Showing papers on "Chlorine published in 2015"
TL;DR: Almost complete mineralization of effluent organic matter and trace contaminants can be obtained by this anodic oxidation with a boron-doped diamond anode for the treatment of secondary effluent from a municipal sewage treatment plant containing 29 target pharmaceuticals and pesticides.
225 citations
TL;DR: With the data set from this study, the ratio between the species-specific rate constants for the reactions of chlorine versus bromine with phenolic compounds was confirmed to be about 3000, showing that for natural organic matter samples, oxidation (ET) is far more important than bromines incorporation (EAS).
222 citations
01 Jan 2015
TL;DR: In this article, the selectivity between oxygen and chlorine evolution in the chlor-alkali and chlorate processes was studied and a comprehensive review of the results can be found in Table 1.
Abstract: Selectivity between oxygen and chlorine evolution in the chlor-alkali and chlorate processes : a comprehensive review
186 citations
TL;DR: In this paper, the chemical linkage of neutral hydrophilic polymer polyvinyl alcohol (PVA) on the surface of a commercial aromatic polyamide (PA) thin-film composite (TFC) reverse osmosis membrane is reported.
152 citations
TL;DR: The results indicate that the UV/chlorine process could represent an alternative to conventional breakpoint chlorination for ammonia-containing water, with several advantages in terms of simplicity, short reaction time, and reduced chemical dosage.
142 citations
TL;DR: The results provide strong evidence that hydrothermal carbonization of household organic wastes which can be tied to co-discarded PVC-plastic residues is environmentally sound regarding the formation of toxic organic products.
124 citations
TL;DR: DBP formation potential for THMs, HAAs, HANs, and AOX was observed to increase approximately to the same extent as was observed for pretreatment using the more common AOP of UV combined with hydrogen peroxide (UV/H2O2).
120 citations
01 Jan 2015
TL;DR: In this article, the second-order rate constants for metronidazole (MDZ), nalidixic acid (NDA), diethyltoluamide (DEET) and caffeine (CAF) were investigated by the UV/chlorine process.
Abstract: The UV/chlorine process is an emerging advanced oxidation process (AOP) that produces various reactive species, such as hydroxyl radicals (HO) and reactive chlorine species (RCS). The effects of the treatment conditions, such as chlorine dosage and pH, and the water matrix components of natural organic matter (NOM), alkalinity, ammonia and halides, on the kinetics and reactive species in the degradation of four micropollutants, metronidazole (MDZ), nalidixic acid (NDA), diethyltoluamide (DEET) and caffeine (CAF), by the UV/chlorine process were investigated. The degradation of MDZ and CAF was primarily attributable to HO and ClO, respectively, while that of NDA was primarily attributable to both ClO and CO3-. HO, Cl and CO3- are important for the degradation of DEET. The second-order rate constants for ClO with CAF and CO3- with NDA were determined to be 5.1 (±0.2) × 107 M-1s-1 and 1.4 (±0.1) × 107 M-1s-1, respectively. Increasing chlorine dosage slightly changed the contribution of HO but linearly increased that of ClO to micropollutant degradation. Increasing pH decreased the contribution of either HO or Cl but not that of ClO. Both NOM and bicarbonate decreased the contributions of HO and Cl, whereas NOM but not bicarbonate significantly decreased that of ClO. The contribution of either HO or Cl first rose and then fell as the molar ratio of ammonia to chlorine increased from 0 to 1:1, while that of ClO decreased. The co-presence of high concentrations of Cl- and Br- enhanced the contribution of ClBr- and BrCl.
118 citations
TL;DR: In this article, the authors show that perchlorate (ClO4−) and ClO3− can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions.
Abstract: Perchlorate (ClO4−) has been detected on Mars, but its production and distribution are unclear. Mechanisms requiring atmospheric chlorine are insufficient for measured concentrations. We conducted studies under Mars conditions using halite (NaCl) alone, soil simulants consisting of silica (SiO2), Fe2O3, Al2O3, and TiO2. After 170 h irradiation, samples analyzed by ion chromatography (IC) showed ClO4− and ClO3− present in all samples. When SiO2 was added, yield increased from 2 to 42 nmol and 0.4 to 2.6 nmol, respectively. We attribute this to SiO2 and metal oxides acting as photocatalysts, generating O2− radicals from O2 which react with chloride. Results show ClO4− and ClO3− can be produced photochemically on Cl minerals without atmospheric chlorine or aqueous conditions, and explain high concentration of ClO4− and ClO4−/Cl− ratios detected by Phoenix. They provide evidence that its distribution on Mars is dictated by distribution of chlorine and provide insight into the oxidizing nature of the soil and its potential effects on organics.
114 citations
TL;DR: In this article, the chemiluminescence (CL) reaction with hypochlorite was studied and the effect of radical scavengers on the reaction was studied, and the method was successfully applied to the determination of free chlorine in (spiked) samples of tap water and pool water.
Abstract: Graphene quantum dots (GQDs) were prepared by a new and facile procedure, and their chemiluminescence (CL) reaction with hypochlorite was studied. It was found that hypochlorite can directly oxidize GQDs to give rise to CL emission, and that the surfactant cetyl trimethyl ammonium bromide enhances CL by a factor of about 18. CL and fluorescence spectra were acquired, and the effect of radical scavengers on the reaction was studied. This CL system was used to develop a simple and sensitive method for the determination of hypochlorite in the 0.5 μM to 1.0 mM concentration range, with a detection limit of 0.3 μM. The method was successfully applied to the determination of free chlorine in (spiked) samples of tap water and pool water.
108 citations
TL;DR: In this article, the mechanism of electrochemical (EC) oxidative degradation of p-nitrophenol (PNP) by ruthenium oxide coated titanium (Ti/RuO2) electrode was investigated.
TL;DR: In this paper, the effects of oxidation with sodium hypochlorite at different concentrations of active chlorine (0.5, 1.0 and 1.5 ) on physicochemical, morphological, pasting, thermal and gel texture properties of potato starch were evaluated.
Abstract: The objective of this study was to evaluate the effects of oxidation with sodium hypochlorite at different concentrations of active chlorine (0.5, 1.0 and 1.5 g/100 g) on the physicochemical, morphological, pasting, thermal and gel texture properties of potato starch. The native and oxidized starches were used in different concentrations (3.0, 4.0 and 5.0 g starch/100 mL) for the preparation of biodegradable films using glycerol as plasticizer. The films were evaluated for their mechanical properties, color, water solubility and permeability of water vapor. The degree of oxidation potato starches was more intense as there was an increased concentration of active chlorine in the reaction. Films made with oxidized starch with the highest level of active chlorine had lower tensile strength when compared to native starch films. Also, these films had a lower water solubility and water vapor permeability as compared to the native starch films.
TL;DR: In this paper, a linear relationship between the decreased fluorescence intensity of N,S-CDs and the concentration of free chlorine in the range from 0.01 to 100μM was obtained with a detection limit of 5 nM (3σ).
Abstract: Nitrogen and sulfur co-doped carbon dots (N,S-CDs) emitted strong blue fluorescence in aqueous solution, and it was found that the free chlorine could efficiently quench the fluorescence of the N,S-CDs, which was utilized as a sensitive, low-cost and green fluorescence probe for the detection of free chlorine. Under optimal conditions, a linear relationship between the decreased fluorescence intensity of N,S-CDs and the concentration of free chlorine in the range from 0.01 to 100 μM was obtained with a detection limit of 5 nM (3σ). The proposed method was successfully applied for the determination of free residual chlorine in tap water and swimming pool with quantitative recovery (91–106%). The developed N,S-CDs fluorescence probe provides a new and promising tool for the water quality monitoring in the environmental analysis fields with low cost and excellent performance.
TL;DR: Electrochemical water disinfection represents a suitable and efficient process for producing pathogen-free water without the use of any chemicals.
TL;DR: It is concluded that direct ammonia oxidation on graphite electrodes is a treatment option for source-separated urine with three major advantages: the formation of chlorinated by-products is prevented, less energy is consumed than in indirect ammonia oxidation and readily available and cheap graphite can be used as the electrode material.
TL;DR: A post-treatment of the liquid as well as the gas phase should be foreseen if CBP formation cannot be prevented by eliminating chloride or organic substances in a pretreatment.
Abstract: Chlorination byproducts (CBPs) are harmful to human health and the environment Their formation in chlorine mediated electro-oxidation is a concern for electrochemical urine treatment We investigated the formation of chlorate, perchlorate, and organic chlorination byproducts (OCBPs) during galvanostatic (10, 15, 20 mA·cm–2) electro-oxidation of urine on boron-doped diamond (BDD) and thermally decomposed iridium oxide film (TDIROF) anodes In the beginning of the batch experiments, the production of perchlorate was prevented by competing active chlorine and chlorate formation as well as by direct oxidation of organic substances Perchlorate was only formed at higher specific charges (>17 Ah·L–1 on BDD and >29 Ah·L–1 on TDIROF) resulting in chlorate and perchlorate being the dominant CBPs (>90% of initial chloride) BDD produced mainly short chained OCBPs (dichloromethane, trichloromethane, and tetrachloromethane), whereas longer chained OCBPs (1,2-dichloropropane and 1,2-dichloroethane) were more frequent
TL;DR: It is reported here that the complex ions AgCl2(-) and AgCl3(2-) form in concentrated Cl(-) solutions, avoiding AgCl precipitation and providing access to the higher oxidation states by delocalizing the oxidative charge over theCl(-) ligands.
Abstract: Chloride oxidation to chlorine is a potential alternative to water oxidation to oxygen as a solar fuels half-reaction. Ag(I) is potentially an oxidative catalyst but is inhibited by the high potentials for accessing the Ag(II/I) and Ag(III/II) couples. We report here that the complex ions AgCl2– and AgCl32– form in concentrated Cl– solutions, avoiding AgCl precipitation and providing access to the higher oxidation states by delocalizing the oxidative charge over the Cl– ligands. Catalysis is homogeneous and occurs at high rates and low overpotentials (10 mV at the onset) with μM Ag(I). Catalysis is enhanced in D2O as solvent, with a significant H2O/D2O inverse kinetic isotope effect of 0.25. The results of computational studies suggest that Cl– oxidation occurs by 1e– oxidation of AgCl32– to AgCl3– at a decreased potential, followed by Cl– coordination, presumably to form AgCl42– as an intermediate. Adding a second Cl– results in “redox potential leveling”, with further oxidation to {AgCl2(Cl2)}− followed...
TL;DR: The possibility of simultaneous removal of low-concentration organic pollutants and some inorganic salts by combining electrochemical oxidation and electrosorption was investigated and provides a new strategy for wastewater treatment and recycling.
TL;DR: In this article, regiodivergent C-H direct chlorination on 8-acylaminoquinolines could be realized by using N-chlorosuccinimide (NCS) as a source.
TL;DR: In this article, the advantages and limitations of electrolyzed water, particularly regarding the organic matter content, are discussed and compared to the use of hypochlorite, and a new electrochemical process using boron-doped diamond electrodes can generate additional reactive oxidant species than chlorine.
Abstract: Water disinfection is one of the most critical processing steps in fresh-cut vegetable production. Technologies capable for the efficient disinfection of process water and recycled water would allow reducing wastewater and have less impact on the environment. Among the chemical disinfectants, hypochlorite solutions are still the most widely used. Electrochemical disinfection of the wash water has been demonstrated to be effective in eliminating a wide spectrum of pathogens in process water. Both hypochlorite solutions and electrochemically produced chlorine compounds, in particular hypochlorous acid, are effective disinfectants when adequate doses are used. A new electrochemical process using boron-doped diamond electrodes can generate additional reactive oxidant species than chlorine and further enhance the disinfecting capacity. However, there are pros and cons on the use of one or other disinfectant agents. In this review, the technological advantages and the limitations of electrolyzed water, particularly regarding the organic matter content, are discussed and compared to the use of hypochlorite.
TL;DR: In this article, a low-cost, reliable and sensitive electrochemical method for free chlorine analysis in water using inkjet printed silver electrodes is presented, based on linear sweep voltammetry (LSV) analysis of AgCl/Ag2O films formed over an ink jet printed silver electrode by the spontaneous reaction between silver and free chlorine species (i.e. HClO and ClO−) present in solution.
TL;DR: Among the six investigated I-THMs, iodoform was the major species formed during the oxidation using chlorine, ClO₂ and KMnO⁂, and Iodide contributed to I- THM formation much more significantly than bromide.
TL;DR: Increases in both FDOM intensity and FI are viable qualitative indicators of IOM release in natural waters and following oxidation and may provide a more robust real-time indication of the presence of Iom than conventional dissolved organic carbon or UV absorbance measurements.
TL;DR: In this paper, the authors examined which DSA electrode, RuO2 or IrO2, is more effective for chlorine evolution with the same moles of Ru or Ir deposited on the surface of each electrode using the thermal decomposition method.
TL;DR: In this article, the authors compared the effect of citric acid and chlorine dioxide in trichloromethane formation and determined trichchloromethanes levels in chlorinated wash water, cut-lettuce and diced onions.
TL;DR: In this article, the performance of titania supported nickel catalyst (Ni/TiO 2 ) with pre-treatments for the selective methanation of CO (CO-SMET) in reformate gas has been studied to elucidate the role of chlorine component in the meetinghanation activity and CO/CO 2 reaction selectivity in COSMET.
Abstract: Catalytic performance of titania supported nickel catalyst (Ni/TiO 2 ) with pre-treatments for the selective methanation of CO (CO-SMET) in reformate gas has been studied to elucidate the role of chlorine component in the methanation activity and CO/CO 2 reaction selectivity in CO-SMET. Raw commercial TiO 2 , used as the support material, contains a certain amount of chlorine component, and the chlorine component can be removed by the heat treatment in air and water washing treatment. The Ni/TiO 2 catalyst prepared from the TiO 2 containing chlorine component exhibited high CO/CO 2 reaction selectivity, that is, low CO 2 methanation activity due to its low reverse water gas shift (r-WGS) activity, while the catalysts containing no chlorine component displayed quite low selectivity. The evaluation of the activity of the Ni/TiO 2 catalysts prepared from the starting Ni salts with different mixing molar ratios of Ni chloride and Ni nitrate indicates that a trace amount of chlorine led to the improved CO/CO 2 reaction selectivity in CO-SMET. The chlorine component in the Ni/TiO 2 catalysts is considered to be located on the interface of the Ni particles and the TiO 2 support, giving rise to the suppression of CO 2 methanation via the r-WGS step.
TL;DR: This work presents the reactivity and photochemistry of 2,5-diphenyltellurophene, the first example of photodefluorination from a tellurium compound, and demonstrates Photoreductive halogen elimination and photodebromination.
Abstract: We present the reactivity and photochemistry of 2,5-diphenyltellurophene. A change in oxidation state from Te(II) to Te(IV) occurs by oxidative addition of bromine, chlorine, and fluorine from appropriate halogen sources. Photoreductive halogen elimination is demonstrated using optical absorption spectroscopy and NMR spectroscopy. The photodebromination reaction occurs with 16.9% quantum yield, the highest value for any Te compound. Photoreductive elimination of chlorine and fluorine occurs with quantum yields of 1.6% and 2.3%, respectively, albeit with less efficient halogen trapping when an organic trap is used. Improved fluorine trapping was achieved using water, allowing for much cleaner photodefluorination. This is the first example of photodefluorination from a tellurium compound.
TL;DR: In this article, the authors correlate the evolution of membrane characteristics due to contact with hypochlorite used as cleaning agent to its selectivity towards model solutes, and demonstrate that hypoxylite induced membrane degradation, on one hand modified the solutes-membrane interactions increasing irreversible fouling and, on the other hand, lowered the selectivity.
TL;DR: In this article, the authors investigated how the survival of human pathogens was affected by the dynamic changes in water quality during chlorine depletion and replenishment in simulated produce washing operations and provided quantitative data needed by the fresh-cut produce industry and the regulatory agencies to establish critical operational control parameters to prevent pathogen survival and cross-contamination.