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Title: Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species

Abstract

Arsenic occurs in the +III oxidation state as a metastable species in oxic waters. Under oxide conditions, As(III) is both more mobile in natural waters and less efficiently removed by water treatment processes than As(V). Other oxidants, however, can react with As(III) more rapidly than oxygen. The oxidation of As(III) by manganite occurs on the time scale of hours. Here, a method is introduced for the rapid determination of the total and dissolved concentrations of arsenic species in this heterogeneous system; absorbed arsenic concentrations are calculated by difference. The oxidation reaction is quenched by the addition of ascorbic acid to effect the reductive dissolution of manganite and concomitant release of adsorbed As(III) and As(V) into solution. Once in solution, As(III) and As(V) are separated using anion-exchange chromatography. Comparison of dissolved and total concentrations of As(III) and As(V) clearly illustrates that the overall conversion rate of As(III) to As(V) in this system would be overpredicted based solely on dissolved As(III) concentrations and underpredicted based solely on dissolved As(V) concentrations. The overall conversion of As(III) to As(V) was more rapid at pH 4 than at pH 6.3 and was unaffected by the presence of boric acid at 95 {micro}M or 3 mM.more » However, the presence of 200 {micro}M phosphate (at pH 4) decreased the overall rate of conversion of As(III) to As(V). Comparison of total and dissolved As(III) concentrations during the reaction time course demonstrates that the effects of pH and phosphate on adsorbed As(III) concentrations are generally consistent with these kinetic observations.« less

Authors:
;
Publication Date:
Research Org.:
Univ. of California, Los Angeles, CA (US)
OSTI Identifier:
20080465
Resource Type:
Journal Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 34; Journal Issue: 10; Other Information: PBD: 15 May 2000; Journal ID: ISSN 0013-936X
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; REMEDIAL ACTION; ARSENIC; ADSORPTION; OXIDATION; ENVIRONMENTAL TRANSPORT; WATER POLLUTION

Citation Formats

Chiu, V.Q., and Hering, J.G. Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species. United States: N. p., 2000. Web. doi:10.1021/es990788p.
Chiu, V.Q., & Hering, J.G. Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species. United States. doi:10.1021/es990788p.
Chiu, V.Q., and Hering, J.G. Mon . "Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species". United States. doi:10.1021/es990788p.
@article{osti_20080465,
title = {Arsenic adsorption and oxidation at manganite surfaces. 1. Method for simultaneous determination of adsorbed and dissolved arsenic species},
author = {Chiu, V.Q. and Hering, J.G.},
abstractNote = {Arsenic occurs in the +III oxidation state as a metastable species in oxic waters. Under oxide conditions, As(III) is both more mobile in natural waters and less efficiently removed by water treatment processes than As(V). Other oxidants, however, can react with As(III) more rapidly than oxygen. The oxidation of As(III) by manganite occurs on the time scale of hours. Here, a method is introduced for the rapid determination of the total and dissolved concentrations of arsenic species in this heterogeneous system; absorbed arsenic concentrations are calculated by difference. The oxidation reaction is quenched by the addition of ascorbic acid to effect the reductive dissolution of manganite and concomitant release of adsorbed As(III) and As(V) into solution. Once in solution, As(III) and As(V) are separated using anion-exchange chromatography. Comparison of dissolved and total concentrations of As(III) and As(V) clearly illustrates that the overall conversion rate of As(III) to As(V) in this system would be overpredicted based solely on dissolved As(III) concentrations and underpredicted based solely on dissolved As(V) concentrations. The overall conversion of As(III) to As(V) was more rapid at pH 4 than at pH 6.3 and was unaffected by the presence of boric acid at 95 {micro}M or 3 mM. However, the presence of 200 {micro}M phosphate (at pH 4) decreased the overall rate of conversion of As(III) to As(V). Comparison of total and dissolved As(III) concentrations during the reaction time course demonstrates that the effects of pH and phosphate on adsorbed As(III) concentrations are generally consistent with these kinetic observations.},
doi = {10.1021/es990788p},
journal = {Environmental Science and Technology},
issn = {0013-936X},
number = 10,
volume = 34,
place = {United States},
year = {2000},
month = {5}
}