Kinetic fractionation of antimony isotopes during reduction by sulfide

Veldhuizen, Hannah Juliette

Permalink

https://hdl.handle.net/2142/115586 Copy

Description

Title

Kinetic fractionation of antimony isotopes during reduction by sulfide

Author(s)

Veldhuizen, Hannah Juliette

Issue Date

2022-04-26

Director of Research (if dissertation) or Advisor (if thesis)

Johnson, Thomas M

Department of Study

Geology

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Antimony
• Isotope

Abstract

Antimony (Sb) is a toxic metalloid that enters the environment through both natural processes and anthropogenic input. Despite Sb’s increasing use, a limited number of studies exist on its mobility, toxicity, and geochemical reactions. Stable isotope ratios of elements in the environment can provide valuable information on sources and processes such as redox transformations, precipitation, and adsorption. Isotope ratio measurements can be used to determine the extent of reaction with better accuracy than concentration measurements and without complications caused by dilution and adsorption. However, this requires knowledge of the difference between the reactant and product isotope ratios, or fractionation factor, and laboratory studies are needed to determine fractionation factors for various relevant reactions at varying reaction conditions. Given that Sb isotopes have not been developed until recently, isotope fractionation factors for most processes of Sb are still unknown. Redox reactions are typically the most significant sources of isotopic fractionation in natural systems. The oxidation state of Sb in the environment influences it’s mobility, with Sb(III) being less mobile than Sb(V). To investigate the fractionation when Sb(V) (+5 valence) is chemically reduced by sulfide to Sb(III) (+3 valence), controlled experiments with 0.01 mM Sb(V) and 2 to 6 mM sulfide at a pH of 6 and 7 were performed. Anion exchange was used to separate Sb(V) from Sb(III), and isotope ratios were analyzed using hydride generation MC-ICP-MS. The fractionation (ε) values for pH 6/High H2S, pH 7/High H2S and pH 7/Low H2S were -0.45 ± 0.03 ‰, -0.36 ± 0.05 ‰, and -0.57 ± 0.03‰, respectively. This provides important fundamental knowledge of a major driver of Sb isotope variation in nature and will be used as Sb isotopes are developed for use in modern environmental monitoring efforts and as a proxy for paleo-redox conditions.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Hannah Veldhuizen

Owning Collections