Phosphorus Release from Calcium-Based Modified Sludge-Derived Biochar under Low-Molecular-Weight Organic Acids: Dual Role of Inorganic Anions
Bibliographic record
Abstract
Calcium-based substances carrying different inorganic anions will lead to the generation of different phosphorus (P) compounds in sludge pyrolysis products (biochar), which will inevitably affect P release efficiency. The effects of CaO and CaCl 2 (2.5%–20%) on P conversion during pyrolysis at 700 °C were studied. Simultaneously, the influence of three representative low-molecular-weight organic acids (LMWOAs: acetic acid (AA), oxalic acid (OA), and citric acid (CA)) on P release behavior was investigated. The results showed that when the addition amount of CaO and CaCl 2 was 10%, the AP concentration reached the maximum values of 47.05 and 46.98 mg/g, respectively. The main Ca–P of CaO-modified biochar was Ca 5 (PO 4 ) 3 OH, while CaCl 2 -modified biochar was mainly Ca–P (Ca 5 (PO 4 ) 3 Cl and Ca 2 PO 4 Cl) containing Cl. The P release rate of CaCl 2 -modified biochar in LMWOA was faster than that of CaO-modified biochar. Additionally, the order of P release efficiency in biochar is: CA > OA > AA at low concentrations (0.5 and 1.0 mM), OA > CA > AA at high concentrations (2.0 and 5.0 mM). The environmental factors affecting P release were ranked by significance: pH > organic matter concentration > temperature. Heavy metals showed minimal mobility during P release, confirming biochar’s stabilization capacity. Moreover, CaO-modified biochar has good stability and a slow P rate, while CaCl 2 -modified biochar could quickly address P deficiency and may be suitable for a severe P deficiency environment.
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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".