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Please use this identifier to cite or link to this item: http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/7294

Title: Kinetics and mechanistic aspects of As(III) oxidation by aqueous chlorine, chloramines, and ozone: Relevance to drinking water treatment
Authors: Dodd, M.C.
N.D., Vu
Ammann, A.
V.C., Le
Kissner, R.
H.V., Pham
T.H., Cao
Berg, M.
Von Gunten, U.
Keywords: Concentration (process)
Ozone
Oxidation
pH effects
Water Purification
Water Supply
Hydrogen-Ion Concentration
Kinetics
pH measurement
stoichiometry
Issue Date: 2006
Publisher: Environmental Science and Technology
Citation: Volume: 40, Issue: 10, Page : 3285-3292
Abstract: Kinetics and mechanisms of As(III) oxidation by free available chlorine (FAC-the sum of HOCl and OCl-), ozone (O3), and monochloramine (NH2Cl) were investigated in buffered reagent solutions. Each reaction was found to be first order in oxidant and in As(III), with 1:1 stoichiometry. FAC-As(III) and O3- As(III) reactions were extremely fast, with pH-dependent, apparent second-order rate constants, k??app, of 2.6 (?0.1) ?? 105 M -1 s-1 and 1.5 (?0.1) ?? 106 M -1 s-1 at pH 7, whereas the NH2Cl-As(III) reaction was relatively slow (k??app = 4.3 (?1.7) ?? 10-1 M-1 s-1 at pH 7). Experiments conducted in real water samples spiked with 50 ?g/L As(III) (6.7 ?? 10 -7 M) showed that a 0.1 mg/L Cl2 (1.4 ?? 10 -6 M) dose as FAC was sufficient to achieve depletion of As(III) to <1 ?g/L As(III) within 10 s of oxidant addition to waters containing negligible NH3 concentrations and DOC concentrations <2 mg-C/L. Even in a water containing 1 mg-N/L (7.1 ?? 10-5 M) as NH 3, >75% As(III) oxidation could be achieved within 10 s of dosing 1-2 mg/L Cl2 (1.4-2.8 ?? 10-5 M) as FAC. As(III) residuals remaining in NH3-containing waters 10 s after dosing FAC were slowly oxidized (t1/2 ? 4 h) in the presence of NH 2Cl formed by the FAC-NH3 reaction. Ozonation was sufficient to yield >99% depletion of 50 ?g/L As(III) within 10 s of dosing 0.25 mg/L O3 (5.2 ?? 10-6 M) to real waters containing <2 mg-C/L of DOC, while 0.8 mg/L O3 (1.7 ?? 10-5 M) was sufficient for a water containing 5.4 mg-C/L of DOC. NH3 had negligible effect on the efficiency of As(III) oxidation by O3, due to the slow kinetics of the O3-NH3 reaction at circumneutral pH. Time-resolved measurements of As(III) loss during chlorination. ?? 2006 American Chemical Society.
URI: http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/7294
ISSN: 0013936X
Appears in Collections:2006-2008 VNU-DOI-Publications

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