Effect of groundwater biogeochemistry on zero valent iron nanoparticles: Role of sulfidation and bacteria on reductive dechlorination
Notice bibliographique
Résumé
Accidental spills and past improper disposal practices of chlorinated solvents have led to widespread soil and groundwater contamination. Drinking water standards for trichloroethylene (TCE) and many other chlorinated organic contaminants are in the range of 5 µg/L and these compounds have received extensive regulatory attention because these compounds are often carcinogenic and neurotoxic. Direct injection of reactive nanoscale zerovalent iron particles (NZVI) is considered to be a promising approach for remediation of chlorinated compounds. NZVI is a strong reducing agent that can effectively transform TCE and other chlorinated organic compounds to non-toxic end products. The objective of the research was to assess various biogeochemical conditions on the reactivity of iron nanoparticles in particular sulfidation of NZVI for remediation of TCE. In addition, the feasibility of coupled NZVI-based remediation and bioremediation using polymer-coated bimetallic NZVI and a dechlorinating mixed culture consortia (KB-1) was investigated. We demonstrated that the extent of sulfidation of NZVI enhances the rate of dechlorination of TCE compared to non-sulfidated NZVI, and this enhancement depends on the Fe/S molar ratio of the sulfidated NZVI particles. Batch experiments where TCE was reacted with NZVI sulfidated to different extents (Fe/S molar ratios 0.62 to 66) showed that the surface-area normalized first-order TCE degradation rate constant increased 40 fold compared to non-sulfidated NZVI. FX-ray photoelectron spectroscopy analyses showed formation of a surface layer of FeS and FeS2. This indicates sulfide ions reacted with NZVI iron sulfide on surface of S-NZVI. We propose that more electrons are preferentially conducted from sulfidated NZVI than from unamended NZVI to TCE, likely because of greater binding affinity of TCE on the reactive sites of the iron sulfide outer layer. Aging of sulfidated iron nanoparticles (S-NZVI) and their influence on rate of TCE dechlorination was compared to the aged non-sulfidated NZVI. Long-term experiments indicate that pseudo-first order H2 evolution rate constant for non-sulfidated NZVI was 0.092 ± 0.005 d-1 and was significantly higher than the S-NZVI (Fe/S=25) at 0.051 ± 0.005 h-1. This difference in hydrogen evolved corresponds to the amount of reactive Fe(0) consumed in the absence of TCE. To further support, the efficacy of long-term reactivity S-NZVI batch TCE degradation experiment with anaerobically aged S-NZVI (40 days) degraded significantly more TCE than the non-sulfidated NZVI. Bimetallic, palladium-doped iron nanoparticles (Pd-NZVI) are capable of rapid transformation of higher initial TCE concentration, and the ability to form rapid H2 (electron donor for bacteria) may facilitate TCE biodegradation. Dehalococcoides are the only species of bacteria that are capable of degrading TCE completely to ethene under anaerobic conditions. Therefore, we investigated the interaction of carboxymethyl cellulose (CMC) stabilized palladium (Pd-NZVI) on the dechlorinating mixed culture KB-1 for reductive dechlorination of 1, 2 dichloroethane (DCA). Results suggest that systems with CMC alone as a sole carbon source and electron donor were capable of degrading 1, 2-DCA, and methane formation. The microcosms with KB-1 and polymer coated Pd-NZVI degraded 1, 2-DCA at a significantly higher rate constant compared to KB-1 and CMC systems. In addition, methanogenesis by KB-1 showed no statistically significant difference in the methane formation rate constants between Pd-CMC-NZVI and CMC only systems.Overall, this research demonstrates NZVI reactivity towards TCE and its longevity (efficacy) under anaerobic conditions can be enhanced with sulfidation. In addition, this research also shows that CMC stabilized bimetallic NZVI, is not inhibitory to Dehalococcoides spp. and could promote complete bioremediation.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».