Photolysis of aqueous free chlorine species (NOCI and OCI-) with 254 nm ultraviolet light

University of Alberta, Edmonton, Alberta, Canada
Journal of Environmental Engineering and Science (Impact Factor: 0.67). 05/2007; 6(3):277-284. DOI: 10.1139/S06-052

ABSTRACT The quantum yields of the UV photolysis of free chlorine (OCl− and HOCl) at 254 nm were measured in a series of batch reactor experiments from pH 5 to 10 and at various concentrations. When the concentration of free chlorine is low (3.5 mg Cl/L) to moderate (70 mg Cl/L), the quantum yields of HOCl and OCl− are 1.0 ± 0.1 and 0.9 ± 0.1, respectively. When the concentration increases to higher levels (>70 mg Cl/L), the quantum yield of HOCl photolysis increases significantly, whereas the quantum yield of OCl − photolysis is essentially independent of concentration. In addition, based on the experimental results obtained in this research, a mathematic model was developed that can be used for the prediction of the quantum yield for the UV photolysis of free chlorine at 254 nm. The quantum yields predicted by this model agree very well with the measured data. Also, the dependence of free chlorine decomposition on the fluence (UV dose) and the effect of water quality on the quantum yield of free chlorine species were investigated in this research.

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    • ". Time profiles of MPT byproducts in (a) deionized water, (b) surface water, (c) tap water, and (d) filtered water during the UV/chlorination reaction (experimental conditions; [MTP]0 = 100 ng/L, [Cl2] = 5 mg/L, UV–C intensity = 4.4 mW/cm 2 , pH 7, 20 • C). (Fig. 4(d)). Feng et al. [28] proposed two chain reactions related to DOM in water by OH and Cl radicals during the UV/chlorination reaction (Eqs. (14)–(17)). "
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    ABSTRACT: Metoprolol (MTP), a hypertension depressor, has been increasingly detected even after conventional water treatment processes. In this study, the removal of MTP was compared using chlorination (Cl2), UV-C photolysis, and UV/chlorination (Cl2/UV) reactions. The results showed that the UV/chlorination reaction was most effective for MTP removal. MTP removal during UV/chlorination reaction was optimized under various conditions of UV intensity (1.1-4.4mW/cm(2)), chlorine dose (1-5mg/L as Cl2), pH (2-9), and dissolved organic matter (DOM, 1-4mgC/L) using a two-level factorial design with 16 experimental combinations of the four factors. Among the factors examined, DOM scavenging by OH radicals was the most dominant in terms of MTP removal during UV/chlorination reaction. The established model fit well with the experimental results using to various water samples including surface waters, filtered and tap water samples. The optimized conditions (UV intensity=4.4mW/cm(2), [Cl2]=5mg/L, pH 7, and [DOM]=0.8-1.1mgC/L) of the model removed more than 78.9% of MTP for filtered water samples during UV/chlorination reaction. Using LC-MS/MS, five byproducts of MTP (molecular weight: 171, 211, 309, 313, and 341, respectively) were identified during UV/chlorination reaction. Based on this information, the MTP transformation mechanism during UV/chlorination was suggested. Our results imply that applying UV/chlorination process after filtration stage in the water treatment plant (WTP) would be the most appropriate for effective removal of MTP. Copyright © 2014 Elsevier B.V. All rights reserved.
    Journal of Hazardous Materials 12/2014; 285C:453-463. DOI:10.1016/j.jhazmat.2014.11.052 · 4.53 Impact Factor
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    • "), when electrolysis are carried out at chloride 51 containing medium at specific pH conditions. Moreover, the 52 combination of the chloro oxidant species generation and UV 53 irradiation can also result in the formation high reactive species 54 [13]. The possible generation of organochlorine byproducts is the 55 main drawback; however, as showed by Malpass et al. [14], no 56 toxicity was observed in samples of the herbicide Atrazine treated 57 with the photo-assisted electrochemical method using a DSA 1 58 electrode at chloride or sulfate containing media. "
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    ABSTRACT: Phthalic acid esters are synthetic compounds used as additives in plastic structures. As these chemicals are physically bound, they can contaminate humans affecting the endocrine system. The present study focused on the photo-assisted electrochemical (PAE) method to degrade a phthalic acid ester, such as dimethyl phthalate–DMP, using a one-compartment filter press flow cell and a commercial DSA® electrode. The variables investigated to optimize the DMP compound removal were NaCl concentration, current density, and temperature. The efficiency towards the DMP concentration abatement and total organic carbon (TOC) removal were the analytical parameters analyzed. The highest rates of DMP and TOC removals were attained at high NaCl concentrations and current densities, due to the generation of high reactive oxidants in the PAE method that seemed to suppress mass transport limitations. The temperature had no significant influence on the DMP removal. Moreover, depending on the nature of the intermediate compounds generated, the PAE method could enable a rapid treatment option before disposal of contaminated effluents containing DMP, and possibly other endocrine disruptors. Despite the high levels of current efficiency attained, more work is required to optimize the electrical energy consumption, especially with respect to the choice of the UV lamp.
    Journal of Environmental Chemical Engineering 06/2014; 2(2). DOI:10.1016/j.jece.2014.02.003
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    • "Free chlorine photolysis in the UV photoreactor [30]. "
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    Chemical Engineering Journal 03/2014; 240:235–243. DOI:10.1016/j.cej.2013.11.087 · 4.32 Impact Factor
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