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Shin, Jaedon,von Gunten, Urs,Reckhow, David A.,Allard, Sebastien,Lee, Yunho American Chemical Society 2018 Environmental science & technology Vol.52 No.13
<P>Oxidative treatment of iodide-containing waters can form toxic iodinated disinfection byproducts (I-DBPs). To better understand the fate of iodine, kinetics, products, and stoichiometries for the reactions of ferrate(VI) with iodide (I<SUP>-</SUP>) and hypoiodous acid (HOI) were determined. Ferrate(VI) showed considerable reactivities to both I<SUP>-</SUP> and HOI with higher reactivities at lower pH. Interestingly, the reaction of ferrate(VI) with HOI (<I>k</I> = 6.0 × 10<SUP>3</SUP> M<SUP>-1</SUP> s<SUP>-1</SUP> at pH 9) was much faster than with I<SUP>-</SUP> (<I>k</I> = 5.6 × 10<SUP>2</SUP> M<SUP>-1</SUP> s<SUP>-1</SUP> at pH 9). The main reaction pathway during treatment of I<SUP>-</SUP>-containing waters was the oxidation of I<SUP>-</SUP> to HOI and its further oxidation to IO<SUB>3</SUB><SUP>-</SUP> by ferrate(VI). However, for pH > 9, the HOI disproportionation catalyzed by ferrate(VI) became an additional transformation pathway forming I<SUP>-</SUP> and IO<SUB>3</SUB><SUP>-</SUP>. The reduction of HOI by hydrogen peroxide, the latter being produced from ferrate(VI) decomposition, also contributes to the I<SUP>-</SUP> regeneration in the pH range 9-11. A kinetic model was developed that could well simulate the fate of iodine in the ferrate(VI)-I<SUP>-</SUP> system. Overall, due to a rapid oxidation of I<SUP>-</SUP> to IO<SUB>3</SUB><SUP>-</SUP> with short-lifetimes of HOI, ferrate(VI) oxidation appears to be a promising option for I-DBP mitigation during treatment of I<SUP>-</SUP>-containing waters.</P> [FIG OMISSION]</BR>
Reaction of Ferrate(VI) with ABTS and Self-Decay of Ferrate(VI): Kinetics and Mechanisms
Lee, Yunho,Kissner, Reinhard,von Gunten, Urs American Chemical Society 2014 Environmental science & technology Vol.48 No.9
<P>Reactions of ferrate(VI) during water treatment generate perferryl(V) or ferryl(IV) as primary intermediates. To better understand the fate of perferryl(V) or ferryl(IV) during ferrate(VI) oxidation, this study investigates the kinetics, products, and mechanisms for the reaction of ferrate(VI) with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and self-decay of ferrate(VI) in phosphate-buffered solutions. The oxidation of ABTS by ferrate(VI) via a one-electron transfer process produces ABTS<SUP>•+</SUP> and perferryl(V) (<I>k</I> = 1.2 × 10<SUP>6</SUP> M<SUP>–1</SUP> s<SUP>–1</SUP> at pH 7). The perferryl(V) mainly self-decays into H<SUB>2</SUB>O<SUB>2</SUB> and Fe(III) in acidic solution while with increasing pH the reaction of perferryl(V) with H<SUB>2</SUB>O<SUB>2</SUB> can compete with the perferryl(V) self-decay and produces Fe(III) and O<SUB>2</SUB> as final products. The ferrate(VI) self-decay generates ferryl(IV) and H<SUB>2</SUB>O<SUB>2</SUB> via a two-electron transfer with the initial step being rate-limiting (<I>k</I> = 26 M<SUP>–1</SUP> s<SUP>–1</SUP> at pH 7). Ferryl(IV) reacts with H<SUB>2</SUB>O<SUB>2</SUB> generating Fe(II) and O<SUB>2</SUB> and Fe(II) is oxidized by ferrate(VI) producing Fe(III) and perferryl(V) (<I>k</I> = ∼10<SUP>7</SUP> M<SUP>–1</SUP> s<SUP>–1</SUP>). Due to these facile transformations of reactive ferrate(VI), perferryl(V), and ferryl(IV) to the much less reactive Fe(III), H<SUB>2</SUB>O<SUB>2</SUB>, or O<SUB>2</SUB>, the observed oxidation capacity of ferrate(VI) is typically much lower than expected from theoretical considerations (i.e., three or four electron equivalents per ferrate(VI)). This should be considered for optimizing water treatment processes using ferrate(VI).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-9/es500804g/production/images/medium/es-2014-00804g_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es500804g'>ACS Electronic Supporting Info</A></P>
Lee, Yunho,Yoon, Jeyong,Gunten, Urs von 한국공업화학회 2005 응용화학 Vol.9 No.1
The kinetics of oxidation of phenolic water contaminants by ferrate (Fe(Ⅵ)) were investigated, especially focusing on phenolic endocrine disrupting chemicals (EDCs), such as, ethinylestradiol (EE2), estradiol (E2), and bisphenol-A (BPA). The second-order rate constants of Fe(Ⅵ) (k_(app)) with selected EDCs and many substituted phenols were determined in the pH range 611. The k_(app) of selected EDCs at pH 7 were above 600 M^(-1) sec^(-1), indicating that these EDCs can be completely transformed during water treatment with Fe (Ⅵ) . From the pH-dependency of kapp, each elementary reaction rate constant, i.e., the reaction of HFeO₄^(-) with neutral phenols (k_(HFeO4-/PhOH)) and the reaction of HFeO₄^(-) with ionized phenols (k_(HFe04-/PhO-)) was calculated. Correlation analysis based on a constants and pK_(a) values of substituted phenols revealed significant quantitative structure-activity relationships for both k_(HFe04-/PhOH) and k_(HFeO4-/PhO-). Experiments performed with lake water and wastewater showed that the rate constants determined in pure water could be applied to predict the oxidation of selected EDCs in real waters. From the comparison of reactivity toward phenolic EDCs, Fe(Ⅵ) was found to be less reactive than ozone and chlorine dioxide, but more reactive than chlorine. Overall, the results indicate that Fe(Ⅵ) is effective to treat waters containing phenolic contaminants.
Lee, Yunho,Imminger, Stefanie,Czekalski, Nadine,von Gunten, Urs,Hammes, Frederik Elsevier 2016 Water research Vol.101 No.-
<P><B>Abstract</B></P> <P>Inactivation kinetics of autochthonous bacteria during ozonation of wastewater effluents were investigated using cultivation-independent flow cytometry (FCM) with total cell count (TCC) and intact cell count (ICC) and intracellular adenosine triphosphate (ATP) analysis. The principles of the methods including ozone inactivation kinetics were demonstrated with laboratory-cultured <I>Escherichia coli</I> spiked into filtered and sterilized wastewater effluent. Both intracellular ATP and ICC decreased with increasing ozone doses, with ICC being the more conservative parameter. The log-inactivation levels (−log(N/N<SUB>0</SUB>) of <I>E. coli</I> reached the method detection limits for FCM (∼3) and ATP (∼1.7) at specific ozone doses of ≥0.5 gO<SUB>3</SUB>/gDOC. During ozonation of four real wastewater effluents, the log-inactivation of autochthonous bacteria with FCM ICC was 0.3–1.0 for 0.25 gO<SUB>3</SUB>/gDOC and increased to 1.1–2.1 for 0.5 gO<SUB>3</SUB>/gDOC, but remained at a similar level of 1.5–2.8 for a further increase of the specific ozone doses to 1.0 and 1.5 gO<SUB>3</SUB>/gDOC. The FCM data also showed that autochthonous bacteria were composed of communities with high and low ozone reactivity. The inactivation levels measured with intracellular ATP were reasonably correlated to ICC (r<SUP>2</SUP> = 0.8). Overall, FCM and ATP measurements were demonstrated to be useful tools to monitor the inactivation of autochthonous bacteria during ozonation of municipal wastewater effluents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ozone inactivation kinetics of wastewater effluent studied by FCM, ATP and cultivation. </LI> <LI> For <I>E. coli</I>, inactivation was in order of cultivation, ATP, and FCM-ICC. </LI> <LI> FCM and ATP were useful for measuring inactivation of autochthonous wastewater bacteria. </LI> <LI> 0.5 gO<SUB>3</SUB>/gDOC resulted in over 99% decrease of cell viability by FCM and ATP analysis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Yunho,Gerrity, Daniel,Lee, Minju,Bogeat, Angel Encinas,Salhi, Elisabeth,Gamage, Sujanie,Trenholm, Rebecca A.,Wert, Eric C.,Snyder, Shane A.,von Gunten, Urs American Chemical Society 2013 Environmental science & technology Vol.47 No.11
<P>Ozonation is effective in improving the quality of municipal wastewater effluents by eliminating organic micropollutants. Nevertheless, ozone process design is still limited by (i) the large number of structurally diverse micropollutants and (ii) the varying quality of wastewater matrices (especially dissolved organic matter). These issues were addressed by grouping 16 micropollutants according to their ozone and hydroxyl radical (<SUP>•</SUP>OH) rate constants and normalizing the applied ozone dose to the dissolved organic carbon concentration (i.e., g O<SUB>3</SUB>/g DOC). Consistent elimination of micropollutants was observed in 10 secondary municipal wastewater effluents spiked with 16 micropollutants (∼2 μg/L) in the absence of ozone demand exerted by nitrite. The elimination of ozone-refractory micropollutants was well predicted by measuring the <SUP>•</SUP>OH exposure by the decrease of the probe compound <I>p</I>-chlorobenzoic acid. The average molar <SUP>•</SUP>OH yields (moles of <SUP>•</SUP>OH produced per mole of ozone consumed) were 21 ± 3% for g O<SUB>3</SUB>/g DOC = 1.0, and the average rate constant for the reaction of <SUP>•</SUP>OH with effluent organic matter was (2.1 ± 0.6) × 10<SUP>4</SUP> (mg C/L)<SUP>−1</SUP> s<SUP>–1</SUP>. On the basis of these results, a DOC-normalized ozone dose, together with the rate constants for the reaction of the selected micropollutants with ozone and <SUP>•</SUP>OH, and the measurement of the <SUP>•</SUP>OH exposure are proposed as key parameters for the prediction of the elimination efficiency of micropollutants during ozonation of municipal wastewater effluents with varying water quality.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2013/esthag.2013.47.issue-11/es400781r/production/images/medium/es-2013-00781r_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es400781r'>ACS Electronic Supporting Info</A></P>