Reactions of chlorine with inorganic and organic compounds during water treatment—Kinetics and mechanisms: A critical review
TL;DR: Comparison of chlorine to ozone reactivity towards aromatic compounds (electrophilic attack) shows a good correlation, with chlorine rate constants being about four orders of magnitude smaller than those for ozone.
About: This article is published in Water Research.The article was published on 2008-01-01. It has received 1579 citations till now. The article focuses on the topics: Chlorine & Electrophilic substitution.
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TL;DR: It was found that ozonation, Fenton/photo-Fenton and semiconductor photocatalysis were the most tested methodologies and combined processes seem to be the best solution for the treatment of effluents containing antibiotics, especially those using renewable energy and by-products materials.
1,219 citations
TL;DR: In this critical review, some of the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants are discussed in detail and the critical assessment of the reactors that can be used to put these technologies into practice is devoted.
Abstract: Traditional physicochemical and biological techniques, as well as advanced oxidation processes (AOPs), are often inadequate, ineffective, or expensive for industrial water reclamation. Within this context, the electrochemical technologies have found a niche where they can become dominant in the near future, especially for the abatement of biorefractory substances. In this critical review, some of the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants are discussed in detail with the following goals: (1) to present the fundamental aspects of the selected processes; (2) to discuss the effect of both the main operating parameters and the reactor design on their performance; (3) to critically evaluate their advantages and disadvantages; and (4) to forecast the prospect of their utilization on an applicable scale by identifying the key points to be further investigated. The review is focused on the direct electrochemical oxidation, the indirect electrochemical oxidation mediated by electrogenerated active chlorine, and the coupling between anodic and cathodic processes. The last part of the review is devoted to the critical assessment of the reactors that can be used to put these technologies into practice.
1,197 citations
TL;DR: An extensive view on the role of hydroxyl radical in different environmental compartments and in laboratory systems is provided, with the aim of drawing more attention to this emerging issue of great concern.
Abstract: The hydroxyl radical (•OH) is one of the most powerful oxidizing agents, able to react unselectively and instantaneously with the surrounding chemicals, including organic pollutants and inhibitors. The •OH radicals are omnipresent in the environment (natural waters, atmosphere, interstellar space, etc.), including biological systems where •OH has an important role in immunity metabolism. We provide an extensive view on the role of hydroxyl radical in different environmental compartments and in laboratory systems, with the aim of drawing more attention to this emerging issue. Further research on processes related to the hydroxyl radical chemistry in the environmental compartments is highly demanded. A comprehensive understanding of the sources and sinks of •OH radicals including their implications in the natural waters and in the atmosphere is of crucial importance, including the way irradiated chromophoric dissolved organic matter in surface waters yields •OH through the H2O2-independent pathway, and the ...
892 citations
TL;DR: This study is the first to demonstrate the contributions of different reactive species to the micropollutant degradation in the UV/chlorine system under environmentally relevant conditions.
Abstract: The UV/free chlorine process forms reactive species such as hydroxyl radicals (HO•), chlorine atoms (Cl•), Cl2•–, and O•–. The specific roles of these reactive species in aqueous micropollutant degradation in the UV/chlorine process under different conditions were investigated using a steady-state kinetic model. Benzoic acid (BA) was chosen as the model micropollutant. The steady-state kinetic model developed fitted the experimental data well. The results showed that HO• and Cl• contributed substantially to BA degradation, while the roles of the other reactive species such as Cl2•– and O•– were negligible. The overall degradation rate of BA decreased as the pH increased from 6 to 9. In particular, the relative contributions of HO• and Cl• to the degradation changed from 34.7% and 65.3% respectively at pH 6 to 37.9% and 62% respectively at pH 9 under the conditions evaluated. Their relative contributions also changed slightly with variations in chlorine dosage, BA concentration and chloride concentration. ...
721 citations
TL;DR: A critical review of recent research identifies future opportunities and research needed to overcome major challenges that currently limit the application of electrochemical water treatment systems for industrial and municipal water and wastewater treatment.
Abstract: Electrochemical processes have been extensively investigated for the removal of a range of organic and inorganic contaminants. The great majority of these studies were conducted using nitrate-, perchlorate-, sulfate-, and chloride-based electrolyte solutions. In actual treatment applications, organic and inorganic constituents may have substantial effects on the performance of electrochemical treatment. In particular, the outcome of electrochemical oxidation will depend on the concentration of chloride and bromide. Formation of chlorate, perchlorate, chlorinated, and brominated organics may compromise the quality of the treated effluent. A critical review of recent research identifies future opportunities and research needed to overcome major challenges that currently limit the application of electrochemical water treatment systems for industrial and municipal water and wastewater treatment. Given the increasing interest in decentralized wastewater treatment, applications of electrolytic systems for treat...
716 citations
References
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TL;DR: The U.S. Geological Survey used five newly developed analytical methods to measure concentrations of 95 organic wastewater contaminants (OWCs) in water samples from a network of 139 streams across 30 states during 1999 and 2000 as mentioned in this paper.
Abstract: To provide the first nationwide reconnaissance of the occurrence of pharmaceuticals, hormones, and other organic wastewater contaminants (OWCs) in water resources, the U.S. Geological Survey used five newly developed analytical methods to measure concentrations of 95 OWCs in water samples from a network of 139 streams across 30 states during 1999 and 2000. The selection of sampling sites was biased toward streams susceptible to contamination (i.e. downstream of intense urbanization and livestock production). OWCs were prevalent during this study, being found in 80% of the streams sampled. The compounds detected represent a wide range of residential, industrial, and agricultural origins and uses with 82 of the 95 OWCs being found during this study. The most frequently detected compounds were coprostanol (fecal steroid), cholesterol (plant and animal steroid), N,N-diethyltoluamide (insect repellant), caffeine (stimulant), triclosan (antimicrobial disinfectant), tri(2-chloroethyl)phosphate (fire retardant), and 4-nonylphenol (nonionic detergent metabolite). Measured concentrations for this study were generally low and rarely exceeded drinking-water guidelines, drinking-water health advisories, or aquatic-life criteria. Many compounds, however, do not have such guidelines established. The detection of multiple OWCs was common for this study, with a median of seven and as many as 38 OWCs being found in a given water sample. Little is known about the potential interactive effects (such as synergistic or antagonistic toxicity) that may occur from complex mixtures of OWCs in the environment. In addition, results of this study demonstrate the importance of obtaining data on metabolites to fully understand not only the fate and transport of OWCs in the hydrologic system but also their ultimate overall effect on human health and the environment.
7,036 citations
"Reactions of chlorine with inorgani..." refers background in this paper
...Although usually present in low concentrations (ng L 1-mg L 1), numerous of these compounds have been reported in groundwaters and surface waters (Blackburn and Waldock, 1995; Ternes, 1998; Hirsch et al., 1999; Kolpin et al., 2002; Ying et al., 2002)....
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TL;DR: In this article, the occurrence of 32 drug residues belonging to different medicinal classes like antiphlogistics, lipid regulators, psychiatric drugs, antiepileptic drugs, betablockers and β 2 -sympathomimetics as well as five metabolites has been investigated in German municipal sewage treatment plant (STP) discharges, river and stream waters.
3,015 citations
TL;DR: In this article, rate constants have been compiled for reactions of various inorganic radicals produced by radiolysis or photolysis, as well as by other chemical means in aqueous solutions.
Abstract: Rate constants have been compiled for reactions of various inorganic radicals produced by radiolysis or photolysis, as well as by other chemical means in aqueous solutions. Data are included for the reactions of ⋅CO2 −, ⋅CO3⋅−, O3, ⋅N3, ⋅NH2, ⋅NO2, NO3⋅, ⋅PO32−, PO4⋅2−, SO2⋅ −, ⋅SO3 −, SO4⋅−, ⋅SO5⋅−, ⋅SeO3⋅ −, ⋅(SCN)2⋅ −, ⋅CL2⋅−, ⋅Br2⋅ −, ⋅I2⋅ −, ⋅ClO2⋅, ⋅BrO2⋅, and miscellaneous related radicals, with inorganic and organic compounds.
2,958 citations
"Reactions of chlorine with inorgani..." refers background in this paper
...18 represents a correlation between HOCl and O3 rate constants for aromatic compounds for which electrophilic ozone and chlorine attack on the aromatic ring is expected (ozone rate constants are taken from Neta et al. (1988), Huber et al. (2003) or Deborde et al. (2005) in Table 7)....
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2,475 citations
"Reactions of chlorine with inorgani..." refers background in this paper
...Soluble inorganic arsenic occurs in surface waters and groundwaters mainly as a combination of As(III) and As(V) (Cullen and Reimer, 1989)....
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01 Jan 2002
TL;DR: Results of this study demonstrate the importance of obtaining data on metabolites to fully understand not only the fate and transport of OWCs in the hydrologic system but also their ultimate overall effect on human health and the environment.
Abstract: A recent study by the Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS) shows that a broad range of chemicals found in residential, industrial, and agricultural wastewaters commonly occurs in mixtures at low concentrations downstream from areas of intense urbanization and animal production. The chemicals include human and veterinary drugs (including antibiotics), natural and synthetic hormones, detergent metabolites, plasticizers, insecticides, and fire retardants. One or more of these chemicals were found in 80 percent of the streams sampled. Half of the streams contained 7 or more of these chemicals, and about one-third of the streams contained 10 or more of these chemicals. This study is the first national-scale examination of these organic wastewater contaminants in streams and supports the USGS mission to assess the quantity and quality of the Nation's water resources. A more complete analysis of these and other emerging water-quality issues is ongoing.
Keywords:
pharmaceuticals;
hormones;
other wastewater contaminants;
steroids;
nonprescription drugs;
veterinary pharmaceuticals
2,153 citations
"Reactions of chlorine with inorgani..." refers background in this paper
...Although usually present in low concentrations (ng L 1-mg L 1), numerous of these compounds have been reported in groundwaters and surface waters (Blackburn and Waldock, 1995; Ternes, 1998; Hirsch et al., 1999; Kolpin et al., 2002; Ying et al., 2002)....
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