Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes
In this study, batch experiments were carried out to investigate the effectiveness of persulfate (PS) as an oxidant agent to remediate benzene, toluene, ethylbenzene, and xylenes (BTEX) in saline environments and at high water temperatures (30 °C). This hydrological setting is quite common in contam...
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| Format: | Article |
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MDPI AG
2021-09-01
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| Series: | Hydrology |
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| Online Access: | https://www.mdpi.com/2306-5338/8/3/139 |
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| author | Waleed Saeed Orfan Shouakar-Stash Jim Barker Neil Thomson Rick McGregor |
| author_facet | Waleed Saeed Orfan Shouakar-Stash Jim Barker Neil Thomson Rick McGregor |
| author_sort | Waleed Saeed |
| collection | DOAJ |
| description | In this study, batch experiments were carried out to investigate the effectiveness of persulfate (PS) as an oxidant agent to remediate benzene, toluene, ethylbenzene, and xylenes (BTEX) in saline environments and at high water temperatures (30 °C). This hydrological setting is quite common in contaminated groundwater aquifers in Middle Eastern countries. In general, increasing the system temperature from 10 to 30 °C greatly enhanced the effectiveness of PS, and resulted in a faster oxidation rate for the target contaminants. When PS was added to the reactor at 30 °C, the targeted contaminants were almost completely oxidized over a 98-day reaction period. During the chemical oxidation of the BTEX, carbon and hydrogen isotope fractionations were monitored and utilized as potential proof of contaminant degradation. The calculated carbon-enrichment values were −1.9‰ for benzene, −1.5‰ for ethylbenzene and toluene, −0.4‰ for ρ,m-xylene, and −1.4‰ for o-xylene, while the hydrogen enrichment values were −9.5‰, −6.8‰, −2.1‰, −6.9‰, and −9.1‰, respectively. In comparison with other processes, the hydrogen and carbon isotope fractionations during the chemical oxidation by PS were smaller than the isotope fractionations resulting from sulfate reduction and denitrification. This observation demonstrates the differences in the transformation pathways and isotope fractionations when compounds undergo chemical oxidation or biodegradation. The distinct trend observed on the dual isotope plot (Δδ<sup>13</sup>C vs. Δδ<sup>2</sup>H) suggests that compound-specific isotope analysis can be utilized to monitor the chemical oxidation of BTEX by PS, and to distinguish treatment zones where PS and biodegradation technologies are applied simultaneously. |
| first_indexed | 2024-03-10T07:37:02Z |
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| issn | 2306-5338 |
| language | English |
| last_indexed | 2024-03-10T07:37:02Z |
| publishDate | 2021-09-01 |
| publisher | MDPI AG |
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| series | Hydrology |
| spelling | doaj.art-b665b4c89a794fb586d28e18995c38cb2023-11-22T13:22:54ZengMDPI AGHydrology2306-53382021-09-018313910.3390/hydrology8030139Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable IsotopesWaleed Saeed0Orfan Shouakar-Stash1Jim Barker2Neil Thomson3Rick McGregor4Department of Earth and Environmental Science, University of Waterloo, Waterloo, ON N2L 3G1, CanadaDepartment of Earth and Environmental Science, University of Waterloo, Waterloo, ON N2L 3G1, CanadaDepartment of Earth and Environmental Science, University of Waterloo, Waterloo, ON N2L 3G1, CanadaDepartment of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, CanadaIn-Situ Remediation Services Limited, St. George, ON N0E 1N0, CanadaIn this study, batch experiments were carried out to investigate the effectiveness of persulfate (PS) as an oxidant agent to remediate benzene, toluene, ethylbenzene, and xylenes (BTEX) in saline environments and at high water temperatures (30 °C). This hydrological setting is quite common in contaminated groundwater aquifers in Middle Eastern countries. In general, increasing the system temperature from 10 to 30 °C greatly enhanced the effectiveness of PS, and resulted in a faster oxidation rate for the target contaminants. When PS was added to the reactor at 30 °C, the targeted contaminants were almost completely oxidized over a 98-day reaction period. During the chemical oxidation of the BTEX, carbon and hydrogen isotope fractionations were monitored and utilized as potential proof of contaminant degradation. The calculated carbon-enrichment values were −1.9‰ for benzene, −1.5‰ for ethylbenzene and toluene, −0.4‰ for ρ,m-xylene, and −1.4‰ for o-xylene, while the hydrogen enrichment values were −9.5‰, −6.8‰, −2.1‰, −6.9‰, and −9.1‰, respectively. In comparison with other processes, the hydrogen and carbon isotope fractionations during the chemical oxidation by PS were smaller than the isotope fractionations resulting from sulfate reduction and denitrification. This observation demonstrates the differences in the transformation pathways and isotope fractionations when compounds undergo chemical oxidation or biodegradation. The distinct trend observed on the dual isotope plot (Δδ<sup>13</sup>C vs. Δδ<sup>2</sup>H) suggests that compound-specific isotope analysis can be utilized to monitor the chemical oxidation of BTEX by PS, and to distinguish treatment zones where PS and biodegradation technologies are applied simultaneously.https://www.mdpi.com/2306-5338/8/3/139chemical oxidationpersulfategasoline compoundsstable isotopes |
| spellingShingle | Waleed Saeed Orfan Shouakar-Stash Jim Barker Neil Thomson Rick McGregor Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes Hydrology chemical oxidation persulfate gasoline compounds stable isotopes |
| title | Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes |
| title_full | Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes |
| title_fullStr | Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes |
| title_full_unstemmed | Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes |
| title_short | Laboratory Experiments to Evaluate the Effectiveness of Persulfate to Oxidize BTEX in Saline Environment and at Elevated Temperature Using Stable Isotopes |
| title_sort | laboratory experiments to evaluate the effectiveness of persulfate to oxidize btex in saline environment and at elevated temperature using stable isotopes |
| topic | chemical oxidation persulfate gasoline compounds stable isotopes |
| url | https://www.mdpi.com/2306-5338/8/3/139 |
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