing hydrogen peroxide nd Fe 3+. It seems tht the numer of hydroxyl rdicls yielded y high concentrtions of hydrogen peroxide is lrger thn the numer yielded y high concentrtion of Fe 3+. Mny reserchers hve reported tht the Fenton rection yielded hydroxyl rdicls which were le to oxidize vrious orgnic compounds [10, 14,21-24]. The dechlorintion vlue (D m ), clculted from Cl mol/dpce Tle 1. Effects of hydrogen peroxide nd Fe 3+ concentrtions on dechlorintion of PCE Concentrtion (mm) Dechlorintion vlue (D m ) H 2 O 2 Fe 3+c Bsed on DCl mol/dpce mol Rected with 5 mm of Fe 3+ c Rected with 5 mm of hydrogen peroxide mol, elucidted the dechlorintion of PCE. When PCE ws degrded y 10 mm of hydrogen peroxide nd 10 mm of Fe 3+, the vlues were 2.5 nd 1.9, respectively (Tle 1). In other words, out 2.5 chloride ions per one molecule of PCE were relesed y 10 mm of hydrogen peroxide nd 5 mm of Fe 3+ ; 1.9 chloride ions per one molecule of PCE were relesed y 10 mm of hydrogen peroxide nd 5mM of Fe 3+. Therefore, hydrogen peroxide ws more effective for dechlorintion in the Fenton rection. Dec nd Bollg [25] predicted the dechlorintion of chlorinted phenols nd nilines in coupling rections with the dechlorintion numer (DN), which ws clculted from DPCE mol per one Cl mol. DN is useful in finding the rection position, ut is not suitle for PCE since ll sustitu- Fig. 2. Reltionship etween degrdtion coefficient (k PCE ) nd concentrtion of hydrogen peroxide () nd Fe 3+ (c). Reltionship etween dechlorintion coefficient (k Cl ) nd concentrtion of hydrogen peroxide () nd Fe 3+ (d). Novemer, 2010

4 PCE degrdtion nd dechlorintion in Fenton rection 1753 tion positions of PCE re occupied with chlorines in ethene. Therefore, we otin D m to otin the theoreticl numer of chlorine ions relesed from one molecule of PCE. 2. Correltion etween k PCE nd k Cl The reltionship etween degrdtion coefficient (k PCE ) nd concentrtion of hydrogen peroxide nd Fe 3+ ws investigted. Fig. 2 shows tht the non-liner coefficient for the concentrtion of hydrogen peroxide ws The k PCE[H2O2] incresed with incresing hydrogen peroxide. The non-liner coefficient for the concentrtion of Fe 3+ (k PCE[Fe] ) ws The k PCE[Fe] lso incresed with incresing Fe 3+. The reltionship etween dechlorintion coefficient (k Cl ) on the concentrtions of concentrtion of hydrogen peroxide nd Fe 3+ ws investigted. Fig. 2() shows tht the non-liner coefficient for the concentrtion of hydrogen peroxide ws The k Cl[H2O2] incresed logrithmiclly with incresing hydrogen peroxide. The nonliner coefficient for the concentrtion of Fe 3+ (k Cl[Fe] ) ws The k Cl[Fe] lso incresed with incresing Fe 3+. Weeks et l. [26] found tht the first-order model provided the est fit for chnge of concentrtions of H 2 O 2 nd TCE s function of time in their experimentl studies. They lso noted tht the ctul processes involved in the degrdtion of H 2 O 2 nd TCE re more complex thn first-order model predictions. Degrdtion rte constnts of TCE otined in the tch experiments depended on the experimentl conditions, such s the initil [H 2 O 2 ]/[Fe 2+ ] rtio nd the initil H 2 O 2 nd Fe 2+ concentrtions. Rections in the lter stges my hve een ctlyzed y regenerted Fe 2+ nd possily Fe 3+. The coefficients (slope) in the liner equtions were trnsformed y nturl log trnsformtion from the degrdtion nd dechlorintion rte constnts. The logrithmic equtions, otined y liner regression, etween degrdtion nd concentrtions of hydrogen peroxide nd Fe 3+ were expressed s: ln k PCE[Fe] = F + F ln C Fe (1) ln k PCE[H2O2] = H + H ln C H2O2 (2) The equtions etween dechlorintion nd concentrtions of hydrogen peroxide nd Fe 3+ were expressed s: ln k Cl[Fe] =m F +n F ln C Fe (3) ln k Cl[H2O2] =m H +n H ln C H2O2 (4) Eqs. (1)-(4) were otined y logrithmic trnsform of results in Fig. 2. Sustituting Eq. (1) in Eq. (3), we otin: ln k PCE[Fe] = F + F (ln k Cl[Fe] -m F )/n F =q F +p F ln k Cl[Fe] (5) And sustituting Eq. (2) in Eq. (4), we otin: ln k PCE[H2O2] = H + H (ln k Cl[H2O2] -m H )/n H =q H +p H ln k Cl[H2O2] (6) According to Eqs. (5) nd (6), the first-order equtions versus k Cl must constitute stright line. In the equtions, k PCE is expressed y constnts, coefficients nd k Cl. The coefficients, p F nd p H, provide gret del of informtion. (i) If p F nd p H re higher thn 1, k PCE will chnge more effectively rther thn k Cl (Fig. 3()). In other words, the mol numer for PCE degrdtion ws lrger thn tht for dechlorintion. Therefore, the degrdtion of PCE could occur in the Fenton rection without dechlorintion. (ii) If p F nd p H re lower thn 1, k Cl would chnge more effectively rther thn k PCE Fig. 3. Slopes for six possile models in the kinetic correltion etween degrdtion nd dechlorintion. p H nd p F re coefficients of the equtions which expressed degrdtion nd dechlorintion with vrious concentrtions of hydrogen peroxide nd Fe 3+. (Fig. 3()). In other words, the degrdtion rte is lower thn the dechlorintion rte. Therefore, over one chloride ion ws relesed during degrdtion of one molecule of PCE. (iii) If p F nd p H re equl to 1, k Cl is directly proportionl to k PCE (Fig. 3(c)). This mens tht one chloride ion is relesed during degrdtion of one molecule of PCE. (iv) If p F is higher thn p H, the concentrtion of hydrogen peroxide will hve more effect on dechlorintion thn Fe 3+ (Fig. 3(d)). (v) If p H is higher thn p H, the concentrtion of Fe 3+ will hve more effect on dechlorintion thn the hydrogen peroxide (Fig. 3(e)). (vi) If p H is equl to p F, the effect of hydrogen peroxide on dechlorintion will e the sme s Fe 3+ (Fig. 3(f)). Sustituting vlues for the constnts nd coefficients in the equtions, we otin: ln k PCE[Fe] = ln k Cl[Fe] (7) ln k PCE[H2O2] = ln k Cl[H2O2] (8) Tle 2 shows the slopes of the logrithmic equtions. The slopes of Eqs. (1) nd (2), which expressed ln k PCE for the concentrtion of Fe 3+ nd hydrogen peroxide, were nd , respectively, while the slopes Eqs. (3) nd (4), which expressed ln k Cl for the concentrtion of Fe 3+ nd hydrogen peroxide, were nd , respectively. The slopes (p F nd p H ) of Eqs. (5) nd (6) were Tle 2. Coefficients of dechlorintion nd degrdtion with concentrtions of hydrogen peroxide nd Fe 3+ in the logrithmic eqution Coefficients Slope k PCE[H2O2] k PCE[Fe] k Cl[H2O2] k Cl[Fe] k Cl[H2O2] on k PCE[H2O2] k Cl[Fe] on k PCE[Fe] Coefficient (p H ) of the next eqution, ln k PCE[H2O2] =q H +p H ln k Cl[H2O2] Coefficient (p F ) of the next eqution, ln k PCE[Fe] =q F +p F ln k Cl[Fe] Koren J. Chem. Eng.(Vol. 27, No. 6)

5 1754 H.-S. Kim et l nd , respectively. Fig. 3 shows the models of degrdtion nd dechlorintion occurring in the Fenton rection with vrious concentrtions of hydrogen peroxide nd Fe 3+. Since oth liner regression coefficients (slope) were lower thn 1 in Fig. 3(), the dechlorintion rection occurred more often thn the degrdtion rection. In other words, over one chloride ion ws produced y the Fenton rection during the degrdtion of one molecule of PCE. Since p F ws higher thn p H in Fig. 3(d), the concentrtion of hydrogen peroxide ws more effective in dechlorintion of PCE thn Fe 3+. De Lt nd Gllrd [22] reported tht the production rte of hydroxyl rdicls incresed with the rtio of hydrogen peroxide to Fe 3+ (H 2 O 2 /Fe 3+ ). They could not explin how the hydrogen peroxide/ Fe 3+ rtio ffected degrdtion nd dechlorintion. In our experiments, however, the models show tht the hydrogen peroxide/fe 3+ rtio could ffect degrdtion nd dechlorintion. CONCLUSIONS In the equtions, when oth coefficients, expressed y degrdtion nd dechlorintion rte constnts, were elow 1 nd the Fe 3+ coefficient ws greter thn tht of hydrogen peroxide, the dechlorintion coefficient ws higher thn the degrdtion coefficient of PCE, nd hydrogen peroxide ws more effective dechlorintion fctor thn Fe 3+ in the Fenton rection. We formulted six possile models for the correltion etween degrdtion/dechlorintion nd vrious fctors in the Fenton rection. The dechlorintion of PCE could then e predicted with the model otined y the coefficient with the concentrtion of hydrogen peroxide nd Fe 3+. In the Fenton rection, dechlorintion of PCE could e regulted y the model coefficients. In ddition, the optimum concentrtion of hydrogen peroxide nd Fe 3+ could e otined from the models. Therefore, the models could e pplied to vrious Fenton rections for optimiztion of degrdtion or dechlorintion, such s iodegrdtion of PCE which is scrcely degrded y eroic cteri. ACKNOWLEDGEMENTS This study ws supported y the KRIBB Reserch Inititive Progrm nd the Environmentl Biotechnology Ntionl Core Reserch Center. DN k Cl k PCE NOMENCLATURE : dechlorintion numer : dechlorintion coefficient : PCE degrdtion coefficient REFERENCES 1. Y. C. Chng, M. Htsu, K. Jung, Y. S. Yoo nd K. Tkmizw, J. Biosci. Bioeng., 89, 489 (2000). 2. D. Ryoo, H. Shim, K. Cnd, P. Brieri nd T. K. Wood, Nt. Biotechnol., 18, 775 (2000). 3. Y. O. Kim, H. U. Nm, Y. R. Prk, J. H. Lee, T. J. Prk nd T. H. Lee, Koren J. Chem. Eng., 21, 801 (2004). 4. A. M. Mckinzi nd T. J. Dichristin, Environ. Sci. Technol., 33, 1886 (1999). 5. C. Wlling nd S. Kto, J. Am. Chem. Soc., 93, 4275 (1971). 6. Q. Wng nd A. T. Lemley, Environ. Sci. Technol., 35, 4509 (2001). 7. Z. M. Li, S. D. Comfort nd P. J. She, J. Environ. Qul., 26, 480 (1997). 8. D. A. Brton nd E. P. Drke, Wter Sci. Technol., 29, 229 (1994). 9. J. B. Crerry nd T. M. Benzing, Wter Sci. Technol., 23, 367 (1991). 10. G. Chen, G. E. Hog, P. Chedd, F. Ndim, B. A. Woody nd G. M. Dos, J. Hzrd. Mter., B87, 171 (2001). 11. Y. Lee nd W. Lee, J. Hzrd. Mter., Doi: /j.jhzmt (2010). 12. J. J. Pigntello, E. Oliveros nd A. McKy, Crit. Rev. Environ. Sci. Technol., 36, 1 (2006). 13. J. Howsweng, R. J. Wtts, D. L. Wshinton, A. L. Teel, T. F. Hess nd R. L. Crwford, Environ. Sci. Technol., 35, 2961 (2001). 14. J. J. Pigntello, D. Liu nd P. Huston, Environ. Sci. Technol., 33, 1832 (1999). 15. J. De Lt, H. Gllrd, S. W. Ancelin nd B. Legue, Chemosphere, 39, 2693 (1999). 16. S. W. Leung, R. J. Wtts nd G. C. Miller, J. Environ. Qul., 21, 377 (1992). 17. J. J. Pigntello, Environ. Sci. Technol., 26, 944 (1992). 18. M. I. Stefn, A. R. Hoy nd J. R. Bolton, Environ. Sci. Technol., 30, 2382 (1996). 19. F. Büyüksönmez, T. F. Hess, R. L. Crwford, A. Pszczynski nd R. J. Wtts, Appl. Environ. Microiol., 65, 2784 (1999). 20. J. De Zune, Hndook of drinking wter qulity, Edited y Vn Nostrnd Reinhold, New York (1997). 21. J. Beltrn de Heredi, J. Torregros, J. R. Dominguez nd J. A. Peres, Chemosphere, 45, 85 (2001). 22. J. De Lt nd H. Gllrd, Environ. Sci. Technol., 33, 2726 (1999). 23. M. A. Oturn, N. Oturn, C. Lhitte nd S. Trevin, J. Electronl Chem., 507, 96 (2001). 24. M. L. Rodriguez, V. I. Timokhin, S. Contres, E. Chmrro nd S. Esplugs, Adv. Environ. Res., 7, 583 (2003). 25. J. Dec nd J. M. Bollg, Environ. Sci. Technol., 29, 657 (1995). 26. K. R. Weeks, C. J. Bruell nd N. R. Mohnty, J. Soil Sediment Contmintion, 9, 331 (2000). Novemer, 2010