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Preservation of sulfidic waters containing dissolved As( iii )

Preservation of sulfidic waters containing dissolved As( iii ) Solutions containing variable concentrations of sulfide (0 to 31 ppm) and arsenite (0.35 to 10 ppm) were subjected to several different preservation treatments. As predicted by equilibrium thermodynamics, at near-neutral pH the experimental solutions were undersaturated with respect to orpiment (As 2 S 3 ). However, upon acidification to pH 2 with HCl or HNO 3 , instantaneous precipitation of poorly crystalline As 2 S 3 occurred in sulfidic solutions which resulted in the loss of dissolved arsenite. These results have implications concerning the practice of acidifying water samples containing hydrogen sulfide with HCl or HNO 3 for the purpose of preserving total arsenic values. If a near-neutral water sample contains 1 ppm arsenite and as little as 0.4 ppm sulfide, loss of dissolved arsenic will occur upon acidification. An alternative three-step preservation method involving base addition, oxidation, and acidification is proposed and investigated as an appropriate technique for preserving sulfide-bearing aqueous samples for total arsenic. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Environmental Monitoring Royal Society of Chemistry

Preservation of sulfidic waters containing dissolved As( iii )

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Publisher
Royal Society of Chemistry
Copyright
This journal is © The Royal Society of Chemistry
ISSN
1464-0325
eISSN
1464-0333
DOI
10.1039/b306567g
Publisher site
See Article on Publisher Site

Abstract

Solutions containing variable concentrations of sulfide (0 to 31 ppm) and arsenite (0.35 to 10 ppm) were subjected to several different preservation treatments. As predicted by equilibrium thermodynamics, at near-neutral pH the experimental solutions were undersaturated with respect to orpiment (As 2 S 3 ). However, upon acidification to pH 2 with HCl or HNO 3 , instantaneous precipitation of poorly crystalline As 2 S 3 occurred in sulfidic solutions which resulted in the loss of dissolved arsenite. These results have implications concerning the practice of acidifying water samples containing hydrogen sulfide with HCl or HNO 3 for the purpose of preserving total arsenic values. If a near-neutral water sample contains 1 ppm arsenite and as little as 0.4 ppm sulfide, loss of dissolved arsenic will occur upon acidification. An alternative three-step preservation method involving base addition, oxidation, and acidification is proposed and investigated as an appropriate technique for preserving sulfide-bearing aqueous samples for total arsenic.

Journal

Journal of Environmental MonitoringRoyal Society of Chemistry

Published: Oct 16, 2003

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