Hydrogen Gas Production and Effects During Remediation Using Nano-scale Zero-valent Iron
Bibliographic record
Abstract
The objective of this study was to develop an understanding of the potential effects of hydrogen gas (H2) exsolution during nanoscale zero-valent iron (nZVI) groundwater remediation applications. An improved understanding of gas exsolution and its effects can be applied to remediation technologies that produce gas in excess of solubility limits, including bioremediation and nZVI. Experiments were performed in thin flow cells packed with water- saturated silica sands. Differential pressure measurements were taken under saturated conditions, after H2 gas exsolution and during gas dissolution. Images were processed with a quantitative light transmission technique to visualize and quantify gas production and transport, and to investigate flow diversion around the injection zone. In a larger-scale experiment, images were processed qualitatively to visualize gas production and transport, and to investigate flow diversion around the injection zone. Water samples were collected and analyzed for contaminant mobilization and redistribution to upper portions of the flow cell. The exsolution of H2 gas caused reductions in hydraulic conductivity with lower values associated with higher gas saturations. Images obtained from dye tests in all experiments demonstrated significant reduction in hydraulic conductivity due to H2 gas produced, with flow diversion of dye solution around the injection zone. The study demonstrated that the dissolution of exsolved gas can be used to investigate relative permeability at small saturation increments and at lower trapped gas saturations than can be obtained using external displacement experiments. H2 gas exsolved due to the reaction of nZVI with water was greater than the H2 gas produced by the self- hydrolysis of NaBH4 solution injected into saturated sands, despite using similar NaBH4 concentration as excess for nZVI synthesis. In the large-scale experiment, the exsolved H2 gas volume was sufficient to produce trapped gas in the injection area, and gas that travelled upwards and away from the injection area as gas channels. Vertical gas transport occurred above a high-concentration trichloroethene (TCE) plume, resulting in its redistribution of TCE, as well as ethene and ethane transport along the gas channel fronts.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".