Adsorption of single-ring model naphthenic acids on soils
Bibliographic record
Abstract
The adsorption of single-ring model naphthenic acids on soils was investigated using a batch partitioning method. The influence of the molecular structure of the sorbate, the organic carbon content of the sorbent, the temperature, the solution salt (calcium chloride) concentration, and the pH on the adsorption isotherms was determined. The adsorption coefficients (K d ) for two structurally related model naphthenic acids, 4-methycyclohexaneacetic acid (4MACH) and 4-methylcyclohexanecarboxylic acid (4MCCH), were 0.18 and 0.11 mL/g, respectively. The K d values determined for the individual cis and trans isomers were equal for a given model naphthenic acid within the experimental precision of the data. In contrast to reported differences observed for the biodegradation of geometric isomers of model naphthenic acids, the structure of the cis and trans isomers investigated had negligible effects on the measured adsorption isotherms. The adsorption coefficients of 4MACH for two soils with organic carbon contents of 1.6 and 2.7% were 0.18 and 0.22 mL/g, respectively. For the two temperatures studied, similar K d values were obtained for 4MACH (0.18 mL/g at 23°C and 0.21 mL/g at 4°C), indicating a predominantly physical adsorption process. Inorganic salt solutions of calcium chloride (CaCl 2 ) had significant effects on adsorption as the K d increased from 0.10 to 0.22 mL/g within the range of pore fluid chemistry investigated (0-30 mM CaCl 2 ). Likewise, the adsorption of 4MACH was significantly influenced by pH with the K d being 0.20, 0.18, and 0.11 mL/g in acidic (pH 2.9), neutral (pH 6.8), and alkaline solutions (pH 10), respectively. The low values of K d indicated that there would be little adsorption of the single-ring model naphthenic acids by soils. This will result in high partitioning to the water column in aquatic environments.Key words: model naphthenic acids, adsorption coefficients, soils, batch partitioning method.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".