Article

Chlorination of Iodide-Containing Waters in the Presence of CuO: Formation of Periodate

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Abstract

It has been shown previously that the disproportionation of halogen-containing oxidants (e.g., HOCl, HOBr and ClO2) is enhanced by a CuO-catalyzed process. In this study, the transformation of iodine during chlorination in the presence of CuO was investigated. There is no significant enhancement of the disproportionation of hypoiodous acid (HOI) in the presence of CuO. The formation rate of iodate in the CuO-HOCl-I- system significantly increased when compared to homogeneous solutions, which was ascribed to the activation of HOCl by CuO enhancing its reactivity towards HOI. In this reaction system, iodate formation rates increase with increasing CuO (0-0.5 g L-1) and bromide (0-2 μM) doses and with decreasing pH (9.6-6.6). Iodate does not adsorb to the CuO surfaces used in this study. Nevertheless, iodate concentrations decreased after a maximum was reached in the CuO-HOCl-I--(Br-) systems. Similarly, the iodate concentrations decrease as a function of time in the CuO-HOCl-IO3- or CuO-HOBr-IO3- system, and the rates increase with decreasing pH (6.6-9.6) due to the enhanced reactivity of HOCl or HOBr in presence of CuO. It could be demonstrated that iodate is oxidized to periodate by a CuO-activated hypohalous acid, which is adsorbed on the CuO surface. No periodate could be measured in solution because it was mainly adsorbed to CuO. The adsorbed periodate was identified by scanning electron microscopy plus energy dispersive spectroscopy and X-ray photoelectron spectroscopy.

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... Three forms of iodine are usually present in natural waters, iodide (I À ), iodate (IO À 3 ), and organic-iodine (Liu et al., 2014). The main species are I À and IO À 3 in fresh water and seawater, respectively. ...
... The oxidation of I À by ClO 2 occurred through an initial step of the formation of I $ , similar to Fe(VI). Other oxidants (ozone, chlorine, and chloramine) also reacted fast with I À and the product was HOI (HOI # H þ þ OI À ; pK a ¼ 10.4 (Liu et al., 2014). Under the conditions of treatment, HOI may go through different processes: (i) disproportionate to IO À 3 and I À (3HOI / IO À 3 þ 2I À þ 3H þ, k ¼ 0.3 M À1 s À1 (Bichsel and Von Gunten, 2000), (ii) reacts with oxidant to from IO À 3 , and (iii) react with natural organic matter, one of the main constituents of water, to produce iodinated DBPs. ...
... Under the conditions of treatment, HOI may go through different processes: (i) disproportionate to IO À 3 and I À (3HOI / IO À 3 þ 2I À þ 3H þ, k ¼ 0.3 M À1 s À1 (Bichsel and Von Gunten, 2000), (ii) reacts with oxidant to from IO À 3 , and (iii) react with natural organic matter, one of the main constituents of water, to produce iodinated DBPs. HOI may also react rapidly with O 3 and chlorine to from IO À 3 (k(HOI þ O 3 ) ¼ 3.6 Â 10 4 M À1 s À1 and k(HOI þ HOCl) ¼ 5.2 Â 10 1 M À1 s À1 (Liu et al., 2014)). Therefore, formation of iodinated DBPs is less during ozonation and chlorination. ...
... Oxidation of I À by chlorine in water in the presence of CuO also gave IO 3 À [137]. The formation rate of IO 3 À significantly increased due to CuO in the system [137]. ...
... Oxidation of I À by chlorine in water in the presence of CuO also gave IO 3 À [137]. The formation rate of IO 3 À significantly increased due to CuO in the system [137]. The formation rates of IO 3 À also increased with an increase in the Br À concentration in the HOCl-I À -Br À -CuO system [137]. ...
... The formation rate of IO 3 À significantly increased due to CuO in the system [137]. The formation rates of IO 3 À also increased with an increase in the Br À concentration in the HOCl-I À -Br À -CuO system [137]. This is not surprising because HOBr has higher reactivity than HOCl (see Table 3). ...
Article
Global production of engineered nanoparticles (ENPs) continues to increase due to the demand of enabling properties in consumer products and industrial applications. Release of individual or aggregates of ENPs have been shown to interact with one another subsequently resulting in adverse biological effects. This review focuses on silver nanoparticles (AgNPs), which are currently used in numerous applications, including but not limited to antibacterial action. Consequently, the release of AgNPs into the aquatic environment, the dissociation into ions, the binding to organic matter, reactions with other metal-based materials, and disruption of normal biological and ecological processes at the cellular level are all potential negative effects of AgNPs usage. The potential sources of AgNPs includes leaching of intact particles from consumer products, disposal of waste from industrial processes, intentional release into contaminated waters, and the natural formation of AgNPs in surface and ground water. Formation of natural AgNPs is greatly influenced by different chemical parameters including: pH, oxygen levels, and the presence of organic matter, which results in AgNPs that are stable for several months. Both engineered and natural AgNPs can interact with metal and metal oxide particles/nanoparticles. However, information on the chemical and toxicological interactions between AgNPs and other nanoparticles is limited. We have presented current knowledge on the interactions of AgNPs with gold nanoparticles (AuNPs) and titanium dioxide nanoparticles (TiO2 NPs). The interaction between AgNPs and AuNPs result in stable bimetallic Ag-Au alloy NPs. Whereas the interaction of AgNPs with TiO2 NPs under dark and light conditions results in the release of Ag⁺ ions, which may be subsequently converted back into AgNPs and adsorb on TiO2 NPs. The potential chemical mechanisms and toxic effects of AgNPs with AuNPs and TiO2 NPs are discussed within this review and show that further investigation is warranted.
... Similar to chlorine, it was found that CuO complexed with HOBr/OBr − and induced a catalytic disproportionation of HOBr that led to the production of bromate (Liu et al., 2012). Chlorination of iodide-containing waters in the presence of CuO also exhibited a catalytic formation of iodate and periodate (Liu et al., 2014). In addition, in the presence of 0.1 g/L CuO, the catalytic decay of chlorine dioxide was 4-5 orders of magnitude faster than when CuO was not present (Liu et al., 2013b). ...
... The impact of CuO dosage ranging from 0 to 1.0 g/L, pH ranging from 6.5 to 8.0, and bromide concentration ranging from 10 to 80 μM on NH 2 Cl stability were investigated. The CuO dosage ranged from 0 to 1.0 g/L, based on previous studies to be able to investigate the reaction kinetics in a reasonable time frame (Hu et al., 2017;Hu et al., 2016;Huang et al., 2019;Li et al., 2007;Liu and Croué, 2016;Liu et al., 2014;Liu et al., 2013aLiu et al., , 2013bLiu et al., 2012;Zhang and Andrews, 2012). ...
... After a reaction time of 54 h, 0.2, 0.5 and 1.0 g/L CuO led to a decrease of NH 2 Cl of 12.5%, 14.7% and 14.0%, respectively, which is similar to NH 2 Cl self-decay (13.6%). This is different from the CuO-catalysed decay observed for HOCl, HOBr, HOI and ClO 2 decomposition (Liu et al., 2014;Liu et al., 2013aLiu et al., , 2013bLiu et al., 2012). At pH 6.5, NHCl 2 is formed at low concentration ( Fig. S1b), indicating that the total oxidant consisted of NH 2 Cl and NHCl 2 . ...
Article
Copper oxide (CuO), a common corrosion product found in copper pipes, has been shown to catalyse the decay of different oxidants in drinking water, including chlorine, bromine, iodine, and chlorine dioxide. However, its impact on monochloramine (NH2Cl), a disinfectant commonly used in long distribution system worldwide is still unknown. In this study, the effect of CuO on NH2Cl decay in the absence or presence of bromide was investigated. Results showed that in the presence of CuO and the absence of bromide, NH2Cl slightly decayed under acidic conditions. When bromide was present in NH2Cl solutions, the total oxidant concentration (sum of the different bromo-chloro-amines) was significantly decreased by CuO. This was primarily due to the degradation of bromochloramine (NHBrCl) by CuO which was evidenced by membrane inlet mass spectrometry. The decomposition rate of the total oxidant was similar for different CuO dosages (0.02–0.2 g/L) but increased with increasing bromide concentration (0–80 μM) and decreasing pH (6.5–8). An apparent second-order rate constant of 0.73 M⁻¹ s⁻¹ was determined with respect to NH2Cl and bromide concentrations for a CuO concentration of 0.05 g/L. Our findings suggest that, during water transportation in copper pipes or in distribution systems where copper oxide is present, special attention should be given to the stability of chloramines when bromide-containing waters are chloraminated.
... Oxidation of I À by chlorine in water in the presence of CuO also gave IO 3 À [137]. The formation rate of IO 3 À significantly increased due to CuO in the system [137]. ...
... Oxidation of I À by chlorine in water in the presence of CuO also gave IO 3 À [137]. The formation rate of IO 3 À significantly increased due to CuO in the system [137]. The formation rates of IO 3 À also increased with an increase in the Br À concentration in the HOCl-I À -Br À -CuO system [137]. ...
... The formation rate of IO 3 À significantly increased due to CuO in the system [137]. The formation rates of IO 3 À also increased with an increase in the Br À concentration in the HOCl-I À -Br À -CuO system [137]. This is not surprising because HOBr has higher reactivity than HOCl (see Table 3). ...
Article
Disinfection of drinking water is important to prevent microbial infection and disease. However, chlorine as a disinfectant is capable of reacting with inorganic and organic constituents of water to produce hazardous chlorinated disinfection byproducts (Cl-DBPs). Brominated and iodinated DBPs (Br-DBPs and I-DBPs), which are more genotoxic and cytotoxic than their chlorinated analogs, may also be formed in the presence of bromide (Br⁻) and iodide (I⁻) in water. This paper first reviews the formation of Cl-DBPs and Br-DBPs by considering the rates of the reactions of chlorine with natural organic matter (NOM) and its model compounds. The reactions of chlorine with Br⁻ and I⁻ yield acids (HOBr/OBr⁻ and HOI/OI⁻, respectively), which subsequently either disproportionate or react with NOM to form Br-DBPs and iodate/I-DBPs, respectively. The mechanisms of the formation of DBPs in the presence of metal ions and metal oxides (which already exist in water and are released from pipes) and nanoparticles (NPs) (input from the use of consumer products) are then reviewed. Water parameters (pH, cationic and anionic constituents, and types and concentration of NOM) also influence the production of DBPs. Plausible mechanisms of the influence of metal ions on the formation of bromate involve complexation of metal ions with moieties of NOM. Metal oxides catalyze the reactions accountable for the formation of Br-DBPs. Only a few studies have been conducted on the effect of NPs on DBP production during chlorination. More research is needed to understand the variation in NP chemistry under environmental conditions (pH, dissolution, and light), and whether NPs influence DBP formation during chlorination.
... In addition to four trihalomethanes (THM4) and five haloacetic acids (HAA5), which are currently regulated by the United States Environmental Protection Agency (US EPA) (U.S. Environmental Protection Agency, 2001), unregulated DBPs including haloacetaldehydes (HALs), haloketones (HKs), haloacetonitriles (HANs), and halonitromethanes (HNMs) were of particular concern due to their much higher toxicity even though their concentrations are much lower than regulated DBPs . Bromide (Br À ) and iodide (I À ) levels in fresh surface waters which are highly variable range from <10 to >1000 mg/L and 0.5e20 mg/L, respectively (Liu et al. 2012(Liu et al. , 2014. However, the median concentrations of Br À and total iodine (including I À and iodate) are much higher in seawater (e.g., ca. ...
... However, the median concentrations of Br À and total iodine (including I À and iodate) are much higher in seawater (e.g., ca. 66 mg/L and 60 mg/ L, respectively) (Heeb et al., 2014;Liu et al., 2014). In addition, anthropogenic activities such as hydraulic fracturing, coal-fired power plants, and wastewater effluent discharge may lead to the elevated halide concentrations in the downstream surface waters (Good and VanBriesen, 2016;Harkness et al., 2015;Vidic et al., 2013). ...
... However, in chlorination system (in the presence of Br À ), the latter pathway is much faster. Based on kinetic model calculations (Liu et al., 2014), the calculated times for the transformation of 90% of initial I À to IO 3 À are 24, 14, 6, 4, and 2 min for [Br À ] 0 ¼ 0, 0.5, 2.5, 5.0, and 10 mM, respectively. This time range was certainly not enough for HOI reactions with AOM to produce a significant amount of I-DBPs, and therefore iodate was the main sink. ...
Article
Seasonal algal blooms in freshwater and marine water can increase the input of algal organic matter (AOM) to the pool of dissolved organic matter. The impact of bromide (Br-) and iodide (I-) on the formation of regulated and unregulated disinfection byproducts (DBPs) was studied from chlorination of AOM solutions extracted from three species of cultured isolates of freshwater and marine algae (Microcystis aeruginosa (MA), Synechococcus (SYN), and Alexandrium tamarense (AT)). Comparable concentrations of DBPs were formed from three types of AOM. In the absence of Br-, trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetaldehydes (HALs) were the main groups of DBP formed, and haloacetonitriles (HANs) were formed at lower concentrations. In contrast, the formation of iodinated THMs was <8 nM (1.7 μg/L) since most of initial I- was oxidized to iodate. Increasing initial Br- concentrations increased the formation of THMs and HANs, while concentrations of total organic halogen and HAA remained stable. On the contrary, total HAL concentrations decreased due to the instability of bromated HALs. Decreasing the specific UV absorbance (SUVA) value of AOM favours bromine substitution since bromine more preferentially reacts with low reactivity organic matter than chlorine. Increasing the pH enhanced the formation of THMs but decreased the formation of HANs. Concentrations of HANs and HALs decreased at high pH (e.g., 9.0), high initial chlorine concentration and long reaction time due to the decomposition. Based on the cytotoxicity calculations, unregulated HANs and HALs were the main contributors for the total toxicity of DBPs measured, even though based on the weight regulated THMs and HAAs predominated.
... In fresh waters, concentrations of I − generally range from 0.5 to 20 μg L −1 . 16 Levels of bromide (Br − ), which usually is simultaneously present with I − , are highly variable in raw waters with a range from <10 to >1000 μg L −1 . 17 For example, a survey over 23 water supplies in the United Staes and Canada showed that Br − and I − in water resources ranged from 24 to 1120 μg L −1 (median: 109 μg L −1 ) and from 0.4 to 104 μg L −1 (median: 10.3 μg L −1 ), respectively. ...
... 11,21−30 In the chlorination process, HOCl/HOBr can oxidize HOI to nontoxic iodate (IO 3 − ), mitigating the formation of I-DBPs. 16 In contrast, after rapid oxidation of I − to HOI, chloramines do not further oxidize HOI to IO 3 − . Therefore, the HOI reaction with DOM leading to the formation of I-DBPs is the major pathway in the chloramination process. ...
... As elevated halide levels are being reported in surface waters due to industrial wastewater discharge, hydraulic fracturing and saltwater intrusion ( Elimelech and Phillip, 2011 ;Good and VanBriesen, 2016 ;Watson et al., 2012 ), increasing bromine incorporation into formed DBPs during chlorination process has been observed in recent years. Since chlorine can further oxidize HOI to nontoxic iodate (IO 3 − ), IO 3 − is the main sink in chlorination process ( Liu et al., 2014 ). On the contrary, chloramines can rapidly oxidize I − to hypoiodous acid (HOI) but do not further oxidize HOI to the nontoxic iodate, leading to the formation of I-DBPs. ...
Article
Algal blooms and wastewater effluents can introduce algal organic matter (AOM) and effluent organic matter (EfOM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts (DBPs) during chlorination and chloramination from various types of dissolved organic matter (DOM, e.g., natural organic matter (NOM), AOM, and EfOM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was observed in NOM than AOM and EfOM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes (HALs), haloacetonitriles (HANs) and haloacetamides (HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor (BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance (SUVA) increased. AOM favored the formation of iodinated THMs (I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor (ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.
... Metals (Cu(II) and Fe(II)) have been shown to enhance the decomposition rate of monochloramine (Fu et al., 2009a(Fu et al., , 2009bVikesland and Valentine, 2000). Copper oxide (CuO) has been extensively investigated as it can catalyse oxidants (ClO 2 , NH 2 Cl, HOCl, and HOBr) decay in the drinking water distribution pipeline (Hu et al., 2021a;Liu et al., 2014Liu et al., , 2013aLiu et al., 2012;Zhang et al., 2008b). For example, CuO catalysed HOCl and HOBr disproportionation, leading to the formation of toxic chlorite, chlorate and bromate (Liu et al., 2013a(Liu et al., , 2012. ...
Article
This study demonstrates that Cu(II) can significantly enhance the decomposition rate of bromamines. Apparent second order rate constants of 2.31 ± 0.01 M⁻¹s⁻¹ and 0.36 ± 0.01 M⁻¹s⁻¹ at pH 7.5 were determined for the reaction of Cu(II) with bromamines and the self-decomposition of bromamines, respectively. Increasing the pH from 6.0 to 8.5, the rate of bromamines self-decomposition decreased while the rate of Cu(II)-catalysed decomposition of bromamines increased. Species-specific rate constants indicated that Cu(OH)2 was the most reactive copper species towards NH2Br and NHBr2. Experiments were carried out with ¹⁵N-labeled bromamines to analyze the nitrogenous degradation products of bromamines in the presence and absence of Cu(II). Nitrogen gas (N2) was found to be the major product from the self-decomposition of bromamines, with N2O, NO2⁻, and NO3⁻ as additional minor products. When Cu(II) was present, the product distribution changed and NO2⁻ and N2O became significant, while N2 and NO3⁻ were produced at low levels. Increasing the Cu(II) concentration from 1.0 to 5.0 mg/L increased the N2O production while decreased the NO2⁻ formation. Based on these results, a mechanism for Cu(II)-catalysed decomposition of bromamines is proposed. This work provides new insights related to the chemistry of bromamines in chloraminated drinking water distribution systems where copper is present.
... In addition, I-DBPs can also be formed in the distribution systems. The residual I − (from the raw water) and disinfectants can undergo a series of chemical reactions with the transition metal oxides (such as CuO, MnO 2 , and PbO 2 ) formed in the pipes, contributing to the formation of I-DBPs in drinking water (Allard et al., 2009;Liu et al., 2014). A previous study has indicated that coagulation of iodide-enriched water with ferric salts may lead to an increase in iodinated organic compounds (Ding et al., 2019). ...
Article
Odors and tastes have become universal problems related to drinking water quality. In addition to the typical odor problems caused by algae or microorganisms, the occurrence of odors derived from drinking water disinfection have attracted attention. The chlor(am)ination-derived odor substances have certain toxicity and odor-causing characteristics, and would enter the tap water through water distribution systems, directly affecting drinking water safety and customer experience. This study provided a comprehensive overview of the occurrence, detection, and control of odor substances derived from drinking water chlor(am)ination disinfection. The occurrence and formation mechanisms of several typical types of disinfection derived odor substances were summarized, including haloanisoles, N-chloroaldimines, iodotrihalomethanes, and halophenoles. They are mainly derived from specific precursors such as halophenols, anisoles, and amino acids species during the disinfection or distribution networks. In addition, the change of disinfectant during chlor(am)ination was also one of the causes of disinfection odors. Due to the extremely low odor threshold concentrations (OTCs) of these odor substances, the effective sample pre-enrichment for instrument identification and quantification are essential. The control strategies of odor problems mainly include adsorption, chemical oxidation, and combined processes such as ozonation and biological activated carbon processes (O3/BAC) and ultraviolet-based advanced oxidation processes (UV-AOPs). Finally, the challenges and possible future research directions in this research field were discussed and proposed.
... Cytoxicity of diiodoacetic acid (DIAA) is approximately 2 and 34 folder higher than that of dibromoacetic acid (DBAA) and dichloroacetic acid (DCAA), respectively (Khiari et al., 1999;Plewa et al., 2002). Therefore, formation of I-DBPs has caused increasing concerns in water treatment, although their yields are significantly less than that of Cl-DBPs and Br-DBPs (Plewa et al., 2004, Richardson et al., 2008Ding and Zhang, 2009;Plewa and Wagner, 2009;Ye et al., 2013;Liu et al., 2014). ...
Article
Formation of halogenated disinfection by-products (DBPs) in sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable concerns recently. Previous studies have focused on the formation of chlorinated and brominated DBPs. This research examined the transformation of I- in heat activated PS oxidation process. Phenol was employed as a model compound to mimic the reactivity of dissolved natural organic matter (NOM) toward halogenation. It was found that I- was transformed to free iodine which attacked phenol subsequently leading to iodinated DBPs such as iodoform and iodoacetic acids. Iodophenols were detected as the intermediates during the formation of the iodoform and triiodoacetic acid (TIAA). However, diiodoacetic acid (DIAA) was formed almost concomitantly with iodophenols. In addition, the yield of DIAA was significantly higher than that of TIAA, which is distinct from conventional halogenation process. Both the facts suggest that different pathway might be involved during DIAA formation in SR-AOPs. Temperature and persulfate dose were the key factors governing the transformation process. The iodinated by-products can be further degraded by excessive SO4•− and transformed to iodate. This study elucidated the transformation pathway of I- in SR-AOPs, which should be taken into consideration when persulfate was applied in environmental matrices containing iodine.
... Enhanced HOI disproportionation catalyzed by oxyanions such as borate (buffer), permanganate or copper oxide (the latter two as metal oxides) has been reported previously. 21,49,50 In analogy to the reaction mechanism of permanganate, 21 eqs 6−9 can be proposed for the reaction mechanism of the Fe(VI)catalyzed iodine disproportionation. In the first step (eq 6), Fe VI O 4 2− , a major Fe(VI) species at pH above 7.2 (eq 3), is complexed with HOI forming O 4 −Fe VI −OI 3− . ...
Article
Oxidative treatment of iodide-containing waters can form iodinated disinfection by-products (I-DBPs) that are more toxic than the regulated DBPs. To better understand the fate of iodine during water treatment with ferrate(VI), kinetics, products, and stoichiometries for the reactions of ferrate(VI) with iodide (I⁻) and hypoiodous acid (HOI) were determined. Ferrate(VI) showed considerable reactivities to both I⁻ and HOI with higher reactivities at lower pH. Interestingly, the reaction of ferrate(VI) with HOI (k = 6.0×10³ M⁻¹s⁻¹ at pH 9) was much faster than with I⁻ (k = 5.6×10 M⁻¹s⁻¹ at pH 9). The main reaction pathway during treatment of I⁻-containing waters was the oxidation of I⁻ to HOI and its further oxidation to IO3⁻ by ferrate(VI). However, for pH > 9, the HOI disproportionation catalyzed by ferrate(VI) became an additional transformation pathway forming I⁻ and IO3⁻. The reduction of HOI by hydrogen peroxide (k = 2.0×10⁸ M⁻¹s⁻¹ for the reaction, HOI + HO2⁻ → I⁻ + O2 + 2H⁺), the latter being produced from ferrate(VI) decomposition, also contributes to the I⁻ 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⁻ system. Overall, due to a rapid oxidation of I⁻ to IO3⁻ with short-lifetimes of HOI, ferrate(VI) oxidation appears to be a promising option for I-DBP mitigation during treatment of I⁻-containing waters.
Article
Previous studies showed that significant bromate (BrO3-) can be formed via the CuO-catalyzed disproportionation of hypobromous acid (HOBr) pathway. In this study, the influence of CuO on the formation of BrO3- and halogenated disinfection byproducts (DBPs) (e.g., trihalomethanes, THMs and haloacetic acids, HAAs) during chlorination of six dissolved organic matter (DOM) isolates was investigated. Only in the presence of slow reacting DOM (from treated Colorado River water, i.e., CRW-BF-HPO), significant BrO3- formation is observed, which competes with bromination of DOM (i.e., THM and HAA formation). Reactions between HOBr and 12 model compounds in the presence of CuO indicates that CuO-catalyzed HOBr disproportionation is completely inhibited by fast reacting phenols, while it predominates in the presence of practically unreactive compounds (acetone, butanol, propionic, and butyric acids). In the presence of slow reacting di- and tri-carboxylic acids (oxalic, malonic, succinic, and citric acids), BrO3- formation varies, depending on its competition with bromoform and dibromoacetic acid formation (i.e., bromination pathway). The latter pathway can be enhanced by CuO due to the activation of HOBr. Therefore, increasing CuO dose (0-0.2 g L-1) in a reaction system containing chlorine, bromide, and CRW-BF-HPO enhances the formation of BrO3-, total THMs and HAAs. Factors including pH and initial reactant concentrations influence the DBP formation. These novel findings have implications for elevated DBP formation during transportation of chlorinated waters in copper-containing distribution systems.
Article
Dichloroacetamide (DCAcAm), a disinfection byproduct, has been detected in drinking water. Previous research showed that amino acids may be DCAcAm precursors. However, other precursors may be present. This study explored the contribution of the antibiotic chloramphenicol (CAP) and two of its analogues (thiamphenicol, TAP; florfenicol, FF), referred to collectively as CAPs, which occur in wastewater-impacted source waters, to the formation of DCAcAm. Their formation yields were compared to free and combined amino acids, and they were investigated in filtered waters from drinking water treatment plants, heavily wastewater-impacted natural waters, and secondary effluents from wastewater treatment plants. CAPs had greater DCAcAm formation potential than two representative amino acid precursors. However, in drinking waters with ng/L levels of CAPs, they will not contribute as much to DCAcAm formation as the µg/L levels of amino acids. Also, the effect of advanced oxidation processes (AOPs) on DCAcAm formation from CAPs in real water samples during subsequent chlorination was evaluated. Pre-oxidation of CAPs with AOPs reduced the formation of DCAcAm during post-chlorination. Trichloronitromethane was also formed from CAP, but not from TAP or FF. The results of this study suggest that CAPs should be considered as possible precursors of DCAcAm, especially in heavily wastewater-impacted waters.
Article
Oxidation kinetics of iodide and HOI/OI- by permanganate were studied in the pH range 5-10. Iodide oxidation and iodate formation were faster at lower pH. The apparent second order rate constants (kobs) for iodide oxidation by permanganate decrease with increasing pH from 29 M-1s-1 at pH 5, 6.9 M-1s-1 at pH 7, to 2.7 M-1s-1 at pH 10. kobs for HOI abatement are 56 M-1s-1 at pH 5, 2.5 M-1s-1 at pH 7 and 173 M-1s-1 at pH 10. Iodate yields over HOI abatement decrease from 98% at pH 6 to 33% for pH ≥ 9.5, demonstrating that HOI disproportionation dominates HOI transformation by permanganate at pH ≥ 8. MnO2 forms as a product from permanganate reduction, oxidizes HOI to iodate for pH < 8 and promotes HOI disproportionation for pH  8. The HOI oxidation or disproportionation induced by MnO2 is not comparable to permanganate. During treatment of iodide containing waters, the potential for the I-DBPs formation is highest at pH 7-8 due to the long lifetime of HOI. For pH  6, HOI/I2 is quickly oxidized by permanganate to iodate whereas for pH  8, HOI/OI- undergoes a fast permanganate-mediated disproportionation.
Article
Lead oxide (PbO2) formed by the oxidation of lead pipes and lead-containing plumbing materials is an important corrosion product in some drinking water distribution systems. Under certain conditions it acts as an oxidant, and we report here the effects of pH on the oxidation of I¯ by PbO2, which leads to the formation of iodine (I2) and iodate (IO3¯) as well as dissolution of Pb²⁺. Oxidation of I¯ by PbO2 is a multi-step pH-dependent reaction, the rate of which can be expressed as: R = 6.92 × 10⁹ × [SA]0.67 × [I¯]2.19 × [H⁺]0.59 (where SA is the PbO2 surface area). I2 was the major intermediate product formed along with some HOI, and was then further oxidized to IO3¯. Based on these results, a kinetic model was developed to simulate the evolution of I¯, I2 and IO3¯ in the PbO2/I¯ reaction system. In addition, the formation of iodinated disinfection by-products (I-DBPs) in the PbO2/I¯/NOM system was evaluated under different water quality conditions, and was found to be influenced by the form of the lead corrosion products in the order: Pb3O4 > PbO2 > Pb(CO3)2(OH)2 > PbCO3. Iodoform and monoiodoacetic acid were identified as the main I-DBPs, and their formation decreased with increasing pH. It is concluded that oxidation of I¯ by lead oxides in water distribution pipes probably contributes to the formation of I-DBPs as well as Pb²⁺ in tap water.
Article
ConspectusFormation of iodinated disinfection byproducts (I-DBPs) in drinking water has become an emerging concern. Compared to chlorine- and bromine-containing DBPs, I-DBPs are more toxic, have different precursors and formation mechanisms, and are unregulated. In this Account, we focus on recent research in the formation of known and unknown I-DBPs in drinking water. We present the state-of-the-art understanding of known I-DBPs for the six groups reported to date, including iodinated methanes, acids, acetamides, acetonitriles, acetaldehyde, and phenols. I-DBP concentrations in drinking water generally range from ng L ⁻¹ to low-μg L ⁻¹ . The toxicological effects of I-DBPs are summarized and compared with those of chlorinated and brominated DBPs. I-DBPs are almost always more cytotoxic and genotoxic than their chlorinated and brominated analogues. Iodoacetic acid is the most genotoxic of all DBPs studied to date, and diiodoacetamide and iodoacetamide are the most cytotoxic. We discuss I-DBP formation mechanisms during oxidation, disinfection, and distribution of drinking water, focusing on inorganic and organic iodine sources, oxidation kinetics of iodide, and formation pathways. Naturally occurring iodide, iodate, and iodinated organic compounds are regarded as important sources of I-DBPs. The apparent second-order rate constant and half-lives for oxidation of iodide or hypoiodous acid by various oxidants are highly variable, which is a key factor governing the iodine fate during drinking water treatment. In distribution systems, residual iodide and disinfectants can participate in reactions involving heterogeneous chemical oxidation, reduction, adsorption, and catalysis, which may eventually affect I-DBP levels in finished drinking water. The identification of unknown I-DBPs and total organic iodine analysis is also summarized in this Account, which provides a more complete picture of I-DBP formation in drinking water. As organic DBP precursors are difficult to completely remove during the drinking water treatment process, the removal of iodide provides a cost-effective solution for the control of I-DBP formation. This Account not only serves as a reference for future epidemiological studies to better assess human health risks due to exposure to I-DBPs in drinking water but also helps drinking water utilities, researchers, regulators, and the general public understand the formed species, levels, and formation mechanisms of I-DBPs in drinking water.
Article
The increasing occurrence of harmful algal blooms in surface waters may increase the input of algal organic matter (AOM) to the dissolved organic matter pool. The formation of iodinated trihalomethanes (I-THMs) and noniodinated disinfection byproducts (DBPs) in synthetic waters containing AOM extracted from Microcystis aeruginosa was investigated in chloramination (preformed and in-situ formed chloramine, NH2Cl and Cl2-NH2Cl, respectively) and chlorination (Cl2) processes. AOM is much more favorable for iodine incorporation than natural organic matter (NOM). For example, the formation of I-THM from AOM is much higher than NOM isolate extracted from treated water (e.g., 3.5 times higher in the NH2Cl process), and thus higher iodine utilization and substitution factors from AOM were observed. Short contact time (2 min) chlorination in Cl2-NH2Cl process leading to the formation of halogenated intermediates favored I-THM formation, compared with NH2Cl process. However, further increasing chlorine contact time from 5 min to 24 h facilitated the conversion from iodide to iodate and thus I-THM formation decreased. Meanwhile, the formation of noniodinated THM4, haloacetonitriles (HANs), and haloacetaldehydes (HALs) increased. Factors including concentrations of AOM and bromide, pH, and chlorine/nitrogen ratios influenced the formation of I-THMs and noniodinated DBPs. To evaluate the benefit of mitigating I-THM formation over the risk of noniodinated DBP formation, measured DBPs were weighed against their mammalian cell toxicity indexes. Increasing the chlorine exposure increased the calculated cytotoxicity based on concentrations of measured I-THMs and noniodinated DBPs since unregulated HANs and HALs were the controlling agents.
Article
In this study, the formation of iodinated trihalomethanes (I-THMs) was systematically evaluated and compared for three treatment processes - (i) chlorination, (ii) monochloramine, and (iii) dichloramination - under different pH conditions. The results demonstrated that I-THM formation decreased in the order of monochloramination > dichloramination > chlorination in acidic and neutral pH. However, the generation of I-THMs increased in the dichloramination < chlorination < monochloramination order in alkaline condition. Specifically, the formation of I-THMs increased as pH increased from 5 to 9 during chlorination and monochloramination processes, while the maximum I-THM formation occurred at pH 7 during dichloramination. The discrepancy could be mainly related to the stability of the three chlor (am) ine disinfectants at different pH conditions. Moreover, in order to gain a thorough insight into the mechanisms of I-THM formation during dichloramination, further investigation was conducted on the influencing factors of DOC concentration and Br⁻/I⁻ molar ratio. I-THM formation exhibited an increasing and then decreasing trend as the concentration of DOC increased from 1 to 7 mg-C/L, while the yield of I-THMs increased with increasing Br⁻/I⁻ molar ratio from 5: 0 to 5: 10. During the three processes mentioned above, similar I-THM formation results were also obtained in real water, which indicates that the excessive generation of I-THMs should be paid special attention during the disinfection of iodide-containing water.
Article
The effects of organic amines (OAs) including glycine (Gly), sarcosine (Sar) and triethanolamine (Tea), representing primary, secondary and tertiary amines, respectively, on iodinated trihalomethanes (I-THMs) formation during chlorination of iodide (I‒)-containing waters were investigated. The total concentration of I-THMs formed in the co-presence of an OA and natural organic matter (NOM) was more than 3 times the sum of those formed in the presence of an OA alone and NOM alone, as OAs competed for free chlorine (FC) to form organic chloramines. Taking Gly as an example, the transformation of I‒ was determined. In the absence of NOM, the yields of iodate (IO3‒) were 89%, 60% and nearly 0 at [Gly]o/[FC]o = 0:1, 3:4 and 1:1, but 0, 2% and 43% for hypoiodous acid (HOI), respectively. In the presence of NOM, as [Gly]o/[FC]o increased from 0:1 to 1:1, the yield of IO3‒ decreased from 66% to 0, while that of I-THMs increased from 2.9% to 16.1%. The competition of FC by OAs inhibited the oxidation of HOI to IO3‒ and the formed organic chloramines oxidized I‒ to HOI, thus promoting I-DBPs formation. Finally, the enhanced I-THMs formation was verified in real waters.
Article
Residual manganese(II) in finished water undergoes further oxidation and deposition in drinking water distribution systems (DWDS), and Mn deposits can function as sites for accumulating organic and inorganic pollutants. This study aims to explore how Mn transformation and deposition affect the formation of disinfection byproducts (DBPs) in chlorinated DWDS, and trihalomethanes (THMs) was selected as a representative DBP. In a 100 μg/L Mn system, regulated THMs (chlorinated/bromated-THMs) increased by over 20% higher than Mn-free system after 150-day operation; when 50 μg/L iodide (I⁻) entered pipe systems after 150 days, iodinated THMs (I-THMs) in 100 μg/L Mn system increased by over 30% compared with Mn-free system. These promotions were attributed primarily to the accumulation of biomolecules and organic substances by tight and hard chlorinated Mn deposits, which, our results suggested that the residence of inactivated cells and the bridging role of surface Mn(III) in Mn deposits increased the quantity of THM precursors in DWDS. Furthermore, the rapid catalytic oxidation of Mn(II) by formed Mn oxides (MnOx) inhibited the conversion of free iodine (HOI/OI⁻) to iodate, resulting in the generation of more I-THMs. This study provides new insights into the DBP risks caused by Mn in DWDS.
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Iodine is a naturally-occurring halogen in natural waters generally present in concentrations between 0.5 and 100 µg L⁻¹. During oxidative drinking water treatment, iodine-containing disinfection by-products (I-DBPs) can be formed. The formation of I-DBPs was mostly associated to taste and odor issues in the produced tap water but has become a potential health problem more recently due to the generally more toxic character of I-DBPs compared to their chlorinated and brominated analogues. This paper is a systematic and critical review on the reactivity of iodide and on the most common intermediate reactive iodine species HOI. The first step of oxidation of I⁻ to HOI is rapid for most oxidants (apparent second-order rate constant, kapp > 10³ M⁻¹s⁻¹ at pH 7). The reactivity of hypoiodous acid with inorganic and organic compounds appears to be intermediate between chlorine and bromine. The life times of HOI during oxidative treatment determines the extent of the formation of I-DBPs. Based on this assessment, chloramine, chlorine dioxide and permanganate are of the highest concern when treating iodide-containing waters. The conditions for the formation of iodo-organic compounds are also critically reviewed. From an evaluation of I-DBPs in more than 650 drinking waters, it can be concluded that one third show low levels of I-THMs (<1 µg L⁻¹), and 18% of exhibit concentrations > 10 µg L⁻¹. The most frequently detected I-THM is CHCl2I followed by CHBrClI. More polar I-DBPs, as iodoacetic acid in particular, have been reviewed as well. Finally, the transformation of iodide to iodate, a safe iodine-derived end-product, has been proposed to mitigate the formation of I-DBPs in drinking water processes. For this purpose a pre-oxidation step with either ozone or ferrate(VI) to completely oxidize iodide to iodate is an efficient process. Activated carbon has also been shown to be efficient in reducing I-DBPs during drinking water oxidation.
Article
Copper water pipelines are widely used in water distribution systems, but the effects of solid copper corrosion products (CCPs) including CuO, Cu2O and Cu2(OH)2CO3 on the generation of iodinated trihalomethanes (I-THMs) during chloramination remain unknown. This study found that the formation of I-THMs during chloramination of humic acid (HA) was inhibited by the presence of CuO and Cu2O, but promoted with the addition of Cu2(OH)2CO3. The negative effect of CuO and Cu2O is mainly exerted by promoting the decay of both NH2Cl and HOI. Although Cu2(OH)2CO3 also accelerated the decomposition of NH2Cl and HOI, it was found that the complexes formed between Cu2(OH)2CO3 and HA facilitated, through carboxyl functional groups, the reaction between HA and HOI, leading to an enhancement of I-THM generation during chloramination, which was further confirmed by model compound experiments. Additionally, this study demonstrated that the effects of solid CCPs on I-THMs generation during chloramination were solid CCP- and HA-concentration dependent, but almost unaffected by different initial I⁻ and Br⁻ concentrations. This study provides new insights into the health risks caused by the corrosion of copper water pipelines, especially in areas intruded by sea water.
Article
The formation of iodinated disinfection byproducts (I-DBPs) in drinking waters is of a concern due to their higher cyto- and genotoxicity than their chlorinated and brominated analogues. This study investigated the formation of I-DBPs under chloramination conditions using preformed chloramine and associated cyto- and geno-toxicities obtained with Chinese Hamster Ovary (CHO) cell assay. Cyto- and geno-toxicity of the samples were also calculated using DBP toxicity index values and correlated with total organic halide (TOX) formation. In low iodide (I-) (0.32 μM, 40 μg L-1) water, increasing dissolved organic carbon (DOC) concentration of selected waters from 0.1 to 0.25 mg L-1 increased the formation of iodinated trihalomethanes (I-THMs), while further increases from 0.25 to 4 mg L-1 produced an opposite trend. In high iodide water (3.2 μM, 400 μg L-1), increasing DOC from 0.5 to 4 mg L-1 gradually increased the I-THM formation, while a decrease was observed at 5.4 mg L-1 DOC. Iodoform was the most influenced species from the changes in DOC concentration. While increasing the initial iodide concentration from 0 to 5 μM increased the formation of iodoform, it did not make any considerable impact on the formation of other I-THMs. The measured cytotoxicity of samples was significantly correlated with increasing DOC concentration. Unknown TOCl and TOI showed a high correlation with measured cytotoxicity, while calculated total organic chlorine (TOCl) and total organic iodine (TOI) did not correlate. The comparison of measured and calculated cytotoxicity values showed that the calculated values do not always represent the overall cytotoxicity, since the formation of unknown DBPs are not taken into consideration during the toxicity calculations.
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Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect. Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks its concentration is fairly uniform and averages 0.24 mg/kg. Sedimentary rocks tend to have higher concentrations with average iodine contents of:-recent sediments 5–200 mg/kg, carbonates 2.7 mg/kg, shales 2.3 mg/kg and sandstones 0.8 mg/kg. Organic-rich sediments are particularly enriched in iodine. Soils, generally, are much richer in iodine than the parent rocks with the actual level being decided mainly by soil type and locality. Little soil iodine is water-soluble and much iodine is thought to be associated with organic matter, clays and aluminium and iron oxides. Most iodine in soils is derived from the atmosphere where, in turn, it has been derived from the oceans. Seawater has a mean iodine content of 58 μg/L, while non-saline surface waters have lower and very variable levels. Subsurface brines and mineral waters are generally strongly enriched in iodine. Marine plants are frequently enriched in iodine while terrestrial plants have generally low contents. Iodine is essential for all mammals. Consideration of the geochemical cycle of iodine reveals that its transfer from the oceans to the atmosphere is probably the most important process in its geochemistry.
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Iodine in sea water of the Pacific was determined with special interest in the relation between iodide and iodate in the surface water of the ocean. The result was discussed with reference to the mechanism of iodide formation proposed byTsunogai andSase. The concentration of iodide varies widely from the lower value than the detection limit to 0.21g at./l, while the concentration of total iodine is nearly constant and the mean value is 0.41g at./l. The vertical profile of iodide often shows the maximum in the surface layer. In the surface layer, the concentration of iodide is higher in warm water (0,10g at./l on the average) than that in cold water of lower temperature than 20 C (0.03g at/l). The highest concentration of iodide among the warm waters is found in the surface water of the equatorial area (0.13g at./l) where the biological productivity is also high. Iodide is generally more enriched in the water having higher biological activity even in the cold water. These results are considered to be compatible with the mechanism of iodide formation proposed.
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The kinetics of iodate formation is a critical factor in mitigation of the formation of potentially toxic and off flavor causing iodoorganic compounds during chlorination. This study demonstrates that the formation of bromine through the oxidation of bromide by chlorine significantly enhances the oxidation of iodide to iodate in a bromide-catalyzed process. The pH-dependent kinetics revealed species specific rate constants of k(HOBr + IO(-)) = 1.9 × 10(6) M(-1) s(-1), k(BrO(-) + IO(-)) = 1.8 × 10(3) M(-1) s(-1), and k(HOBr + HOI) < 1 M(-1) s(-1). The kinetics and the yield of iodate formation in natural waters depend mainly on the naturally occurring bromide and the type and concentration of dissolved organic matter (DOM). The process of free chlorine exposure followed by ammonia addition revealed that the formation of iodo-trihalomethanes (I-THMs), especially iodoform, was greatly reduced by an increase of free chlorine exposure and an increase of the Br(-)/I(-) ratio. In water from the Great Southern River (with a bromide concentration of 200 μg/L), the relative I-incorporation in I-THMs decreased from 18 to 2% when the free chlorine contact time was increased from 2 to 20 min (chlorine dose of 1 mg Cl(2)/L). This observation is inversely correlated with the conversion of iodide to iodate, which increased from 10 to nearly 90%. Increasing bromide concentration also increased the conversion of iodide to iodate: from 45 to nearly 90% with a bromide concentration of 40 and 200 μg/L, respectively, and a prechlorination time of 20 min, while the I-incorporation in I-THMs decreased from 10 to 2%.
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Because it is more stable than iodide, most health authorities preferentially recommend iodate as an additive to salt for correcting iodine deficiency. Even though this results in a low exposure of at most 1,700 microg/d, doubts have recently been raised whether the safety of iodate has been adequately documented. In humans and rats, oral bioavailability of iodine from iodate is virtually equivalent to that from iodide. When given intravenously to rats, or when added to whole blood or tissue homogenates in vitro or to foodstuff, iodate is quantitatively reduced to iodide by nonenzymatic reactions, and thus becomes available to the body as iodide. Therefore, except perhaps for the gastrointestinal mucosa, exposure of tissues to iodate might be minimal. At much higher doses given intravenously (i.e., above 10 mg/kg), iodate is highly toxic to the retina. Ocular toxicity in humans has occurred only after exposure to doses of 600 to 1,200 mg per individual. Oral exposures of several animal species to high doses, exceeding the human intake from fortified salt by orders of magnitude, pointed to corrosive effects in the gastrointestinal tract, hemolysis, nephrotoxicity, and hepatic injury. The studies do not meet current standards of toxicity testing, mostly because they lacked toxicokinetic data and did not separate iodate-specific effects from the effects of an overdose of any form of iodine. With regard to tissue injury, however, the data indicate a negligible risk of the small oral long-term doses achieved with iodate-fortified salt. Genotoxicity and carcinogenicity data for iodate are scarce or nonexisting. The proven genotoxic and carcinogenic effects of bromate raise the possibility of analogous activities of iodate. However, iodate has a lower oxidative potential than bromate, and it did not induce the formation of oxidized bases in DNA under conditions in which bromate did, and it may therefore present a lower genotoxic and carcinogenic hazard. This assumption needs experimental confirmation by proper genotoxicity and carcinogenicity data. These in turn will have to be related to toxicokinetic studies, which take into account the potential reduction of iodate to iodide in food, in the intestinal lumen or mucosa, or eventually during the liver passage.
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A new method for disinfection of microorganisms by electrochemically regenerated periodate was developed. Oxidation of iodate to periodate was observed at 1.25 V versus a silver/silver chloride electrode in a cyclic voltammogram of potassium iodate. When 1.25 V was applied in 1.0 mM potassium iodate, approximately 4-log inactivation of Escherichia coli was observed in 30 min.
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[1] A spatial survey of iodine and its long-lived isotope, 129I, in 40 rivers of the USA, Canada, and western Europe, reveals that the ratio of 129I/I is a sensitive indicator for the influence of nuclear fuel reprocessing facilities. Rivers with point sources for 129I in their watersheds are drastically affected, while all rivers sampled show evidence for atmospherically transported 129I from the world's major nuclear fuel reprocessing facilities. Varying mixtures of oceanic cyclic salt and soil-derived iodine account for the observed spatial variation in iodine concentrations. A comparison of 129I concentrations in river and rainwater reveals concentration effects due to evapotranspiration.
Article
The dissolved iodine species that dominate aquatic systems are iodide, iodate and organo-iodine. These species may undergo transformation to one another and thus affect the formation of iodinated disinfection byproducts during disinfection of drinking waters or wastewater effluents. In this study, a fast, sensitive and accurate method for determining these iodine species in waters was developed by derivatizing iodide and iodate to organic iodine and measuring organic iodine with a total organic iodine (TOI) measurement approach. Within this method, organo-iodine was determined directly by TOI measurement; iodide was oxidized by monochloramine to hypoiodous acid and then hypoiodous acid reacted with phenol to form organic iodine, which was determined by TOI measurement; iodate was reduced by ascorbic acid to iodide and then determined as iodide. The quantitation limit of organo-iodine or sum of organo-iodine and iodide or sum of organo-iodine, iodide and iodate was 5 μg/L as I for a 40 mL water sample (or 2.5 μg/L as I for an 80 mL water sample, or 1.25 μg/L as I for a 160 mL water sample). This method was successfully applied to the determination of iodide, iodate and organo-iodine in a variety of water samples, including tap water, seawater, urine and wastewater. The recoveries of iodide, iodate and organo-iodine were 91-109%, 90-108% and 91-108%, respectively. The concentrations and distributions of iodine species in different water samples were obtained and compared.
Article
Using seawater for toilet flushing may introduce high levels of bromide and iodide into a city's sewage treatment works, and result in the formation of brominated and iodinated disinfection byproducts (DBPs) during chlorination to disinfect sewage effluents. In a previous study, the authors' group has detected the presence of many brominated DBPs and identified five new aromatic brominated DBPs in chlorinated saline sewage effluents. The presence of brominated DBPs in chlorinated saline effluents may pose adverse implications for marine ecology. In this study, besides the detection and identification of another seven new aromatic halogenated DBPs in a chlorinated saline sewage effluent, their developmental toxicity was evaluated using a marine polychaete Platynereis dumerilii. For comparison, the developmental toxicity of some commonly known halogenated DBPs was also examined. The rank order of the developmental toxicity of 20 halogenated DBPs was 2,5-dibromohydroquinone > 2,6-diiodo-4-nitrophenol ≥ 2,4,6-triiodophenol > 4-bromo-2-chlorophenol ≥ 4-bromophenol > 2,4-dibromophenol ≥ 2,6-dibromo-4-nitrophenol > 2-bromo-4-chlorophenol > 2,6-dichloro-4-nitrophenol > 2,4-dichlorophenol > 2,4,6-tribromophenol > 3,5-dibromo-4-hydroxybenzaldehyde > bromoform ≥ 2,4,6-trichlorophenol > 2,6-dibromophenol > 2,6-dichlorophenol > iodoacetic acid ≥ tribromoacetic acid > bromoacetic acid > chloroacetic acid. Based on the developmental toxicity data, a quantitative structure-activity relationship (QSAR) was established. The QSAR involved two physical-chemical property descriptors (log P and pKa) and two electronic descriptors (the lowest unoccupied molecular orbital energy and the highest occupied molecular orbital energy) to indicate the transport, bio-uptake and bio-interaction of these DBPs. It can well predict the developmental toxicity of most of the DBPs tested.
Article
A number of iodine compounds are studied as solids, in particular some iodine-oxygen and iodine-chlorine compounds and the tri-iodide ion. The chlorine 2p electron binding energy for I2Cl6 can be resolved into two peaks of intensity ratio 2:1 corresponding to terminal and bridging chlorine atoms. The iodine 3d electron binding energy for the tri-iodide ion may be resolved into peaks corresponding to different iodine atoms. The experimental results are compared with CNDO calculations, using both a 5s, 5p(sp model) and a 5s, 5p and 5d(spd model) basis set, in the framework of the ground and relaxation potential models (GPM and RPM). The CNDO calculations (spd model) give good agreement with previously published charges for xenon compounds, and the spd model, but not the sp model, is found to give good agreement with the experimental results for iodine compounds. The RPM model is found to be an improvement over the GPM model. The overall bond orders obtained with the spd model charges and charges based on Pauling electronegativities are compared for the isoelectronic series SiO4–4, PO3–4, SO2–4, ClO–4, and the trends found to be in the opposite directions. For ClO–4, Pauling charges give particularly poor agreement with experiment.
Article
Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate > sulfate > bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO.
Article
The reactivity of hypoiodous acid (HOI) is an important factor for the fate of iodine in oxidative drinking water treatment. The possible reactions of HOI are its disproportionation, its oxidation to iodate (IO−3), or the reaction with natural organic matter (NOM). The latter reaction may result in the formation of iodoorganic compounds which are frequently responsible for taste and odor problems. The acid dissociation constant (pKa) of HOI has been determined spectrophotometrically as 10.4±0.1 (T=25°C; I=50 mM). Kinetic constants and a new rate law for the disproportionation of HOI as catalyzed by hydrogencarbonate, carbonate, and borate are presented. In the pH range 7.6–11.1, the main uncatalyzed reactions are HOI+HOI (k1=0.3 M−1 s−1) and HOI+OI− (k2=15 M−1 s−1). The buffer-catalyzed reaction step was found to be second-order in HOI and first-order in the buffer anion. The following rate constants were deduced: HOI+HOI+HCO−3: 50 M−2 s−1; HOI+HOI+CO2−3: 5000 M−2 s−1; HOI+HOI+B(OH)−4: 1700 M−2 s−1. All these rate constants result in half-lifes for HOI of 10–1000 days under typical drinking water conditions.
Article
Chlorine dioxide (ClO2) decay in presence of typical metal oxides occurring in distribution systems was investigated. The ClO2 decay in presence of metal oxides was generally enhanced in a second-order process via three pathways: 1) catalytic disproportionation with equimolar formation of chlorite and chlorate, 2) reaction to chlorite and oxygen, and 3) oxidation of a metal in a reduced form (e.g., cuprous oxide) to a higher oxidation state. Cupric oxide (CuO) and nickel oxide (NiO) showed significantly stronger abilities than goethite (alpha-FeOOH) to catalyze the ClO2 disproportionation (pathway 1) which predominated at higher initial ClO2 concentrations (56-81 micromole per liter). At lower initial ClO2 concentrations (13-31 micromole per liter) pathway 2 also contributed. The CuO-enhanced ClO2 decay is a base-assisted reaction with a third-order rate constant of 1.5×1000000 M-2s-1 in the presence of 0.1 g L-1 CuO at 21±1 C, which is 4-5 orders of magnitude higher than in absence of CuO. The presence of natural organic matter (NOM) significantly enhanced the formation of chlorite and decreased the ClO2 disproportionation in CuO-ClO2 system, probably due to a higher reactivity of ClO2 adsorbed to CuO with NOM. Furthermore, a kinetic model was developed to simulate CuO-enhanced ClO2 decay at various pHs. Model simulations which agree well with the experimental data include a pre-equilibrium step with the rapid formation of a complex, namely CuO-adsorbed Cl2O4. The reaction of this complex with OH- is the rate-limiting and pH-dependent step for the overall reaction, producing chlorite and an intermediate that further forms chlorate and oxygen in parallel. These novel findings suggest that the possible ClO2 loss and the formation of chlorite/chlorate should be carefully considered in drinking water distribution systems containing copper pipes.
Article
The aim of this work is to assess the performance of different corrosion products as an effective copper corrosion protection in synthetic tap water. The major objective of this study was to evaluate the stability of copper oxide film and naturally formed heterogeneous corrosion products under the influence of synthetic tap water. The influence of copper products on the corrosion behavior in neutral synthetic tap water was investigated using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The EIS plot was changed from two time constants to three time constants due to the enrichment of cuprous oxide (Cu2O) on the copper surface. Copper experienced only uniform corrosion. As the protective oxide film thickened, it did not separate from the copper surface.
Article
The corrosion behaviour of copper in neutral aerated simulated tap water is investigated using electrochemical methods and XPS. Semi-infinite diffusion behaviour is found in electrochemical impedance spectroscopy (EIS) from intermediate to low frequency. Polarization resistance (Rp) obtained at very low frequency (0.0005 Hz) increases with immersion time, which coincides with the growth of oxide film on copper. The growth of oxide film with immersion time has little effect on the cathodic process, but considerably reduces the anodic dissolution current. The observed results suggest that the diffusion of copper ions in oxide film controls the overall corrosion rate. Under rotating conditions polarization resistance decreases and anodic current increases, which was caused by the decrease of the oxide film thickness. The phenomena of the mixed diffusion of copper ion in oxide film and in solution has been observed at a low pH of 5. Passivation is found when pH = 10. XPS spectra show that the oxide film formed is composed mainly of cuprous oxide. An equivalent circuit representing the corroding interface is proposed with a discussion of theoretical approaches to the calculation of diffusion impedance and polarization resistance.
Article
The presence of iodinated disinfection by-products (I-DBPs) in drinking water poses a potential health concern since it has been shown that I-DBPs are generally more genotoxic and cytotoxic than their chlorinated and brominated analogs. I-DBPs are formed during oxidation/disinfection of iodide-containing waters by reaction of the transient hypoiodous acid (HOI) with natural organic matter (NOM). In this study, we demonstrate that ozone pre-treatment selectively oxidizes iodide to iodate and avoids the formation of I-DBPs. Iodate is non-toxic and is therefore a desired sink of iodine in drinking water. Complete conversion of iodide to iodate while minimizing the bromate formation to below the guideline value of 10 μg L(-1) was achieved for a wide range of ozone doses in five raw waters with DOC and bromide concentrations of 1.1-20 mg L(-1) and 170-940 μg L(-1), respectively. Lowering the pH effectively further reduced bromate formation but had no impact on the extent of iodate and bromoform formation (the main trihalomethane (THM) formed during ozonation). Experiments carried out with pre-chlorinated/post-clarified samples already containing I-DBPs, showed that ozonation effectively oxidized I-THMs. Therefore, in iodide-containing waters, in which I-DBPs can be produced upon chlorination or especially chloramination, a pre-ozonation step to oxidize iodide to iodate is an efficient process to mitigate I-DBP formation.
Article
The kinetics of the periodate oxidation of catechol have been investigated over the pH range 0-10. An intermediate was directly observable on a stopped-flow apparatus over the pH range 0.45-7.26. The kinetics of intermediate formation were found to be second order (first order in each reactant concentration), and were adequately explained on the basis of differing reactivities of the various periodate and catechol species present in solution over the pH range 0-10. The intermediate was found to decompose to products in a first-order fashion which was independent of the catechol and periodate concentrations. The observed kinetics of intermediate decomposition were explained by the assumption of a combination of uncatalyzed, specific hydrogen ion and specific hydroxide ion catalyzed paths. Since the maximum half-life of the intermediate was only 2.9 sec, it was not possible to isolate and characterize it. While the assumption of a cyclic diester of periodic acid as the structure of the intermediate is logical in light of the proposed mechanism of periodate oxidation of α-glycols, this postulate does not appear to be supported by all of the experimental evidence now in hand.
Article
The very rapid reaction between HOCl and I - is general-acid- (HA-) assisted. The proposed mechanism is HOCl + I - ⇄ k-1k1 HOClI - HOClI - → k0 HO - + ICl HOClI - + HA → kHA H 2O + ICl + A - ICl + 2I - → fast I 3- + Cl - where a stability constant (k 1/k -1 = 220 M -1) is determined for the HOClI - intermediate from kinetic data and the limiting rate constant at high [H +] is k 1 = 4.3 × 10 8 M -1 s -1. Values for third-order rate constants (with the general form k 1k HA/(k 0 + k -1) (M -2 s -1) at 25.0°C, μ = 0.1) are evaluated for H 3O + (3.5 × 10 11), CH 3COOH (3.2 × 10 10), and H 2PO 4- (2.6 × 10 10) and give a Brønsted α value of 0.11, which indicates a small degree of proton transfer in the transition state. For the H 2O path, k 0k 1/(k 0 + k -1) = 1.4 × 10 8 M -1 s -1. The reaction between trichloramine and iodide exhibits saturation kinetics due to the formation of NCl 3I - (K 1 = 6 × 10 3 M -1), which undergoes first-order decomposition (k 2 = 1.5 × 10 4 s -1 at 25.0°C and μ = 0.1) to HNCl 2 and ICl. Acids do not affect the rate of NCl 3I - decomposition. For these two studies first-order rate constants fall in the range of 10 000-142 000 s -1 and are measured by pulsed-accelerated-flow spectroscopy.
Article
The rate expression for the oxidation of bromide by HOCl and OCl - is -d[OCl -] T/dt = h HA[HA][OCl -] T[Br -], where [OCl -] T = [OCl -] + [HOCl] and HA is a general acid (H 2O, HPO 42-, HCO 3-, CH 3COOH, ClCH 2COOH, or H 3O +). The k HA value for H 3O + + OCl - + Br - is 3.65 × 10 10 M -2 s -1 (this path requires HOCl as an intermediate), while the k HA value for H 3O + + HOCl + Br - is 1.32 × 10 6 M -2 s -1. In terms of second-order expressions, the rate constant for HOCl and Br - is 1.55 × 10 3 M -1 s -1, while the rate constant for OCl - + Br - is only 0.90 × 10 -3 M -1 s -1. The proposed mechanism for the acid-assisted reactions (except for H 3O + + OCl -) is a simultaneous proton transfer (from HA to OCl - or to HOCl) and Cl + transfer to Br - (to give BrCl, which reacts rapidly to give OBr - or Br 2 and Br 3-). The Brønsted α value is 0.75 for the reactions of HA with OCl - and Br -, and the α value is 0.27 for the reactions of HA with HOCl and Br -. The α values reflect the degree of proton transfer in the transition state.
Article
The formation of iodo-trihalomethanes (I-THMs) such as iodoform (CHI3) during oxidative treatment of iodide-containing drinking waters can be responsible for taste and odor problems. I-THMs are formed by reactions of hypoiodous acid (HOI) with natural organic matter. HOI is quickly formed from naturally occurring iodide (I-) by oxidation with ozone, chlorine, or chloramine. The kinetics of reactions of HOI with organic model compounds as well as the resulting CHI3 formation were measured. Substituted phenols, phenol, and, to a smaller extent, α-methyl carbonyl compounds were found to be reactive toward HOI and also to yield CHI3. Resorcinol (m-hydroxyphenol) had the highest yield of CHI3. The kinetics of I-THM formation were also measured in natural waters which were oxidatively treated with ozone, chlorine, or chloramine. When ozone was used, no I-THMs were detected and ≥90% of I- was transformed to IO3-. Chlorine led to the formation of both IO3- and I-THMs. With increasing chlorine doses, the CHI3 formation decreased, whereas IO3- formation, as well as the formation of classical THMs such as chloroform, increased. In chloramination processes, I-THMs (especially CHI3) were the main products. The CHI3 formation in the oxidation of natural waters increased in the order O3 < Cl2 < NH2Cl.
Article
In aqueous oxidative processes with ozone (O3), chlorine, or chloramine, naturally occurring iodide (I-) can easily be oxidized to hypoiodous acid (HOI) which can react with natural organic matter (NOM) or be further oxidized to iodate (IO3-). Such processes can be of importance for the geochemistry of iodine and for the fate of iodine in industrial processes (drinking water treatment, aquacultures). Whereas IO3- is the desired sink for iodine in drinking waters, iodoorganic compounds (especially iodoform, CHI3) are problematic due to their taste and odor. To assess the sink for iodine during oxidation of natural waters, we determined the kinetics of several oxidation reactions of HOI. Ozone, chlorine, and chloramine have been tested as potential oxidants. Ozone oxidized both HOI and hypoiodite (OI-) (kO3+HOI = 3.6 × 104 M-1 s-1; kO3+OI− = 1.6 × 106 M-1 s-1) in a fast reaction. Chlorine species oxidized HOI by a combination of second- and third-order reactions (k‘ ‘HOCl+HOI = 8.2 M-1 s-1; k‘ ‘‘HOCl+HOI = 8.3 × 104 M-2 s-1; kOCl-+HOI = 52 M-1 s-1). Monochloramine did not further oxidize HOI. The probability of the formation of iodoorganic compounds during drinking water disinfection therefore increases in the order O3 < Cl2 < NH2Cl. In aquacultures, I- is transformed to IO3- within seconds to minutes in the presence of chlorine or ozone. In the surface boundary layer of seawater, O3 oxidizes I- to HOI but not to IO3-.
Article
Bromate (BrO(3)(-)) in drinking water is traditionally seen as an ozonation byproduct from the oxidation of bromide (Br(-)), and its formation during chlorination is usually not significant. This study shows enhanced bromate formation during chlorination of bromide-containing waters in the presence of cupric oxide (CuO). CuO was effective to catalyze hypochlorous acid (HOCl) or hypobromous acid (HOBr) decay (e.g., at least 10(4) times enhancement for HOBr at pH 8.6 by 0.2 g L(-1) CuO). Significant halate concentrations were formed from a CuO-catalyzed hypohalite disproportionation pathway. For example, the chlorate concentration was 2.7 ± 0.2 μM (225.5 ± 16.7 μg L(-1)) after 90 min for HOCl (C(o) = 37 μM, 2.6 mg L(-1) Cl(2)) in the presence of 0.2 g L(-1) CuO at pH 7.6, and the bromate concentration was 6.6 ± 0.5 μM (844.8 ± 64 μg L(-1)) after 180 min for HOBr (C(o) = 35 μM) in the presence of 0.2 g L(-1) CuO at pH 8.6. The maximum halate formation was at pHs 7.6 and 8.6 for HOCl or HOBr, respectively, which are close to their corresponding pK(a) values. In a HOCl-Br(-)-CuO system, BrO(3)(-) formation increases with increasing CuO doses and initial HOCl and Br(-) concentrations. A molar conversion (Br(-) to BrO(3)(-)) of up to (90 ± 1)% could be achieved in the HOCl-Br(-)-CuO system because of recycling of Br(-) to HOBr by HOCl, whereas the maximum BrO(3)(-) yield in HOBr-CuO is only 26%. Bromate formation is initiated by the formation of a complex between CuO and HOBr/OBr(-), which then reacts with HOBr to generate bromite. Bromite is further oxidized to BrO(3)(-) by a second CuO-catalyzed process. These novel findings may have implications for bromate formation during chlorination of bromide-containing drinking waters in copper pipes.
Article
In order to more effectively use iodine isotope ratios, 129 I/ 127 I, as hydrological and geochemical tracers in aquatic systems, a new high performance liquid chromatography (HPLC) method was developed for the determination of iodine speciation. The dissolved iodine species that dominate natural water systems are iodide, iodate, and organic iodine. Using this new method, iodide was determined directly by combining anion exchange chromatography and spectrophotometry. Iodate and the total of organic iodine species are determined as iodide, with minimal sample preparation, compared to existing methods. The method has been applied to quantitatively determine iodide, iodate as the difference of total inorganic iodide and iodide after reduction of the sample by NaHSO 3 , and organic iodine as the difference of total iodide (after organic decomposition by dehydrohalogenation and reduction by NaHSO 3) and total inorganic iodide. Analytical accuracy was tested: (1) against certified reference material, SRM 1549, powdered milk (NIST); (2) through the method of standard additions; and (3) by comparison to values of environmental waters measured independently by inductively coupled plasma mass spectrometry (ICP-MS). The method has been successfully applied to measure the concentrations of iodide species in rain, surface and ground water, estuarine and seawater samples. The detection limit was ∼1 nM (0.2 ppb), with less than 3% relative standard deviation (R.S.D.) for samples determined by standard additions to an iodide solution of 20 nM in 0.1 M NaCl. This technique is one of the few methods sensitive enough to accurately quantify stable iodine species at nanomolar concentrations in aquatic systems across a range of matrices, and to quantitatively measure organic iodine. Additionally, this method makes use of a very dilute mobile phase, and may be applied to small sample volumes without pre-column concentration or post-column reactions.
Article
Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of the 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. A review of current literature shows that all values necessary for reproducible, quantitative chemical state analysis are usually not provided. This paper reports a more consistent, practical and effective approach to curve-fitting the various chemical states in a variety of Sc, Ti, V, Cu and Zn metals, oxides and hydroxides. The curve-fitting procedures proposed are based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of the literature references, and (3) specific literature references where fitting procedures are available. Binding energies, full-width at half maximum (FWHM) values, spin-orbit splitting values, asymmetric peak-shape fitting parameters, and, for Cu and Zn, Auger parameters values are presented. The quantification procedure for Cu species details the use of the shake-up satellites for Cu(II)-containing compounds and the exact binding energies of the Cu(0) and Cu(I) peaks. The use of the modified Auger parameter for Cu and Zn species allows for corroborating evidence when there is uncertainty in the binding energy assignment. These procedures can remove uncertainties in analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.
Article
Analytical data by ICP-MS measurements after pyrohydrolysis on a reasonably large series of samples representing about 300 rocks of major units and subunits of the earth's crust, and a few organic materials, are provided for a genetic discussion. Biogenic accumulation and volatilization of iodine from metamorphosed sediments and magmatic rocks has caused extreme gradients of concentrations towards the top of the oceanic and continental crust. Transporting agents for recycling into surface water were hydrothermal fluids and partial volatilization from surface waters which occurred as methyl iodide. Because of the low iodine concentrations in magmatic and metamorphic rocks such samples exposed at the earth's surface not far from the seashore could have undergone contamination by iodine which escaped from the oceans. The high average concentrations of 30 ppm I in deep-sea carbonates and of 2.5 ppm I in continental limestones were accumulated by planktonic and shallow sea organisms, respectively. Deep-sea clays (3.9 ppm I) and continental shales (1.8 ppm I) contain the residual iodine after dissolution and oxidation of a major fraction of carbonates and organic carbon, respectively. Shales vary more in iodine than deep-sea clays because of greater variations in the environments of deposition and diagenesis. The I/C weight ratio increases from 10−3 to 2×10−1 from reduced to oxygenated recent nearshore sediments. Iodine is more stable than carbon during diagenesis of biogenic sediments. Greywackes and sandstones contain on average 150 and 120 ppb I, respectively. Metasedimentary gneisses, mica schists and granulites have as little as 12 to 25 ppb I and have lost from 75 to >95% of their iodine at metamorphic temperatures. Granites, granodiorites, tonalites and basalts are even lower in iodine and contain 4 to 9 ppb I almost independent of the species of magmatic rock. The continental crust, the oceanic crust (including seawater) and bulk Earth's crust contain 119 ppb, 777 ppb and ∼300 ppb I, respectively. Nearly 70% of I is calculated to exist in ocean sediments. The Cl/I weight ratios of the continental, oceanic and bulk Earth's crust are 3800, 4500 and 4300, respectively, to be compared with 1210 and 403 in the Orgueil and Ivuna Cl chondrites.
Article
A new ion chromatographic method has been developed for the simultaneous analysis of the major matrix anions (chloride, nitrate, phosphate, sulfate, etc.), lower concentrated bromide, oxyhalides (iodate, chlorite, bromate) and nitrite in fresh waters and sea water. The method is based on an anion exchange chromatographic separation followed by a sequential analysis through conductivity and subsequent postcolumn reaction with UV detection. Whereas the matrix anions are quantified by conductivity, the oxyhalides and nitrite are measured by the oxidation product I3− which they generate from iodide in the postcolumn reaction. The detection limits as determined for bromide, bromate and nitrite are 3, 0.1 and 0.5 μg l−1, respectively.
Article
The objective of this study was to evaluate the formation and speciation of iodinated trihalomethanes (I-THMs) from preformed chloramination of waters containing bromide (Br(-)) and iodide (I(-)) at a Br(-)/I(-) weight ratio of 10:1. The factors investigated were pH, iodide to dissolved organic carbon (I(-)/DOC) ratio, and NOM characteristics, specifically SUVA(254). A Br(-)/I(-) ratio of 1:2 was also evaluated to determine the importance of Br(-) and I(-) concentrations and ratio on I-THM formation and speciation. Regulated triholamethanes (THMs) were measured alongside I-THMs for a more complete understanding of trihalomethane formation. The results showed that, in general, both I-THM and THM formation increased with decreased pH. Greater formation at lower pH was likely attributed to monochloramine decomposition and the formation of additional oxidants and substituting agents, most notably chlorine. For pH ≥ 7.5, I-THM yield increased with increasing I(-)/DOC ratio and decreasing specific ultraviolet absorbance (SUVA(254)) of the water. The Br(-)/I(-), Br(-)/DOC and I(-)/DOC ratios were important factors for I-THM and THM speciation. At pH 6, dichloroiodomethane (CHCl(2)I) and bromochloroiodomethane (CHBrClI) were the dominant species at the common bromide and iodide levels. For pH ≥ 7.5 and for elevated bromide and iodide levels, iodoform (CHI(3)) was always the dominant specie regardless of the Br(-)/I(-) ratio. The results demonstrated that it is important to examine I-THM formation and speciation at typical Br(-)/I(-) ratios (≈ 10) of natural waters, which have often been overlooked in previous investigations, in order to obtain practical and relevant results.
Article
An increasing number of utilities in the United States have been switching from chlorination to chloramination practices to comply with the more stringent trihalomethane (THM) and haloacetic acid (HAA) regulations. This has important implications for disinfection byproduct (DBP) formation because the reactions of chlorine and monochloramine (NH(2)Cl) with natural organic matter (NOM) are not the same. In this study, iodinated trihalomethane (I-THM) formation from preformed NH(2)Cl and prechlorination (at two chlorine doses and contact times) followed by ammonia addition was compared. A representative bromide/iodide ratio of 10:1 was selected and four bromide/iodide levels (ambient, 50/5 or 100/10, 200/20, and 800/80 [μg/L/μg/L]) were evaluated. The results showed that I-THM formation was generally lower for prechlorination as compared to preformed NH(2)Cl due to the oxidation of iodide to iodate by chlorine. However, while prechlorination minimized iodoform (CHI(3)) formation, prechlorination sometimes formed more I-THMs as compared to preformed NH(2)Cl due to a large increase in the formation of brominated I-THM species, which were formed at much smaller amounts from preformed NH(2)Cl. I-THM concentrations and speciation for the two chloramination scenarios (i.e., preformed NH(2)Cl vs prechlorination followed by ammonia) depended on chlorine dose, contact time, bromide/iodide concentration, and NOM characteristics of the source water (SUVA(254)).
Article
Iodide and iodate can be determined by two new methods using anion-exchange chromatography with postcolumn reaction and UV/visible detection. Iodide is determined as IBr(2)(-) at 249 nm. Iodate is determined as I(3)(-) at 288 nm. The analyses can be run completely automatically and do not require any sample pretreatment. The detection limits for iodide and iodate are 0.1 μg/L. The methods have been successfully applied to determine iodide and iodate in several mineral waters and in drinking water as well as for the determination of iodide in table salt.
Article
Iodinated disinfection byproducts (DBPs) are generally more toxic than their chlorinated and brominated analogues. Up to date, only a few iodinated DBPs in drinking water have been identified by gas chromatography/mass spectrometry. In this work, a method for fast selective detection of polar iodinated DBPs was developed using an electrospray ionization-triple quadrupole mass spectrometer (ESI-tqMS) by conducting precursor ion scan of iodide at m/z 126.9. With such a method, pictures of polar iodinated DBPs in chlorinated, chloraminated, and chlorine-ammonia treated water samples were achieved. By coupling state-of-the-art ultra performance liquid chromatography (UPLC) to the ESI-tqMS, structures of 17 iodinated DBPs were tentatively proposed. The results fully demonstrate that, with respect to the DBP number/levels among the three disinfection processes, chloramination generally generated the most/highest iodinated DBPs, chlorination generally produced the fewest/lowest iodinated DBPs, and chlorine-ammonia sequential treatment formed iodinated DBPs lying in between; the numbers of iodinated DBPs in chloraminated Suwannee River Fulvic Acid (SRFA) and Humic Acid (SRHA) were nearly the same, but the levels of aliphatic iodinated DBPs were higher in the chloraminated SRFA while the levels of aromatic iodinated DBPs were higher in the chloraminated SRHA; a couple of nitrogenous iodinated DBPs were found in chloramination and chlorine-ammonia treatment. The ratio of total organic iodine levels in chlorine-ammonia sequential treatment and chloramination could be expressed as a function of the lag time of ammonia addition.
Article
An occurrence study was conducted to measure five iodo-acids (iodoacetic acid, bromoiodoacetic acid, (Z)-3-bromo-3-iodo-propenoic acid, (E)-3-bromo-3-iodo-propenoic acid, and (E)-2-iodo-3-methylbutenedioic acid) and two iodo-trihalomethanes (iodo-THMs), (dichloroiodomethane and bromochloroiodomethane) in chloraminated and chlorinated drinking waters from 23 cities in the United States and Canada. Since iodoacetic acid was previouslyfound to be genotoxic in mammalian cells, the iodo-acids and iodo-THMs were analyzed for toxicity. A gas chromatography (GC)/negative chemical ionization-mass spectrometry (MS) method was developed to measure the iodo-acids; iodo-THMs were measured using GC/high resolution electron ionization-MS with isotope dilution. The iodo-acids and iodo-THMs were found in waters from most plants, at maximum levels of 1.7 microg/L (iodoacetic acid), 1.4 microg/L (bromoiodoacetic acid), 0.50 microg/L ((Z)-3-bromo-3-iodopropenoic acid), 0.28 microg/L ((E)-3-bromo-3-iodopropenoic acid), 0.58 microg/L ((E)-2-iodo-3-methylbutenedioic acid), 10.2 microg/L (bromochloroiodomethane), and 7.9 microg/L (dichloroiodomethane). Iodo-acids and iodo-THMs were highest at plants with short free chlorine contact times (< 1 min), and were lowest at a chlorine-only plant or at plants with long free chlorine contact times (> 45 min). Iodide levels in source waters ranged from 0.4 to 104.2 microg/L (when detected), but there was not a consistent correlation between bromide and iodide. The rank order for mammalian cell chronic cytotoxicity of the compounds measured in this study, plus other iodinated compounds, was iodoacetic acid > (E)-3-bromo-2-iodopropenoic acid > iodoform > (E)-3-bromo-3-iodo-propenoic acid > (Z)-3-bromo-3-iodo-propenoic acid > diiodoacetic acid > bromoiodoacetic acid > (E)-2-iodo-3-methylbutenedioic acid > bromodiiodomethane > dibromoiodomethane > bromochloroiodomethane approximately chlorodiiodomethane > dichloroiodomethane. With the exception of iodoform, the iodo-THMs were much less cytotoxic than the iodo-acids. Of the 13 compounds analyzed, 7 were genotoxic; their rank order was iodoacetic acid > diiodoacetic acid > chlorodiiodomethane > bromoiodoacetic acid > E-2-iodo-3-methylbutenedioic acid > (E)-3-bromo-3-iodo-propenoic acid > (E)-3-bromo-2-iodopropenoic acid. In general, compounds that contain an iodo-group have enhanced mammalian cell cytotoxicity and genotoxicity as compared to their brominated and chlorinated analogues.
Article
Iodoacid drinking water disinfection byproducts (DBPs) were recently uncovered in drinking water samples from source water with a high bromide/iodide concentration that was disinfected with chloramines. The purpose of this paper is to report the analytical chemical identification of iodoacetic acid (IA) and other iodoacids in drinking water samples, to address the cytotoxicity and genotoxicity of IA in Salmonella typhimurium and mammalian cells, and to report a structure-function analysis of IA with its chlorinated and brominated monohalogenated analogues. The iodoacid DBPs were identified as iodoacetic acid, bromoiodoacetic acid, (Z)- and (E)-3-bromo-3-iodopropenoic acid, and (E)-2-iodo-3-methylbutenedioic acid. IA represents a new class (iodoacid DBPs) of highly toxic drinking water contaminants. The cytotoxicity of IA in S. typhimurium was 2.9x and 53.5x higher than bromoacetic acid (BA) and chloroacetic acid (CA), respectively. A similar trend was found with cytotoxicity in Chinese hamster ovary (CHO) cells; IA was 3.2x and 287.5x more potent than BA and CA, respectively. This rank order was also expressed in its genotoxicity with IA being 2.6x and 523.3x more mutagenic in S. typhimurium strain TA100 than BA and CA, respectively. IA was 2.0x more genotoxic than BA and 47.2x more genotoxic than CA in CHO cells. The rank order of the toxicity of these monohalogenated acetic acids is correlated with the electrophilic reactivity of the DBPs. IA is the most toxic and genotoxic DBP in mammalian cells reported in the literature. These data suggest that chloraminated drinking waters that have high bromide and iodide source waters may contain these iodoacids and most likely other iodo-DBPs. Ultimately, it will be important to know the levels at which these iodoacids occur in drinking water in order to assess the potential for adverse environmental and human health risks.
Article
Two natural waters were fortified with various levels of bromide or iodide ions (0-30 microM) and chlorinated in the laboratory to study the impact of bromide and iodide ions on the formation and speciation of disinfection byproducts. Trihalomethanes (THMs), haloacetic acids (HAAs), total organic halogen (TOX), and its halogen-specific fractions total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI), were measured in this work. The molar yields of THMs and HAAs increased as the initial bromide concentration increased. No significant change in TOX concentration was found for varying bromide concentrations. However, TOX concentrations decreased substantially with increasing initial iodide concentrations. At higher levels of bromide, there was a decreasing level of unknown TOX and unknown TOCl but an increasing level of unknown TOBr. The extent of iodine substitution was much lower than that of bromine substitution when comparing identical initial concentrations because a substantial amount of iodide was oxidized to iodate by chlorine. The tendency toward iodate formation resulted in the unusual situation where higher chlorine doses actually caused reduced levels of iodinated organic byproducts. Quantitative assessment of the results of this study showed a good agreement with kinetic data in the literature.
The corrosion behaviour of copper in neutral tap water. Part I: Corrosion mechanisms Copper corrosion in potable water distribution systems: Influence of copper products on the corrosion behavior
  • Y Feng
  • W K Teo
  • K S Siow
  • K Tan
  • A K Hsieh
  • J J Shim
  • J G Kim
Feng, Y.; Teo, W. K.; Siow, K. S.; Tan, K. l.; Hsieh, A. K. The corrosion behaviour of copper in neutral tap water. Part I: Corrosion mechanisms. Corros. Sci. 1996, 38 (3), 369−385. Environmental Science & Technology Article dx.doi.org/10.1021/es5032079 | Environ. Sci. Technol. XXXX, XXX, XXX−XXX G (25) Shim, J. J.; Kim, J. G. Copper corrosion in potable water distribution systems: Influence of copper products on the corrosion behavior. Mater. Lett. 2004, 58, 2002−2006.
Sources of iodine and iodine 129 in rivers 1149. (5) Muramatsu, Y.; Hans Wedepohl, K. The distribution of iodine in the earth's crust
  • J E Moran
  • S D Oktay
  • P H Santschi
Moran, J. E.; Oktay, S. D.; Santschi, P. H. Sources of iodine and iodine 129 in rivers. Water Resour Res. 2002, 38 (8), 1149. (5) Muramatsu, Y.; Hans Wedepohl, K. The distribution of iodine in the earth's crust. Chem. Geol. 1998, 147 (3−4), 201−216. (6) Tsunogai, S.; Henmi, T. Iodine in the surface water of the ocean.
Occurrence and mammalian cell toxicity of iodinated disinfection byproducts in drinking water 8330−8338. (8) Bichsel, Y.; von Gunten, U. Oxidation of iodide and hypoiodous acid in the disinfection of natural waters
  • G W Luther
  • A B Mckague
  • R J Miltner
  • E D Wagner
  • M J Plewa
  • J C Nagy
  • K Kumar
Luther, G. W.; McKague, A. B.; Miltner, R. J.; Wagner, E. D.; Plewa, M. J. Occurrence and mammalian cell toxicity of iodinated disinfection byproducts in drinking water. Environ. Sci. Technol. 2008, 42 (22), 8330−8338. (8) Bichsel, Y.; von Gunten, U. Oxidation of iodide and hypoiodous acid in the disinfection of natural waters. Environ. Sci. Technol. 1999, 33 (22), 4040−4045. (9) Nagy, J. C.; Kumar, K.; Margerum, D. W. Non-Metal redox kinetics -oxidation of iodide by hypochlorous acid and by nitrogen trichloride measured by the pulsed-accelerated-flow method. Inorg.
  • J Oceanogr
  • Soc
  • S D Jpn Richardson
  • F Fasano
  • Ellington
J. Oceanogr. Soc. Jpn. 1971, 27 (2), 67−72. (7) Richardson, S. D.; Fasano, F.; Ellington, J. J.; Crumley, F. G.;
European Communities (Drinking water) (No.2) Regulations;Brussels
  • European Communities
European Communities. European Communities (Drinking water) (No.2) Regulations;
Environmental Protection Agency. National Primary Drinking Water Regulations
  • Brussels
Brussels, 2007. (16) U.S. Environmental Protection Agency. National Primary Drinking Water Regulations;