Rates of elemental sulphur oxidation and associated oxygen and sulphur isotope fractionation
Smith, Laura Ann
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¡ãC) 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¡ãC) to 0.98 (32¡ãC) ¦Ìg S0 cm-2 d-1 (Q10 ¡Ö 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 ¦Ìg S0 cm-2 d-1) between 12 and 32¡ãC. 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 ¦Ä18O(SO4) generally reflected the ¦Ä18O(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 ¦Ä18O(SO4) can also be used to track water movement through the block.
DegreeMaster of Science (M.Sc.)
CommitteeWassenaar, Len; Ansdell, Kevin; Farrell, Richard
Copyright DateJuly 2009