Full Description

Pre-oxidation of arsenite (As(III)) to arsenate (As(V)) is commonly recommendedas a means of improving arsenic removal during physicochemical drinking water treatmentprocesses. However, oxidant-scavenging matrix constituents such as dissolved organic matter(DOM) and NHsub3/sub/NHsub4/subsup+/supwhich can be present at high concentrations within reduced, As(III)-laden groundwaters (2-4) may impair As(III) oxidation efficiency by competing with As(III) foravailable oxidant. Quantitative knowledge of the rate constants and mechanisms governingoxidation of As(III) by common drinking water oxidants would greatly facilitate modeling andoptimization of As(III) oxidation processes for treatment of such waters.In the present investigation, apparent second-order rate constants, k"subapp/sub,were measured foroxidation of As(III) by free available chlorine (FAC - representing bulk HOCl/OClsup-/sup), NHsub2/subCl, andOsub3/sub within the pH range 2 to 11, to permit evaluation of pH-dependencies for each reaction.Stoichiometries and reaction orders were also measured, to facilitate identification of oxidationmechanisms. Additional experiments were conducted in water samples collected from LakeZurich, in Switzerland, and from two groundwater treatment facilities in Hanoi, Vietnam, toquantify matrix effects on As(III) oxidation efficiency, and to test the suitability of measured rateconstants for modeling As(III) oxidation in real waters. Includes 10 references, tables, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 8File Size: 1 file , 570 KB