Abstract
Particulate HgS is generally thought to be the most abundant Hg
species in stored petroleum hydrocarbons stocked on-shore. It is also assumed that due to its high stability constant, HgS is chemically inert. However, results from the current study would suggest otherwise. Firstly, a comparison study of the analytical performance of ICP-MS and CV-AFS with respect to matrix effect, showed no significant difference in the measured Hg concentrations in studied samples when CV-AFS is used in the alkali mode. Subsequently, the suitability of three quantification methods during Hg speciation was investigated. Both external calibration and standard addition methods resulted troublesome with the former showing matrix dependence and the latter being hindered by the formation of an emulsion during the derivatisation step. Results from species-specific isotope dilution (SS-ID-GC-ICP-MS), on the other hand, performed at different equilibration times, showed a random variation in the calculated Hg2+ concentration (RSD 32%), 2 suggesting that factors independent of equilibration time cause the observed variation. Further sedimentation of Hg particulate by means of ultracentrifugation improved the precision of SS-ID-GC-ICP-MS by 10-fold. These results would suggest that Hg particles in petroleum products are reactive at low temperature during Grignard alkylation.
species in stored petroleum hydrocarbons stocked on-shore. It is also assumed that due to its high stability constant, HgS is chemically inert. However, results from the current study would suggest otherwise. Firstly, a comparison study of the analytical performance of ICP-MS and CV-AFS with respect to matrix effect, showed no significant difference in the measured Hg concentrations in studied samples when CV-AFS is used in the alkali mode. Subsequently, the suitability of three quantification methods during Hg speciation was investigated. Both external calibration and standard addition methods resulted troublesome with the former showing matrix dependence and the latter being hindered by the formation of an emulsion during the derivatisation step. Results from species-specific isotope dilution (SS-ID-GC-ICP-MS), on the other hand, performed at different equilibration times, showed a random variation in the calculated Hg2+ concentration (RSD 32%), 2 suggesting that factors independent of equilibration time cause the observed variation. Further sedimentation of Hg particulate by means of ultracentrifugation improved the precision of SS-ID-GC-ICP-MS by 10-fold. These results would suggest that Hg particles in petroleum products are reactive at low temperature during Grignard alkylation.
| Original language | English |
|---|---|
| Pages (from-to) | 130-137 |
| Number of pages | 8 |
| Journal | Energy & Fuels |
| Volume | 30 |
| Issue number | 1 |
| Early online date | 30 Nov 2015 |
| DOIs | |
| Publication status | Published - 21 Jan 2016 |
Bibliographical note
AcknowledgmentMohammed M. Lawan, David J. Bellis, Andrea Raab, and Dagmar S. Urgast are thanked for all of their advice on ICP-MS, which has helped to achieve this work. Graeme Nicol is thanked for his help with ultracentrifuge. John Alvarez, Dennis O’Rear, and Sheila Yeh (Chevron, ETC, U.S.) are acknowledged for their valuable comments and fruitful discussion. Z.G. thanks Chevron, U.S., and the College of Physical Sciences at University of Aberdeen for the provided studentship.