Diffusive phosphate transport in Al-rich acidic porous cation exchange system
Bibliographic record
Abstract
One-dimensional diffusive phosphate transport in a porous cation-exchange resin model system was investigated to examine the effect of exchangeable Al on the movement of phosphate. This study presumes that Al interacts with phosphate and H+ is produced as a result of deprotonation of H2PO4−. The production of H+ due to interactions between positively charged Al ions and phosphate ions was confirmed by measuring the pH change during the titration of phosphate by aluminum or aluminum by phosphate ions. A set of cylindrical wax columns packed with: (A) a mixture of sand and solid Al2O3, (B) a mixture of sand and Al3+-saturated cation-exchange resin, (C) a mixture of sand, solid Al2O3, and Al3+-saturated cation-exchange resin, and (D) sand as a control was used. A 0.2-g sample of 32P-KH2PO4 was applied on the surface of the mixture in each column simulating one-dimensional diffusion from an instantaneous planar source into a semi-finite system. Retardation of phosphate transport by exchangeable Al3+ was characterized by lowering of pH. Phosphate transport was not retarded in the presence of solid Al2O3 alone. Phosphate movement was further retarded in the presence of exchangeable Al3+ with solid Al2O3. Under this situation, H+ ion produced from precipitation reactions dissolved solid Al2O3, giving rise to more Al3+ in solution. Aluminum ion in the solution phase moved towards the site where phosphate was precipitated. From a mass balance of P, a slight amount of P was not recovered in the system whose pH was kept around 2.0 or below, indicating a probable formation of K-taranakite. Either K-taranakite or K2Al5H7(PO4)8−14H2O was identified as a final precipitation product from a series of titration experiments. However, at least two unidentified morphologically different amorphous aluminum phosphates were observed. Key words: Aluminum, cation-exchange, phosphate, precipitation, retardation, transport
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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".