Rate-limited cation exchange in thin bentonitic barrier layers
Bibliographic record
Abstract
A three-compartment model was developed for simulating cation transport in bentonitic barrier layers that incorporates diffusion-controlled cation exchange among the mobile intergranular water (bulk pore water), immobile interparticle and interlayer water, and the montmorillonite mineral solid. Exchange on the external surfaces and interlayer region of montmorillonite is included. The model was evaluated for divalent-for-monovalent cation exchange in bentonite with experiments. A parametric study was conducted using the model to investigate factors affecting the time required to establish chemical equilibrium (i.e., completion of cation exchange) between the permeant liquid and thin layers of bentonite simulating geosynthetic clay liners (GCLs). Predictions obtained with the model were in general agreement with the data without calibration, except for Na concentrations in the effluent at very long times. Parametric simulations conducted with the model show that the time required to establish chemical equilibrium in GCLs is affected by the rate at which adsorbing cations are delivered to the pore space (affected by seepage velocity or influent concentration), the rate of mass transfer between the mobile and immobile liquid phases (controlled primarily by granule size of the bentonite), and the number of sites available for sorption (controlled by CEC and the dry density of the bentonite).Key words: bentonite, montmorillonite, exchange complex, diffusion, immobile liquid, interlayer.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.004 | 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 teacher head, 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".