Article

Investigation of the mechanism of chlorination of glyphosate and glycine in water

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Abstract

The chlorination reactions of glyphosate and glycine in water were thoroughly studied. Utilizing isotopically enriched (13C and 15N) samples of glycine and glyphosate and 1H, 13C, 31P, and 15N NMR spectroscopy we were able to identify all significant terminal chlorination products of glycine and glyphosate, and show that glyphosate degradation closely parallels that of glycine. We have determined that the C1 carboxylic acid carbon of glycine/glyphosate is quantitatively converted to CO2 upon chlorination. The C2 methylene carbon of glycine/glyphosate is converted to CO2 and methanediol. The relative abundance of these two products is a function of the pH of the chlorination reactions. Under near neutral to basic reaction conditions (pH 6-9), CO2 is the predominant product, whereas, under acidic reaction conditions (pH < 6) the formation of methanediol is favored. The C3 phosphonomethylene carbon of glyphosate is quantitatively converted to methanediol under all conditions tested. The nitrogen atom of glycine/glyphosate is transformed into nitrogen gas and nitrate, and the phosphorus moiety of glyphosate produces phosphoric acid upon chlorination. In addition to these terminal chlorination products, a number of labile intermediates were also identified including N-chloromethanimine, N-chloroaminomethanol, and cyanogen chloride. The chlorination products identified in this study are not unique to glyphosate and are similar to those expected from chlorination of amino acids, proteins, peptides, and many other natural organic matters present in drinking water.

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... Glyphosate decay was complete at chlorine/glyphosate molar ratios close to 2 or higher. Consistent with the previous work (Mehrsheikh et al., 2005), we determined that the phosphonic acid moiety of glyphosate is converted into phosphoric acid at all ratio of applied chlorine. The mass balance for phosphorus confirms the NMR results that the phosphorus of glyphosate is quantitatively transformed into phosphoric acid. ...
... Cyanogen chloride (V; CNCl)) was reported as a transitory product of glyphosate chlorination by NMR spectroscopy (Mehrsheikh et al., 2005). We also found evidence for the formation of cyanogen chloride(V) by detecting its hydrolysis product, cyanate(VI; CNO À ), using IonPac HPLC analysis. ...
... However, at a chlorine/glyphosate molar ratio of 5, its concentration decreased substantially and no cyanogen chloride/ cyanate was detected at chlorine/glyphosate molar ratios of 10 or higher. This is consistent with the results obtained from the NMR experiment reported by Mehrsheikh et al. (2005) which showed ready decomposition of cyanogen chloride (V) to carbon dioxide in the presence of excess chlorine. The comparison of the products of glyphosate chlorination conducted at pH ¼ 7 and 8 shows no significant differences within the pH range relevant to the purification of natural water commonly sourced for drinking water (data not shown). ...
Article
Chlorination reactions of glyphosate, glycine, and sodium cyanate were conducted in well-agitated reactors to generate experimental kinetic measurements for the simulation of chlorination kinetics under the conditions of industrial water purification plants. The contribution of different by-products to the overall degradation of glyphosate during chlorination has been identified. The kinetic rate constants for the chlorination of glyphosate and its main degradation products were either obtained by calculation according to experimental data or taken from published literature. The fit of the kinetic constants with experimental data allowed us to predict consistently the concentration of the majority of the transitory and terminal chlorination products identified in the course of the glyphosate chlorination process. The simulation results conducted at varying aqueous chlorine/glyphosate molar ratios have shown that glyphosate is expected to degrade in fraction of a second under industrial aqueous chlorination conditions. Glyphosate chlorination products are not stable under the conditions of drinking water chlorination and are degraded to small molecules common to the degradation of amino acids and other naturally occurring substances in raw water. The kinetic studies of the chlorination reaction of glyphosate, together with calculations based on kinetic modeling in conditions close to those at real water treatment plants, confirm the reaction mechanism that we have previously suggested for glyphosate chlorination.
... Formation of N-chloroglycine as the product of the reaction between glycine and FAC is known and has been investigated thoroughly [16][17][18]. Despite the different species of glycine (pKa1 = 2.35, pKa2 = 9.78) and HOCl (pK a = 7.4) [19] present in aqueous solution (cf. ...
... N-Chloroglycine was produced by mixing the FAC solution with glycine. To avoid the formation of N,N-dichloroglycine, FAC to glycine ratio was 0.1 [18]. The concentration of Nchloroglycine in the stock solution was confirmed by UV measurements (optical path length 10 cm, pH ≥ 4, ε Nchloroglycine at 254 nm = 375 M −1 cm −1 [26]). ...
... However, the concentration of free amino acids in raw water is reported to be around 2.5 μg L −1 at highest with a maximum of 20% glycine content. Moreover, compared with FAC, glycine concentration is way lower, and in excess of FAC, N,N-dichloroglycine will form [18,40,41]. N,N-Dichloroglycine is subject to fast auto-decomposition (t 1/2 = 13.0 min) [42]. All in all, it is implausible that background glycine concentration will cause any interferences due to low abundance and further degradation of N,N-dichloroglycine. ...
Article
Full-text available
Free available chlorine (FAC) is the most widely used chemical for disinfection and in secondary disinfection; a minimum chlorine residual must be present in the distribution system. FAC can also be formed as an impurity in ClO2 production as well as a secondary oxidant in the ClO2 application, which has to be monitored. In this study, a new method is developed based on the reaction of FAC with glycine in which the amine group selectively scavenges FAC and the N-chloroglycine formed can be measured by ion chromatography with conductivity detector (IC-CD). Utilizing IC for N-chloroglycine measurement allows this method to be incorporated into routine monitoring of drinking water anions. For improving the sensitivity, IC was coupled with post-column reaction and UV detection (IC-PCR-UV), which was based on iodide oxidation by N-chloroglycine resulting in triiodide. The method performance was quantified by comparison of the results with the N,N-diethyl-p-phenylenediamine (DPD) method due to the unavailability of an N-chloroglycine standard. The N-chloroglycine method showed limits of quantification (LOQ) of 24 μg L−1 Cl2 and 13 μg L−1 Cl2 for IC-CD and IC-PCR-UV, respectively. These values were lower than those of DPD achieved in this research and in ultrapure water. Measurement of FAC in the drinking water matrix showed comparable robustness and sensitivity with statistically equivalent concentration that translated to recoveries of 102% for IC-CD and 105% for IC-PCR-UV. Repeatability and reproducibility performance were enhanced in the order of DPD, IC-CD, and IC-PCR-UV. Measurement of intrinsic FAC in the ClO2 application revealed that the N-chloroglycine method performed considerably better in such a system where different oxidant species (ClO2, FAC, chlorite, etc.) were present.
... Experimentally determined correlation slope follows the order of colchicine > aldicarb > glyphosate (Table 2). Previous studies Mehrsheikh et al., 2006;Ray et al., 1981;Arnstein et al., 1949;Mason et al., 1990;and Miles, 1991) described chlorination pathways and molecular structure changes that are consistent with the sensor measurements and kinetic analysis results. In chlorinated water, aldicarb is oxidized to yield aldicarb-sulphoxide and aldicarb-sulphone with a half-life t 1/2 * < 1 min (Miles, 1991;Mason et al., 1990) leading to the rapidly established steady-state chlorine loss (Yang et al., 2007). ...
... On the other hand, glyphosate follows more complex oxidation pathways resulting in differential responses between total and free chlorines. Brosillon et al. (2006) and Mehrsheikh et al. (2006) demonstrated in experiments that the carbamate compound is oxidized to form monochloroglycine and then dichloroglycine, followed by the rate-limiting dichloroglycine decomposition to form chloraldimine and hydrochloric acid (t 1/2 * ¼ 3.04 min), in which cyanogen chloride oxidation produces chloramines and cyanate (NCO À ) in three-branched reactions. Based on second-order reaction constants reported in Brosillon et al. (2006), calculations indicate that !40% reactions produce chloramines as the final products, which would not be registered in the sensor as total chlorine loss. ...
Article
Accurate detection and identification of natural or intentional contamination events in a drinking water pipe is critical to drinking water supply security and health risk management. To use conventional water quality sensors for the purpose, we have explored a real-time event adaptive detection, identification and warning (READiw) methodology and examined it using pilot-scale pipe flow experiments of 11 chemical and biological contaminants each at three concentration levels. The tested contaminants include pesticide and herbicides (aldicarb, glyphosate and dicamba), alkaloids (nicotine and colchicine), E. coli in terrific broth, biological growth media (nutrient broth, terrific broth, tryptic soy broth), and inorganic chemical compounds (mercuric chloride and potassium ferricyanide). First, through adaptive transformation of the sensor outputs, contaminant signals were enhanced and background noise was reduced in time-series plots leading to detection and identification of all simulated contamination events. The improved sensor detection threshold was 0.1% of the background for pH and oxidation–reduction potential (ORP), 0.9% for free chlorine, 1.6% for total chlorine, and 0.9% for chloride. Second, the relative changes calculated from adaptively transformed residual chlorine measurements were quantitatively related to contaminant-chlorine reactivity in drinking water. We have shown that based on these kinetic and chemical differences, the tested contaminants were distinguishable in forensic discrimination diagrams made of adaptively transformed sensor measurements.
... The reaction mechanism is similar to those previously reported for chlorination of other amino acids. The compound N-chloromethanimine, with a similar structure of R À CH ¼ NCl, was produced from glycine and was reported to convert to another transitory product of chloroaminomethanol (Mehrsheikh et al., 2006) under acidic or neutral reaction conditions. Decarboxylation and elimination of HCl from the labile N-dichloroglycine produced N-chloromethanimine as a transitory product. ...
Article
Unregulated disinfection byproducts (DBPs), including nitrogenous disinfection byproducts (N-DBPs), originating from chlorination of the precursor amino acid phenylalanine in aqueous systems, were identified in laboratory reactions and distributed tap. The major N-DBP identified was phenylacetonitrile, and minor DBPs of benzyl chloride, phenylacetaldehyde, 2-chlorobenzyl cyanide, and 2, 6-diphenylpyridine were also formed. Phenylacetonitrile was generated through decarboxylation, dechlorination and/or hydrolysis processes. With an aromatic structure, phenylacetonitrile has an unpleasant odor of various descriptors and an odor threshold concentration of 0.2 ppt-v as measured through gas chromatography-olfactometry. The half-life of phenylacetonitrile in reagent water and chlorinated water at 19 °C were 121 h and 792 h, respectively. The occurrence of phenylacetonitrile as an N-DBP in tap water was investigated for the first time; the results revealed that μg/L concentrations were present in nine different distributed drinking waters in China and the United States. Phenylacetonitrile deteriorates the aesthetic quality of drinking water and may present risk due to its prolonged existence in drinking water, especially in the presence of residual chlorine.
... 29,30 Previous research found mainly methanediol and only a trace amount of 14 CO 2 upon reaction of 14 C-glyphosate (labelled at the phosphonomethylene position) and sodium hypochlorite. 31 Therefore, good recovery of 14 C was expected when using sodium hypochlorite. Each plant section was placed in a plastic tube (20 mL) containing 0.5 mL of sodium hypochlorite solution (100 g L −1 ). ...
Article
Background Perennial ryegrass (Lolium perenne) has developed resistance to glyphosate within New Zealand vineyards following many years of herbicide application. The objectives of this work were to confirm resistance within two populations obtained from affected vineyards and to determine the mechanism of resistance to glyphosate.ResultsPopulation O was confirmed to have a 25-fold resistance to glyphosate whereas Population J had a 7-fold resistance. Results of genotyping assays demonstrated a single nucleotide substitution at Codon 106 of EPSPS in Population O but not Population J. Glyphosate resistant and susceptible populations did not differ in glyphosate absorption. However, in both resistant populations, much more of the absorbed 14C-glyphosate remained in the treated leaf than occurred in the susceptible population. Significantly more glyphosate was found in the pseudostem region of susceptible plants than resistant plants.Conclusion Both target site and non-target site mechanisms of glyphosate resistance were found in the perennial ryegrass population with 25-fold resistance, whereas only the non-target site mechanism of resistance was found in the population with 7-fold resistance. This is first study of the mechanism of glyphosate resistance in perennial ryegrass.
... Pesticide DBPs have included oxidation products of S-triazine herbicides (prometryne, terbutryne, ametryne, and desmetryne) when reacted with chlorine or chlorine dioxide [242]; chlorinated and non-chlorinated by-products of the herbicide isoproturon when reacted with chlorine or chlorine dioxide [243]; chlorinated byproducts of the herbicide chlortoluron when reacted with chlorine [244]; an oxidation product of isoxaflutole (under chlorination conditions) [245]; an oxidation product of chlorpyrifos (chloropyrifos oxon, which is more toxic than the parent pesticide) when treated with chlorine [246]; oxidation products of clethodim when reacted with chlorine [247]; by-products of chloroacetamide herbicides (acetochlor, alachlor, metolachlor, and dimetheamide) when reacted with either ozone or chlorine under simulated drinking-water conditions [248]; by-products of diazinon during UV and UV/ hydrogen peroxide treatment [249]; and an oxidation product (methanediol) from glyphosate [250]. ...
Article
The chemical by-products of chlorine treatment of food and drinking water are compared to those of alternative disinfectants chlorine dioxide, ozone, and chloramine.
... Moreover, it is one of the only disinfectants to have retentive power. But as an oxidizing disinfectant, chlorine can also react with pesticides Mascolo et al., 2001;Brosillon et al., 2006;Mehrsheikh et al., 2006) or natural organic matter (NOM) present in drinking water (Urbansky and Magnuson, 2002) even if the dissolved organic carbon of the water is low (5 mg L À1 ). The organic compounds composing NOM (humic and fulvic acid, polysaccharides, amino sugars and amino acids, proteins, and polyhydroxyaromatic compounds) can produce undesirable disinfection by-products. ...
Article
Previous studies have established that odorous and stable chloraldimines are formed during amino acid chlorination in drinking water treatment. In order to identify at low level (10(-8) M) the presence of these odorous disinfection by-products in drinking water matrixes an analytical method was developed by using head space apparatus (HS) combined with a sorbent trap system linked to a GC with a mass spectrometer detector (HS/Trap/GC/MS). The analyses were carried out in three different drinking water supplies from the Paris area, during the four seasons. Free amino acids were monitored at the inlet of the plant. The odorous disinfection by-products were analyzed at the outlet of each drinking water treatment plant and the different distribution networks were connected to the corresponding plant. The results confirmed that the odorous chloraldimines are produced during chlorination of free amino acids in three different matrixes in different seasons throughout the year (N-chloroisobutaldimine; N-chloromethyl-2-butaldimine; N-chloromethyl-3-butaldimine (6-10 nM). The analytical method (HS/Trap/GC/MS) used to monitor odorous disinfection by-products appeared to be adapted for the detection of these by-products at nM level.
... A proposed mechanism for the formation of CNCl and CNCHCl2 from the chlorination of L-histidine (I) is illustrated in Scheme 2. As with other R-amino acids (22,28), an initial chlorine substitution step is followed by dechlorination and decarboxylation to yield a nitrile (II). It is hypothesized that the two electron-withdrawing groups, sCtN and a heterocycle, will promote electrophilic attack of OClon the -carbon of the intermediate (II). ...
Article
Clinical studies have documented the promotion of respiratory ailments (e.g., asthma) among swimmers, especially in indoor swimming pools. Most studies of this behavior have identified trichloramine (NCl3) as the causative agent for these respiratory ailments; however, the analytical methods employed in these studies were not suited for identification or quantification of other volatile disinfection byproducts (DPBs) that could also contribute to this process. To address this issue, volatile DBP formation resulting from the chlorination of four model compounds (creatinine, urea, L-histidine, and L-arginine) was investigated over a range of chlorine/precursor (Cl/P) molar ratios. Trichloramine was observed to result from chlorination of all four model organic-nitrogen compounds. In addition to trichloramine, dichloromethylamine (CH3NCl2) was detected in the chlorination of creatinine, while cyanogen chloride (CNCl) and dichoroacetonitrile (CNCHCl2) were identified in the chlorination of L-histidine. Roughly 0.1 mg/L (as Cl2) NCl3, 0.01 mg/L CNCHCl2, and 0.01 mg/L CH3NCl2 were also observed in actual swimming pool water samples. DPD/FAS titration and MIMS (membrane introduction mass spectrometry) were both employed to measure residual chlorine and DBPs. The combined application of these methods allowed for identification of sources of interference in the conventional method (DPD/FAS), as well as structural information about the volatile DBPs that formed. The analysis by MIMS clearly indicates that volatile DBP formation in swimming pools is not limited to inorganic chloramines and haloforms. Additional experimentation allowed for the identification of possible reaction pathways to describe the formation of these DBPs from the precursor compounds used in this study.
... By applying these assumptions and the kinetic principle that the rates of adsorption and desorption from the surface are equal, the Langmuir model relates the coverage of molecules on a solid surface to the concentration of the medium above the solid surface at a fixed temperature. 34 It can be represented by the equation (7) where q e (mg/g) is the amount of PMG adsorbed per unit mass of MT particles at equilibrium, C e (mg/L) is the equilibrium liquid-phase concentration of PMG, b is the equilibrium constant (L/mg), and q m is the amount of adsorbate required to form a monolayer (mg/g). The Langmuir constants q m and b at temperatures from 298 to 318 K are reported in Table 2. ...
... Chlorination products of glyphosate, one of the most widely used herbicide in the world, and glycine, one of the intermediates in glyphosate chlorination, were investigated by Mehrsheikh et al. [111]. Both compounds followed a similar degradation route, with the final glyphosate chlorination products identified as methanediol and other small molecules, such as phosphoric acid, nitrate, CO 2 , and N 2 . ...
... As has been shown previously, AMPA is glyphosate's main biodegradation and photodegradation product in the environment, and this is also true for chemical oxidation Mehrsheikh et al., 2006). Simple UV disinfection does not remove AMPA from drinking water Assalin et al., 2010;Klinger et al., 1998). ...
Article
The widely occurring degradation product aminomethylphosphonic acid (AMPA) is a result of glyphosate and amino-polyphosphonate degradation. Massive use of the parent compounds leads to the ubiquity of AMPA in the environment, and particularly in water. The purpose of this review is to summarize and discuss current insights into AMPA formation, transport, persistence and toxicity. In agricultural soils, AMPA is concentrated in the topsoil, and degrades slowly in most soils. It can reach shallow groundwater, but rarely managed to enter deep groundwater. AMPA is strongly adsorbed to soil particles and moves with the particles towards the stream in rainfall runoff. In urban areas, AMPA comes from phosphonates and glyphosate in wastewater. It is commonly found at the outlets of Wastewater Treatment Plants (WWTP). Sediments tend to accumulate AMPA, where it may be biodegraded. Airborne AMPA is not negligible, but does wash-out with heavy rainfall. AMPA is reported to be persistent and can be biologically degraded in soils and sediments. Limited photodegradation in waters exists. AMPA mainly has its sources in agricultural leachates, and urban wastewater effluents. The domestic contribution to urban loads is negligible. There is a critical lack of epidemiological data - especially on water exposure - to understand the toxicological effects, if any, of AMPA on humans. Fortunately, well operated water treatment plants remove a significant proportion of the AMPA from water, even though there are not sufficient regulatory limits for metabolites.
... 6,7 Glyphosate has been classied as probably carcinogenic to humans (group 2A) by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) because there is convincing evidence that it can cause cancer in laboratory animals. 8 Various processes were developed to treat the glyphosatecontaining effluents including advanced oxidation, 9,10 chlorination, 11 ltration, 12 biodegradation 13,14 and adsorption. [15][16][17] Among these, adsorption is still the most versatile and widely used method as it can remove various types of pollutants. ...
Article
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The double valent composite resin (DR) was prepared within nano-sized Fe(II) and Fe(III) hydroxyl oxide crosslinking polystyrene anion exchanger resin for efficient glyphosate removal from water. The structure, morphology, Fe species, crystal phase, and elemental composition of the prepared DR composites were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of contact time, pH, temperature, coexisting anions and regeneration were studied in batch mode. It was found that a low pH value favors the adsorption of glyphosate, and the adsorption kinetics were well fitted by a pseudo-second-order model. The exhausted DR composites could be regenerated by NaOH solution for repeated use without any significant capacity loss, where the adsorbed glyphosate was effectively desorbed into the solution. Fixed-bed adsorption further validated that DR composites would be of considerable potential in the removal of glyphosate from contaminated waters.
... Pesticide DBPs have included oxidation products of S-triazine herbicides (prometryne, terbutryne, ametryne, and desmetryne) when reacted with chlorine or chlorine dioxide [242]; chlorinated and non-chlorinated by-products of the herbicide isoproturon when reacted with chlorine or chlorine dioxide [243]; chlorinated byproducts of the herbicide chlortoluron when reacted with chlorine [244]; an oxidation product of isoxaflutole (under chlorination conditions) [245]; an oxidation product of chlorpyrifos (chloropyrifos oxon, which is more toxic than the parent pesticide) when treated with chlorine [246]; oxidation products of clethodim when reacted with chlorine [247]; by-products of chloroacetamide herbicides (acetochlor, alachlor, metolachlor, and dimetheamide) when reacted with either ozone or chlorine under simulated drinking-water conditions [248]; by-products of diazinon during UV and UV/ hydrogen peroxide treatment [249]; and an oxidation product (methanediol) from glyphosate [250]. ...
Article
Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-mug/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for approximately 60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.
... To assess interferences from organic chloramines on our MSC system, glycine was selected as a model organic amino compound. This latter one was indeed already demonstrated to be chlorine-reactive forming organic chloramines (N-chloro or N-dichloroglycine) [27]. ...
Article
Inorganic chloramines are disinfection by-products resulting from the unwanted reaction between chlorine used as disinfectant in swimming pools and nitrogenous compounds brought by bathers. This parameter (total chloramines or combined chlorine) is currently measured on site by a colorimetric method that does not allow to measure only inorganic chloramines. In this paper, a multi-syringe chromatography system combined with a post column derivatization is applied for the first time for the specific detection of the three individual inorganic chloramines (monochloramine, dichloramine and trichloramine). These latter ones are separated using a low-pressure monolithic C18 column, and separately detected after a post-column reaction with the chromogenic reagent ABTS (2,2'-azino-bis-(3-ethyl-benzothiazoline)-6-sulfonic acid-diammonium salt). Development of two ABTS reagents provides discrimination of chlorine and monochloramine that are not separated on the column. Optimization of the experimental conditions enables determination of inorganic chloramines with very good detection limits (around 10 μg eq.Cl2 L-1) without interferences from other chlorinated compounds such as organic chloramines or free available chlorine. The validation of the whole procedure has been successfully applied to real swimming pools samples.
... DBPs formation mechanisms are strongly influenced by operational parameters such as: type of disinfectant used, dose and contact time, and by the physico-chemical features of raw water (pH, temperature, NOM, ammonium, metals) (Gougoutsa et al., 2016;Ibrahim and Abu-Shanab, 2013;Jiang et al., 2018;Shahi et al., 2019;Wan et al., 2010). Raw water characteristics are crucial, and many substances were identified as DBPs precursors: NOM (Neale and Leusch, 2019; Sillanp€ a€ a and Matilainen, 2015), pharmaceuticals (Ternes and von Gunten, 2010;Zhou et al., 2016), antibacterial agents (Jeli c et al., 2012), textile dyes (Alves de Lima et al., 2007), pesticides (Duirk and Collette, 2006;Mehrsheikh et al., 2006), bisphenol A (Hu et al., 2002), alkylphenol ethoxylate surfactants (Petrovic et al., 2010) and cyanotoxins (Corbel et al., 2014;Lee et al., 2017). It is more effective to remove DBPs precursors before disinfection or to control its operational parameters than to remove the already formed DBPs (Lin et al., 2016). ...
Article
The occurrence of disinfection byproducts (DBPs) is related both to drinking water treatment (DWT) processes and to raw water’s characteristics. Emerging pollutants typically occur in low concentrations and are not removed by conventional DWT processes. Emerging DBPs appear within the DWT or in the distribution system due to the combination of disinfection agents (especially chlorine) with precursors as: natural organic matter (NOM), algal organic matter (AOM), anthropogenic contaminants (pesticides, pharmaceuticals, detergents etc.), brominated and iodinated compounds. This study has as main goal a consistent analysis of the major problems caused by emerging DBPs to drinking water supplies. It presents a comprehensive review of the research efforts related to emerging DBPs considering three viewpoints: 1. an overview of their classification, legislative framework, methods of analysis, disinfection operational conditions and removal processes; 2. their occurrence, fate, health effects and impacts; 3. the analysis of the advanced DWT processes that might be used for the removal and control of precursors and DBPs, with a focus on pilot and full-scale installations. All presented case studies considered pollutants removed, process conditions and efficiencies, and a critical assessment of processes based on membranes, advanced oxidation and adsorption on activated carbon or other materials. The main challenges of the control and removal of emerging DBPs are their low concentrations and the technical and economic sustainability of their application at full-scale, which need to be carefully adapted to local boundary conditions.
... al, 1988;Trehy et. al, 1981), and others (Scully et al., 1988;McCormick, et al. 1993;Mehrsheikh et al., 2006;Conyers et al., 1997). N-DBPs are of concern to the drinking water industry because they may be more geno-and cytotoxic than many of the currently regulated DBPs (Muellner et al., 2007;Plewa et al., 2008). ...
Article
During the nanofiltration membrane separation of glyphosate mother liquor, a precipitation method was employed to remove HPO32 −, which is often the cause of membrane fouling and blockage. Such removal reduces the speed of membrane flux attenuation. The purpose of the present study was to investigate the effects of precipitant quantity and type, pH value, stirring time and speed, and standing time, on the removal of HPO32 −. In addition, the membrane flux separated by the nanofiltration membrane of the mother liquor post-pretreatment, was tested. Results indicated that when the initial pH was 9, the following pretreatment procedure resulted in the removal of more than 60% of the HPO32 − from the glyphosate mother liquor: the addition of 0.24 mol/L AlCl3·6H2O, stirring at 300 r/min for 30 s and 100 r/min for 2.5 min, followed by standing for 30 min. This pretreatment–precipitation method can markedly enhance the nanofiltration membrane flux in the mother liquor and reduce the membrane flux attenuation, which facilitates nanofiltration membrane separation of the glyphosate mother liquor.
Article
Nitrogen-containing pollutants have been found in surface waters and industrial wastewaters due to their presence in pesticides, dyes, proteins, and humic substances. Treatment of these compounds by conventional oxidants produces disinfection by-products (DBP). Ferrate(VI) (Fe(VI)O(4)(2-), Fe(VI)) is a strong oxidizing agent and produces a non-toxic by-product Fe(III), which acts as a coagulant. Ferrate(VI) is also an efficient disinfectant and can inactivate chlorine resistant microorganisms. A novel ferrate(VI) technology can thus treat a wide range of pollutants and microorganisms in water and wastewater. The aim of this paper is to review the kinetics and products of the oxidation of nitrogen-containing inorganic (ammonia, hydroxylamine, hydrazine, and azide) and organic (amines, amino acids, anilines, sulfonamides, macrolides, and dyes) compounds by ferrate(VI) in order to demonstrate the feasibility of ferrate(VI) treatment of polluted waters of various origins. Several of the compounds can degraded in seconds to minutes by ferrate(VI) with the formation of non-hazardous products. The mechanism of oxidation involves either one-electron or two-electrons processes to yield oxidation products. Future research directions critical for the implementation of the ferrate(VI)-based technology for wastewater and industrial effluents treatment are recommended.
Article
The effect of substituents on the strength of N-X (X = H, F, and Cl) bonds has been investigated using the high-level W2w thermochemical protocol. The substituents have been selected to be representative of the key functional groups that are likely to be of biological, synthetic, or industrial importance for these systems. We interpreted the effects through the calculation of relative N-X bond dissociation energies (BDE) or radical stabilization energies (RSE(NX)). The BDE and RSE(NX) values depend on stabilizing/destabilizing effects in both the reactant molecule and the product radical of the dissociation reactions. To assist us in the analysis of the substituent effects, a number of additional thermochemical quantities have been introduced, including molecule stabilization energies (MSE(NX)). We find that the RSE(NH) values are (a) increased by electron-donating alkyl substituents or the vinyl substituent, (b) increased in imines, and (c) decreased by electron-withdrawing substituents such as CF(3) and carbonyl moieties or through protonation. A different picture emerges when considering the RSE(NF) and RSE(NCl) values because of the electronegativities of the halogen atoms. The RSE(NX)s differ from the RSE(NH) values by an amount related to the stabilization of the N-halogenated molecules and given by MSE(NX). We find that substituents that stabilize/destabilize the radicals also tend to stabilize/destabilize the N-halogenated molecules. As a result, N-F- and N-Cl-containing molecules that include alkyl substituents or correspond to imines are generally associated with RSE(NF) and RSE(NCl) values that are less positive or more negative than the corresponding RSE(NH). In contrast, N-F- and N-Cl-containing molecules that include electron-withdrawing substituents or are protonated are generally associated with RSE(NF) and RSE(NCl) values that are more positive or less negative than the corresponding RSE(NH).
Article
Nanofiltration separation of glyphosate simulated wastewater was investigated using a DK membrane. The effects of operating parameters and the addition of impurities on membrane performance were studied in detail. It was found that at 20 °C, with a glyphosate concentration of 500 mg/L and pH of 2.96, the glyphosate retention rate and the membrane permeate flux increased slightly with increasing transmembrane pressure. With an increase in operating temperature, the permeate flux increased linearly while the retention rate decreased. The permeate flux and glyphosate retention rate decreased with increasing feed concentration. Within the pH range of 3-5, the glyphosate retention rate decreases with increasing pH and reaches a minimum at the isoelectric point of the membrane, while the permeate flux reaches a maximum level at this point. In the pH range of 5-11, with the increases of pH, the glyphosate retention rate increases and the permeate flux decreases. Glyphosate retention decreases slightly with increasing NaCl and phosphite concentrations. This can be explained in terms of the shielding phenomenon.
Article
Amino acids and peptides may form potentially harmful disinfection byproducts during the conventional treatment of water and wastewater. Removal of these parent compounds by the use of the environmental-friendly oxidant, ferrate(VI) (FeVIO42−, Fe(VI)) was assessed by studying the kinetics of the oxidation of glycine (NH3+CH2COOH, Gly) and glycylglycine (NH3+CH2CONHCH2COOH, Gly–Gly) as a function of pH (4.0–12.4) at 25 °C. This study with Gly–Gly represents an initial investigation of oxidation of peptides by Fe(VI). Generally, the second-order rate constant (k) increased with decreased pH in the basic pH region, but this trend was reversed in the acidic pH range. Consideration of the reactivity of three oxidants (H2FeO4, HFeO4−, and FeO42−) with three species of Gly and Gly–Gly (positive, neutral, and negative) reasonably explained the pH dependence of the rates. At pH 9.0, the molar consumption of Fe(VI) was nearly equal to that of Gly. The reaction of Fe(VI) with Gly at molar ratios of 1.0 and 2.0 ([Fe(VI)]:[Gly]) produced ammonia, carbon dioxide, and acetate. A reaction scheme is proposed which explains the formation of these products. The values of k for oxidation of iminodiacetate and nitriloacetate at pH 7.0 were also determined in order to compare oxidation of amines by Fe(VI). The calculated half-lives at neutral pH for the oxidation of primary and secondary amines were in seconds while decomposition of tertiary amines would occur in minutes. Overall, the reactivity of Fe(VI) with Gly and Gly–Gly indicates the significant potential of Fe(VI) to remove amine- and peptide-containing pollutants in water and wastewater.
Article
Cyanobacteria blooms pose an environmental hazard because of the release of water soluble toxic compounds, called cyanotoxins. Microcystins (MCs), hepatotoxic cyclic peptide toxins, are the most widespread cyanotoxins with microcystin-LR (MC-LR) the most common and toxic variant. Health effects of MCs have resulted in the need of using efficient treatment methods for the removal of this class of toxins in water supplies. While physical treatment methods can remove MCs at full or some extent from contaminated water, their function is primary separation of the whole toxins as intact molecules and further processing is required. On the other hand, chemical oxidation processes are a promising alternative treatment option due to the potential of complete destruction of the MCs, transformation to less toxic by-products, and even complete mineralization. MCs reactivity towards different conventional oxidants is strongly affected by water quality parameters like pH, DOC and oxidant dose. Although there is a general trend for MCs oxidation (ozone > permanganate > chlorine >>> chlorine-based oxidants), the selection of the appropriate oxidant for toxin elimination during water treatment should be assessed for each particular source of water. Although advanced oxidation processes are generally more effective on MCs degradation than conventional oxidation processes, scale-up studies are needed before these methods are considered as economically-feasible and practical sustainable alternatives in water treatment facilities. In this review, recent literature concerning treatment of MCs in water by conventional and advanced oxidation processes are reviewed and discussed in terms of the degree of degradation, reaction kinetics, identity and toxicity of oxidation by-products and possible degradation pathways.
Article
Chlorine is the most commonly used chemical for water and wastewater disinfection worldwide, and it reacts with both ammonia and dissolved organic nitrogen. Using the salicylate spectrophotometric method, effects of glycine on the classic breakpoint chlorination are studied using glycine as a surrogate for dissolved organic nitrogen. The results show that the shape of the breakpoint chlorination curve with glycine was analogous to that of water without glycine. Increasing the glycine concentration moves the chlorination breakpoint curve to the right, demonstrating that more chlorine must be added to replace the chlorine consumed by glycine and yield the desired residual active chlorine concentration. At the peak of the chlorination breakpoint curve, both NH2Cl and mono-chlorinated organic chloramine reach their maximum. The Cl2/N ratio of the peak is linearly related to the glycine concentration, and our calculations indicate that the maximum of mono-chlorinated organic chloramine formation by glycine chlorination occurs at a stoichiometric ratio of 1:1; the same as that for chlorinating ammonia to NH2Cl. The distribution of NH2Cl and organic chloramines is controlled by [Gly]/[NH3-N]. At the breakpoint, ammonia and glycine are completely oxidized by chlorine, which leads to chlorine depletion. The stoichiometric ratio for the complete oxidation of glycine was 3:1, larger than that for complete oxidation of ammonia (2:1). For the different stoichiometric ratio in reaction of oxidation of ammonia and glycine, the sum of ammonia and glycine cannot be used as a chlorine dosage control parameter. The chlorine control method involving ammonia and glycine for chlorine and chloramination process is established.
Article
There is renewed interest in the tetra-oxy compound of +6 oxidation states of iron, ferrate(VI) (Fe(VI)O4(2-)), commonly called ferrate. Ferrate has the potential in cleaner ("greener") technologies for water treatment and remediation processes, as it produces potentially less toxic byproducts than other treatment chemicals (e.g., chlorine). Ferrate has strong potential to oxidize a number of contaminants, including sulfur- and nitrogen-containing compounds, estrogens, and antibiotics. This oxidation capability of ferrate combines with its efficient disinfection and coagulation properties as a multi-purpose treatment chemical in a single dose. This review focuses on the engineering aspects of ferrate use at the pilot scale to remove contaminants in and enhance physical treatment of water and wastewater. In most of the pilot-scale studies, in-line and on-line electrochemical ferrate syntheses have been applied. In this ferrate synthesis, ferrate was directly prepared in solution from an iron anode, followed by direct addition to the contaminant stream. Some older studies applied ferrate as a solid. This review presents examples of removing a range of contaminants by adding ferrate solution to the stream. Results showed that ferrate alone and in combination with additional coagulants can reduce total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and organic matter. Ferrate also oxidizes cyanide, sulfide, arsenic, phenols, anilines, and dyes and disinfects a variety of viruses and bacteria. Limitations and drawbacks of the application of ferrate in treating contaminated water on the pilot scale are also presented.
Article
Glyphosate is a broad spectrum, non-selective herbicide, widely used for the post-emergence control of annual and perennial weeds in a variety of applications. Although of low toxicity, its presence in drinking water is undesirable and can cause drinking water compliance failure in the EU if found at concentrations >0.1 mu g L-1. Treatment methods such as ozonation and activated carbon are currently used for pesticide degradation and removal. This article provides a review of the reported efficiency in removal and degradation of glyphosate and aminomethylphosphonic acid (AMPA) by some commonly employed treatment options. Additional experiments have been carried out where knowledge gaps have been identified. Oxidants used in water treatment, particularly Cl-2 and O-3, are highly effective in degrading glyphosate and AMPA. Removal by coagulation and activated carbon is ineffective as a barrier against contamination in drinking water. UV treatment is also ineffective for glyphosate and AMPA degradation but the combination of UV/H2O2 provided significant degradation of glyphosate, but not AMPA, under the conditions investigated. UV/TiO2 treatment can degrade significant amounts of glyphosate but the irradiation time needed is long. Removal or degradation by bank filtration, slow sand filtration, ClO2 and membranes is variable but can provide significant removal under the right conditions.
Chapter
Analysis of inorganic chloramines in waters is of particular interest in the field of drinking waters as they are at the origin of many others disinfection by-products (DBPs). They are formed when free chlorine reacts with nitrogen containing substances present in chlorinated water sources. Their presence is generally unwanted (except for monochloramine when used a secondary disinfectant) and bears witness of the presence of other potentially more toxic DBPs. Their analysis is also challenging because of their high reactivities, unstabilities in waters, low molecular weight, and high polarity. This chapter introduces first the physical-chemical properties of inorganic chloramines presents, then their modes of preparation (as no standard of inorganic chloramines are commercially-available), and finally the different methods available for analysis of total chloramines and for discrimination of monochloramine, dichloramine and trichloramine, in waters.
Article
Glyphosate, one of the organophosphate herbicides, has been widely used in the word. The removal of glyphosate was comparatively investigated by MnO2 oxidation, electrochemical oxidation, and electrochemically assisted MnO2 oxidation (electro-MnO2) processes. The effects of MnO2 dosage, current density, and solution pH on glyphosate removal and Mn2+ release were examined. The results indicated that the removal of glyphosate by MnO2 oxidation favored acidic pH conditions and a large portion of Mn2+ ions were released from MnO2. With the electro-MnO2 process using RuO2/TiO2 coated titanium mesh as both anode and cathode, glyphosate removal was significantly promoted and most of the released Mn2+ ions were oxidatively reverted to MnO2, which in turn enhanced the removal of glyphosate. Solution pH exerted an insignificant effect on glyphosate removal in the electro-MnO2 process. Major reaction intermediates including sarcosine, glycine, and PO43- were indentified in the initial phase of the MnO2 oxidation and electro-MnO2 processes. Glycine was further decomposed to glycolic acid and NH3-N in the MnO2 oxidation process; in contrast, glycine was oxidized into oxamic acid, glycolic acid and N-contained intermediates, and N-contained intermediates could be finally oxidized into acetic acid, NH3-N and NO3--N in the electro-MnO2 process. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.
Chapter
Explains the role of reactive intermediates in biological systems as well as in environmental remediation. With its clear and systematic approach, this book examined the broad range of reactive intermediate that can be generated in biological environments, detailing the fundamental properties of each reactive intermediate. Readers gain a contemporary understanding of how these intermediates react with different compounds, with an emphasis on amino acids, peptides, and proteins. The author not only sets forth the basic chemistry and nature of reactive intermediates, he also demonstrates how the properties of the intermediates presented in the book compare with each other. Oxidation of Amino Acids, Peptides, and Proteins begins with a discussion of radical and non-radical reactive species as well as an exploration of the significance of reactive species in the atmosphere, disinfection processes, and environmental remediation. Next, the book covers such topics as: Thermodynamics of amino acids and reactive species and the effect of metal-ligand binding in oxidation chemistry. Kinetics and mechanisms of reactive halogen, oxygen, nitrogen, carbon, sulfur and phosphate species as well as reactive high-valent Cr, Mn, and Fe species. Reactivity of the species with molecules of biological and environmental importance. Generation of reactive species in the laboratory for kinetics studies. Oxidation of amino acids, peptides, and proteins by permanganate, ferryl, and ferrate species. Application of reactive species in purifying water and treating wastewater. With this book as their guide, readers will be able to assess the overall effects of reactive intermediates in biological environments. Moreover, they'll learn how to apply this knowledge for successful water purification and wastewater treatment.
Article
Amino acids (AAs) are known precursors to regulated and unregulated disinfection by-products (DBPs). Nitrogenous DBPs are of concern in the drinking water industry because they can be more geno- and cytotoxic than many of the currently regulated carbon-based DBPs. The authors measured occurrences and removals of AAs in raw water and filter effluents from 16 full-scale drinking water treatment plants that treat water impaired by upstream wastewater discharge or algal growth. The AAs measured in this study accounted for only a small portion of the dissolved organic nitrogen (DON) pool and were removed, to a high degree, during drinking water treatment. This work illustrates that although amino acids can account for a more significant portion of the DON pool in natural lakes and streams, the influence of wastewater discharge and algal activity produce a pool of organic nitrogen not likely to account for all of the nitrogenous DBPs. This unidentified DON warrants identification and further study.-SB.
Article
Ferric supported active carbon was prepared by impregnation-calcination method and the characteristics of its surface were investigated by scanning electron magnification (SEM), and both adsorption isotherm and adsorption kinetics of Fe-AC were studied. The effects of different factors on the adsorption process were also studied. Freundlich equation fitted well to supported ferric active carbon adsorption isotherm, the maximum adsorption capacity was 5.8 mmol/g; and the adsorption kinetics was fitted well by Lagergren equation, so adsorption rate constant can be calculated out 0.088 min-1 that can decrease with the temperature increase. According to Kannan & Sundaram internal diffusion model, the internal diffusion constant was higher than 10 mg·min-1/2/g, which decreased with the temperature increase. Due to the ionization form of glyphosate and the change of Fe-AC surface characteristics, the adsorption capacity of glyphosate decreased when the pH of solution increased. Antagonistic effect caused the adsorption capacity decrease of Fe-AC due to the existence of NaCl, and when the concentration of NaCl reached 4 g/L, salting-out effect became dominant, which increased the adsorption capacity slightly. Because of the steric hindrance of glyphosate and the complex formation between phosphate and supported ferric active carbon surface, the Fe-AC adsorption capacity decreased continuously while the concentration of phosphate increase.
Chapter
Environmentally significant concentrations of organic contaminants (emerging and others) are normally in the range 10–104 ng/L. For their targeted analysis mostly liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) techniques are used. However, an unambiguous structure elucidation of unknown contaminants and transformation products cannot always be achieved by these methods. Nuclear magnetic resonance (NMR) is a powerful tool for the structure elucidation of unknown compounds and provides important information complementary to that of MS. However, NMR can be used only if compound concentrations are at least in the upper ng range. The aim of this chapter is to demonstrate with examples the current possibilities of NMR techniques for the analysis of emerging and other contaminants and of their transformation products in aqueous environmental samples. First basic techniques of sample enrichment and clean-up, tube NMR and hyphenated NMR techniques such as LC-NMR, LC-NMR-(HR)MS, LC-SPE-NMR-(HR)MS are briefly described. Next, papers with the following topics are reviewed: (i) The use of MS and NMR methods for the structure elucidation of unknown metabolites and disinfection by-products which were isolated from laboratory-scale studies. (ii) The direct identification of organic contaminants in aqueous samples from contaminated point sources by MS and/or hyphenated NMR techniques. (iii) The comprehensive NMR characterization of complex technical mixtures that forms a prerequisite for the targeted analysis of their single components in environmental matrices. (iv) Applications of site-specific natural-isotope fractionation nuclear magnetic resonance (SNIF-NMR). The cited literature covers the range from 2005 to 2012 but there is no claim to completeness.
Article
We have developed a simultaneous analytical method for pesticides by gas chromatography mass spectrometry (GC/MS) , liquid chromatography mass spectrometry (LC/MS) or liquid chromatography-inductively coupled plasma mass spectrometry (LC/ICP/MS) . We applied this method to 195 pesticides that are frequently used or are “Complementary Items” in drinking water in Japan, and found that 192 of them could be analyzed. The recovery rates of the compounds from the river water and groundwater samples were within the range of 70-130%, with relative standard deviations of less than 20%. Considering the degradation by chlorination, the target pesticides were classified into 10 categories on the basis of the reaction rate constant. The structures of transformation products generated by chlorination were predicted using the mass spectrum and accurate mass that were obtained by liquid chromatography time-of-flight mass spectrometry (LC/TOF-MS) .
Article
A screening technique has been developed that allows the rapid, real-time detection and identification of major transformation products of organic contaminants during aqueous oxidation experiments. In this technique, a target contaminant is dissolved in buffered water and chlorinated by the addition of sodium hypochlorite to give a free chlorine residual of 3 mg/L. Solution from the reaction vessel is combined with methanol and pumped directly into the electrospray ionization source of a quadrupole time-of-flight mass spectrometer (QTOF MS). The real-time decay of the target contaminant and the formation/decay of transformation products are then monitored using the QTOF MS. Subsequently, accurate mass measurements with internal mass calibration (<5 ppm mass error) and product ion scans are employed to identify these transformation products. Unlike other techniques, it requires no liquid chromatography, derivatization, or quenching of residual chlorine, all of which can interfere with transformation product analysis. To validate the technique, aqueous chlorination experiments were performed on triclosan, a previously studied environmental contaminant. Earlier research showing that triclosan underwent chlorine addition to form mono- and dichlorinated transformation products was successfully reproduced, demonstrating the feasibility of the technique. In addition, the technique revealed the formation of a stable oxygen radical-containing transformation product resulting from the oxidation of either mono- or dichlorinated triclosan. This triclosan transformation product was determined to have an empirical formula of C12H4O3Cl4 with 3.9 ppm mass error. Furthermore, atorvastatin, a commonly prescribed medication and environmental contaminant, was subjected to aqueous chlorination and studied with the technique. Atorvastatin underwent hydroxylation to form two transformation products with the empirical formulas C33H34FN2O6 (1.8 ppm mass error) and C26H29O5NF (2.9 ppm mass error).
Article
The mechanism of reaction of glycine with hypochlorite was investigated under neutral conditions in phosphate buffer. At the first stage in this reaction, monochloroglycine was formed at any molar ratio of glycine and hypochlorite. When the amount of hypochlorite exceeded the equimolar of glycine, dichloroglycine was formed from monochloroglycine. Although monochloroglycine was fairly stable, dichloroglycine was labile, so that it underwent decarboxylation and dehydrochlorination to form cyanide, as the corresponding nitrile. Cyanide thus formed was chlorinated rapidly by combined residual chlorine in chloroglycine molecules or by excess hypochlorite, and converted to cyanogen chloride. One mole glycine needed three moles of hypochlorite for the formation of the equivalent cyanogen chloride. Cyanogen chloride was decreased by the subsequent addition of excess hypochlorite. Total chlorine consumed by 1 mol glycine was 4.5 mol. © 1983, The Pharmaceutical Society of Japan. All rights reserved.
Article
Glyphosate-based weed control products are among the most widely used broad-spectrum herbicides in the world. The herbicidal properties of glyphosate were discovered in 1970, and commercial formulations for nonselective weed control were first introduced in 1974 (Franz et al. 1997). Formulations of glyphosate, including Roundup® Herbicide (RU)1 (Monsanto Company, St. Louis, MO), have been extensively investigated for their potential to produce adverse effects in nontarget organisms. Governmental regulatory agencies, international organizations, and others have reviewed and assessed the available scientific data for glyphosate formulations and independently judged their safety. Conclusions from three major organizations are publicly available and indicate RU can be used with minimal risk to the environment (Agriculture Canada 1991; USEPA 1993a; WHO 1994). Several review publications are available on the fate and effects of RU or glyphosate in the environment (Carlisle and Trevors 1988;Smith and Oehme 1992 ; Malik et al. 1989;Rueppel et al. 1977; Sullivan and Sullivan 1997;Forestry Canada, 1989). In addition, several books have been published about the environmental and human health considerations of glyphosate and its formulations (Grossbard and Atkinson 1985; Franz et al. 1997). In addition, RU and other glyphosate formulations have been selected for use in a number of weed control programs for state and local jurisdictions in the United States. Many of these uses require that ecological risk assessments be conducted in the form of Environmental Impact Statements or Environmental Assessments. These documents are comprehensive and specific to local use situations. Documents are available for risk assessments in Texas, Washington, Oregon, Pennsylvania, New York, Virginia, and other states (USDA 1989;USDA 1992;USDA 1996;USDA 1997;USDI 1989; Washington State DOT 1993).
Article
Ozonation of the complexing agent ethylenediaminetetra(methylenephosphonic acid) (EDTMP) was studied with bench-scale experiments. As it turned out that EDTMP is totally oxidized within a few seconds, a mechanism for the reaction of EDTMP with ozone is presented which predicts the formation of the herbicide N-phosphonomethylglycine (glyphosate) and its major metabolite aminomethylphosphonic acid (AMPA). The experimental results confirm the predicted mechanism as well as the formation of glyphosate and AMPA during ozonation of waters containing EDTMP.
Article
Activated-carbon, oxidation, conventional-treatment, filtration, and membrane studies are conducted to determine which process is best suited to remove the herbicide glyphosate from potable water. Both bench-scale and pilot-scale studies are completed. Computer models are used to evaluate the results. The activated-carbon results show that glyphosate adsorbs very strongly in distilled water, but has a much lower capacity in Ohio River water. The jar-test studies with an alum coagulant show that as turbidity is removed, so is glyphosate. The majority of the glyphosate removal occurs as turbidity is reduced below 2 nephelometric turbidity units (NTUs). Powdered-activated-carbon treatment is ineffective. Ultrafiltration membranes and 0.45 μm filters do not remove glyphosate in Ohio River water even though the effluent turbidity is reduced below 0.2 NTU. The oxidation results indicate that glyphosate is easily destroyed by chlorine and ozone. Chlorine dioxide, permanganate, and hydrogen peroxide are less successful. These conventional-treatment and adsorption results are confirmed by pilot-scale studies.
Article
The hydrolysis of cyanogen chloride has been studied in buffered media. Rate equations have been derived, general base catalysis has been identified, and the activation energy of the reaction has been measured. The effects of several additives on the rate of hydrolysis have been examined. The chlorine-catalysed hydrolysis has been investigated and the catalytic species has been conclusively identified as dissolved molecular chlorine.
Article
Following the estimation by Ramsey of the absolute value for the paramagnetic contribution (σ_p) to the absolute shielding of ^(15)N_2 relative to the bare nucleus ^(15)N, considerable interest has been expressed3 in establishing an absolute shielding scale for ^(14)N (and ^(15)N) nuclear magnetic resonance. This requires ^(15)N chemical shifts referenced to the ^(15)N_2 resonance via some secondary standard, usually ^(15)NH_4^+ or ^(15)NO_3^- in aqueous solution. To date, two measurement of the resonance position of ^(14)N_2 have been published as 14 and 70 ppm upfield from ^(14)NO_3^-, but doubts have been expressed about the accuracy of these values. One source of uncertainty in the reported chemical shifts arises from the line widths of the ^(14)N resonances. From the relaxation time data for liquid ^(14)N_2 at 77ºK of Armstrong and Speight, we estimate the width at half height of the ^(14)N resonance to be ca. 30 Hz (9.5 and 7 ppm at 10 and 13 kG, respectively.
Article
Formaldehyde hydration has been studied with pulse polarography in acetate and phosphate buffers, at 25°C. It could be shown that in both buffer systems extrapolation to zero buffer concentration produces the equilibrium constant Kd=[CH2O]/[CH2(OH)2]=(6.31±0.05) 10−4 in pure water, a value of as yet unmatched precision. In the buffers mentioned two novel features appear in the hydration mechanism: (a) buffer acids form addition compounds with CH2O where the, corresponding equilibria are rapidly established. The equilibrium constants have been derived. (b) H2PO4−/HPO42− buffers are exceptional in that the polarographic specific rate of hydration as a function of the concentration of this buffer is less than expected on the basis of a normal linear dependence. This is explained, as in the case of free-aldehyde glucose [23], on the basis of a solvent (water)-shared associate of (presumably) H2PO4− with CH2O which decreases the rate of diffusion of the latter, the more so as the buffer concentration increases. It is pointed out, that the occurrence of such associates can explain the excess activity of H2PO4− as an acid catalyst in aldehyde hydration [16].
Article
The reaction of chlorination of α-amino acids for 6 < pH < 11 has been studied. The reaction is an aliphatic electrophilic substitution, the rate determining step being the transfer of the chlorine atom between the HOCl oxygen and the nitrogen of the α-amino acid free amino group.
Article
Aqueous solutions containing six model organic-N compounds (glycine, cysteine, asparagine, uracil, cytosine, and guanine) were subjected to chlorination at various chlorine (Cl) to precursor (P) molar ratios for 30 min. Chlorine residuals were determined by both DPD/FAS titration and the MIMS (Membrane Introduction Mass Spectrometry) method to evaluate breakpoint chlorination behavior, residual chlorine distributions, and byproducts. DPD/FAS titration was found to yield false-positive measurements of inorganic combined chlorine residuals in all cases. The breakpoint chlorination curve shape was strongly influenced by the structure of the model compound. Cyanogen chloride was found to be present as a byproduct in all cases, and the yield was strongly dependent on the Cl:P molar ratio and the structure of the compounds, with glycine being the most efficient CNCl precursor. Six byproducts other than cyanogen chloride were also identified. Free chlorine measurements by DPD/FAS titration and MIMS were in good agreement. This finding, together with the results of previously conducted research, suggests that both methods are capable of yielding accurate measurements of free chlorine concentration, even in solutions that contain complex mixtures of +1-valent chlorine compounds.
Article
Methanediol dehydrates to give formaldehyde, which reacts rapidly and reversibly with monochloramine to form N-chloroaminomethanol. Under drinking water conditions, N-chloroaminomethanol undergoes a relatively slow decomposition that eventually leads to the formation of cyanogen chloride (ClCN) in apparently stoichiometric amounts. The following reaction sequence is proposed:  CH2(OH)2 CH2O + H2O; CH2O + NH2Cl CH2(OH)NHCl; CH2(OH)NHCl → CH2NCl + H2O; CH2NCl → HCl + HCN; CN- + NH2Cl + H+ → ClCN + NH3. These reactions were studied at 25.0 °C and an ionic strength of 0.10 M (NaClO4). Stopped-flow photometry was used to monitor rapid, reversible reactions, and photometry was used to study relatively slow decomposition reactions. Equilibrium and rate constants for the addition of formaldehyde to monochloramine were (6.6 ± 1.5) × 105 M-1 and (2.8 ± 0.1) × 104 M-1 s-1, respectively. The dehydration of N-chloroaminomethanol was catalyzed by both H+ and OH-, with respective rate constants of 277 ± 7 and 26.9 ± 5.6 M-1 s-1. Under characteristic drinking water conditions, the decay of N-chloroaminomethanol is the rate-limiting step. N-Chloromethanimine, formed by the dehydration of N-chloroaminomethanol, had a decomposition rate constant of (6.65 ± 0.06) × 10-4 s-1. At the relatively high methanediol concentrations used in this study, the intermediary N-chlorodimethanolamine was formed by the rapid and reversible reaction of N-chloroaminomethanol with formaldehyde. N-Chlorodimethanolamine then decayed relatively slowly. The following reaction sequence is proposed:  CH2(OH)NHCl + CH2O {CH2(OH)}2NCl; {CH2(OH)}2NCl → CH2NCl + CH2O + H2O. The equilibrium and rate constants for the addition of formaldehyde to N-chloroaminomethanol were (9.5 ± 2.5) × 104 M-1 and (3.6 ± 0.1) × 103 M-1 s-1, respectively. The decomposition of N-chlorodimethanolamine was catalyzed by OH-, with a rate constant of 19.2 ± 3.7 M-1 s-1. N-Chlorodimethanolamine would not be present under typical drinking water treatment conditions.
Article
Model solutions of the dipeptide glycylphenylalanine were chlorinated at pH 7.0 to five different chlorine-to-peptide (Cl2/peptide) mole ratios and analyzed after 30 min by high-performance liquid chromatography. At Cl2/peptide mole ratios ≤ 1, N-chloroglycylphenylalanine (I) appears to be the only product. At mole ratios ≥ 2, N,N-dichloroglycylphenylalanine (II) was the only product. II decomposes in model solutions (t1/2 = 6.4 h) at pH 7.0 to form a compound tentatively identified as N-[2-(N‘-chloroimino)ethanoyl]phenylalanine (III), an N-chloroaldimine. III, in turn, decomposes (t1/2 = 36 h) to IV. From 13C- and 1H-NMR, GC/MS, and IR, IV was identified as N-cyanoacylphenylalanine. Glycyl-p-[3H]-phenylalanine (VI) was synthesized in order to monitor the reaction at low concentrations of the compound in a wastewater. A secondary wastewater (TKN = 1.29 mg of N/L; [NH3]= 0.074 mg of N/L) was inoculated with VI and chlorinated to nine different chlorine concentrations. The stabilities of the tritiated analogs of II and III in the wastewater were comparable to those determined in model solutions.
Article
Solutions of the amino acid isoleucine were chlorinated to different chlorine to nitrogen mole ratios and analyzed by ultraviolet spectroscopy, gas chromatography, and high-performance liquid chromatography (HPLC). The mono-N-chlorinated amino acid, 2-methylbutyraldehyde, and 2-methylbutyronitrile were products, the yields of which varied with chlorination level. At Cl/N mole ratios greater than 2 a previously undetected N-chlorinated aldimine, which was remarkably stable in the absence of ammonia, was the main product. The concentration of isoleucine in an unchlorinated primary municipal wastewater effluent was determined. The products of its chlorination and their yields at different Cl/N ratios were determined by using a radiotracer and were found to be similar to those observed in model solutions. A scheme of pathways for the formation of the various products from the chlorination of isoleucine is proposed. This work suggests that N-chloroaldimines may contribute significantly to a stable combined oxidant concentration in wastewaters chlorinated to a free residual.
Article
The chlorination reactions of phenylalanine in water and wastewater were studied. At the lower CI/N molar ratios N-chlorophenylalanine and phenylacetaldehyde were identified as the main products while phenylacetonitrile and N-chlorophenylacetaldimine were the major products at Cl/N ratios of 2.0 and beyond. The concentration of phenylalanine in a primary municipal wastewater effluent was determined, and the chlorination products were found to be the same as those in model solutions. N-Chlorophenylacetaldimine decomposes slowly (t1/2 = 35 h) in water (pH 7.0 and 8.0) and in wastewater (pH 7.0, estimated t1/2 of 58 h). The distribution of chlorination products in the wastewater supports the theory that monochlorinated organic amino nitrogen compounds may represent a disproportionately high fraction of the chlorine-containing oxidants present in marginally chlorinated primary effluent.
Article
The chlorination reactions of valine in water and wastewater were studied. N-Chlorovaline and isobutyraldehyde were the main products at Cl/N molar ratios of <1, while isobutyronitrile and N-chloroisobutyraldimine were the major products at Cl/N ratios of 2.0 and beyond. N-Chloroisobutyraldimine was identified by gas chromatography/mass spectroscopy and infrared and nuclear magnetic resonance spectroscopy. The concentration of valine in a primary municipal wastewater effluent was determined. The amounts and identity of its chlorination products in wastewater were determined by using a radiotracer and were found to be similar to those found in the model solutions. N-Chloroisobutyraldimine is stable in dilute aqueous solution with a half-life of 34 h. A mechanism for the formation of the chlorination products of valine is proposed.
Article
A study of the reactions of sodium and calcium hypochlorites with buffered alkaline solutions of potassium cyanide indicated that the first product was always cyanogen chloride, which was rapidly hydrolysed at pH II or above without further absorption of available chlorine. At lower pH values additional chlorine was absorbed up to a total of 5·75 gram-atoms per gram-molecule of cyanide. At pH II the reaction of hypochlorites with the complex cyanides of zinc and cadmium was similar to that with potassium cyanide; cupro-cyanide was also rapidly attacked, with oxidation of cuprous copper to the cupric state, but nickelocyanide was only slowly attacked.A process was developed for treating electroplating wastes, or other waste waters containing cyanide, by reaction with calcium hypochlorite at pH II. The process would be applicable to liquids containing simple cyanides and the complex cyanides of zinc, cadmium, and copper, but not to solutions containing nickel.
Article
To explain some of the possible origins of an odor episode which took place in a drinking water supply in the region of Paris (France), the chlorination reaction in water of phenylalanine was studied. This amino acid was chosen for first experiments because of its physical and chemical particular properties. Changes in the different byproducts formed were followed by high-performance liquid chromatography (HPLC) over a period of time. N-chlorophenylalanine (mono-N-chlorinated amino acid) and then phenylacetaldehyde were the major products formed for the lower chlorine to nitrogen molar ratios. For Cl/N molar ratios of 1 and beyond, phenylacetonitrile and N-chlorophenylacetaldimine appeared and increased with the chlorination level. N-chlorophenylacetaldimine was quantified by using its difference of stability in various organic solvents. Our attention was first directed to the monochlorinated derivative but further examination indicated that it could not be responsible for odor troubles: it dissociated before reaching the consumer's tap and it was produced at consistently low yields under conditions relevant to drinking water treatment. On the contrary, chloroaldimine appeared to be a very odorous and water-stable product: it strongly smells of swimming pool with a floral background. The odor detection threshold is about 3 microg x L(-1) and it can persist for more than one week at 18 degrees C. It is now suspected of being a source of off-flavor concerns among consumers.
Article
Cyanogen chloride (CNCl) is a disinfection byproduct found in chlorinated and chloraminated drinking water. Although there is an apparent greater association of CNCI with chloraminated water relative to chlorination systems, it was not clear whether these phenomenological observations are explained by differences in the stability or formation potentials of CNCI between the two disinfectants. In this study, the stability of CNCl was examined in the presence of free chlorine and monochloramine using membrane introduction mass spectrometry. CNCI decomposes relatively rapidly when free chlorine is present but is stable in the presence of monochloramine. The decomposition kinetics and observed reaction products are consistent with a hypochlorite-catalyzed hydrolysis mechanism, and the rate law is described by (d[CNCl]/dt) = - kOCl[CNCl][OCl-]. At 25 degrees C, pH 7, and a free chlorine residual of 0.5 mg/L as Cl2, the half-life of CNCl is approximately 60 min, suggesting significant decomposition is expected over disinfection time scales. Under some winter season temperature conditions, however, the decay half-life of CNCl can be longer than typical disinfection contact times. The results of this study demonstrate that the observed association of CNCl with chloramination systems can in part be explained by the differences in its stability with chlorine and chloramines.
Article
In this study, membrane introduction mass spectrometry (MIMS) was applied to evaluate the kinetics of cyanogen chloride (ClCN) destruction by chemical reduction methods, using thiosulfate, sulfite, metabisulfite, ferrous ions and zero-valent iron at various concentrations and pH. The ClCN destruction followed second-order reaction kinetics in all cases of using sulfur compounds, though the second-order rate constants varied substantially from approximately 0.3-25.7 M(-1)s(-1) under different experimental conditions. The destruction of ClCN was primarily attributable to the chemical reduction pathway. Hydroxide-assisted ClCN hydrolysis was only significant at pH 9 and also when the observed reduction rate was relatively slow. The second-order rate constants achieved by sulfur(IV) compounds in the form of sulfite were found to be higher than those obtained with thiosulfate and S(IV) compounds in the form of bisulfite. Ferrous ions and zero-valent iron demonstrated slow or no ClCN reduction up to dosages of 1000 mgL(-1) and 100 gL(-1), respectively. These findings suggest that applying moderately high dosages of S(IV) compounds under neutral or alkali conditions with sufficient contact time is required for wastewater ClCN destruction. In addition, ClCN losses during long-term preservation with excess reducing sulfur compounds prior to analysis can be substantial and should be avoided.
Article
Chlorination reactions of glyphosate, glycine, and sodium cyanate were conducted in well-agitated reactors to generate experimental kinetic measurements for the simulation of chlorination kinetics under the conditions of industrial water purification plants. The contribution of different by-products to the overall degradation of glyphosate during chlorination has been identified. The kinetic rate constants for the chlorination of glyphosate and its main degradation products were either obtained by calculation according to experimental data or taken from published literature. The fit of the kinetic constants with experimental data allowed us to predict consistently the concentration of the majority of the transitory and terminal chlorination products identified in the course of the glyphosate chlorination process. The simulation results conducted at varying aqueous chlorine/glyphosate molar ratios have shown that glyphosate is expected to degrade in fraction of a second under industrial aqueous chlorination conditions. Glyphosate chlorination products are not stable under the conditions of drinking water chlorination and are degraded to small molecules common to the degradation of amino acids and other naturally occurring substances in raw water. The kinetic studies of the chlorination reaction of glyphosate, together with calculations based on kinetic modeling in conditions close to those at real water treatment plants, confirm the reaction mechanism that we have previously suggested for glyphosate chlorination.
Glyphosate herbicide analysis by liquid chromatography with postcolumn reaction detection: column comparison and application notes
  • Miles
Miles, C.J., Leong, G., 1992. Glyphosate herbicide analysis by liquid chromatography with postcolumn reaction detection: column comparison and application notes. LC-GC 10, 452-458.
Glyphosate: A Unique Global Herbicide
  • J E Franz
  • M K Mao
  • J A Sikorski
Franz, J.E., Mao, M.K., Sikorski, J.A., 1996. Glyphosate: A Unique Global Herbicide. ACS Monograph no. 189. American Chemical Society, Washington, DC, pp. 29-64.
  • S D Faust
  • M A Osman
Faust, S.D., Osman, M.A., 1999. Chemistry of Water Treatment, second ed. Lewis Publishers, Boca Raton, FL.