Rates of elemental sulphur oxidation and associated oxygen and sulphur isotope fractionation
Date
2009-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
Elemental sulphur (S⁰) is removed from sour gas deposits (high H₂S) during refinement. The resulting S⁰ is often stored onsite when the costs of shipping S⁰ to market exceeds the costs of storing it in large above ground blocks. With the aid of acidiphilic bacteria, atmospheric air and water oxidize S⁰ to sulphate (SO₄²⁻). Long term storage is under consideration; however, oxidation rates and the role of each oxygen source (O₂(g) and H₂O) is not clear.
S⁰ oxidation experiments were conducted over a range of temperatures (6-32°C) to investigate reaction rates and isotopic fractionation of O and S isotopes during oxidation. The experiments also investigated the effect of integrating S⁰ oxidizing microorganisms and available nutrients on both the reaction rates and isotope fractionation. Results indicated > 95% of total SO₄²⁻ generated can be attributed to autotrophic microbial activity. Experiments conducted in a nutrient rich mineral solution showed rates increase with temperature from 0.16 (6°C) to 0.98 (32°C) μg S⁰ cm⁻² d⁻¹ (Q₁₀ ≈ 1.7 - 1.9). Experiments conducted in a nutrient poor solution (deionized water) showed oxidation rates did not increase with temperature (0.06 to 0.08 μg S⁰ cm⁻² d⁻¹) between 12 and 32°C. Oxygen isotope analysis of the generated SO₄²⁻ indicated essentially all oxygen incorporated into the SO₄²⁻ originated from H₂O. In addition, effluent samples obtained from S⁰ block effluent at SCL indicated δ¹⁸O(SO₄) generally reflected the δ¹⁸O(H₂O) in the system at the time of oxidation. While covering the S⁰ blocks with an impermeable cover would undoubtedly minimize total SO₄²⁻ accumulation in block effluent, the results of this study suggest δ¹⁸O(SO₄) can also be used to track water movement through the block.
Description
Keywords
sulphuric acid, storage blocks, oil sands, sour gas
Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geological Sciences