Understanding the Interaction Mechanism between Elemental Selenium and Ferric Hydroxide in Wastewater Treatment
Bibliographic record
Abstract
The conversion of selenium oxyanions to elemental selenium (Se 0 ) of low solubility and bioavailability is an effective industrial approach for selenium management in wastewater treatment. The generated Se 0 particles require further treatment with coagulants such as ferric ions to facilitate the precipitation of Se 0 particles. In this work, the settling of Se 0 particles in simulated wastewater was investigated with amorphous ferric hydroxide (Fe(OH) 3 ) as a coagulant prepared from hydrolysis of ferric chloride. The effects of ferric ion dosage, water composition, and pH on the Se 0 removal percentage were investigated. The surface properties, i.e., ζ potential and morphology, were characterized, which influenced the interactions between Se 0 and Fe(OH) 3 . The forces acting between Se 0 and Fe(OH) 3 surfaces were directly measured, for the first time, using atomic force microscopy (AFM). The water composition and pH had a significant effect on the adhesion force. In simulated wastewater, the adhesion force generally increased with pH, suggesting that the adsorption of Ca 2+ and Mg 2+ on Fe(OH) 3 surface increased with pH, which enhanced the adhesion. Interestingly, long-range pull-off forces and sawtooth patterns were observed on the retraction force–separation curves, which were attributed to the stretching of Fe(OH) 3 particle aggregates or chains during separation. Bulk settling tests showed that the best Se 0 removal performance of Fe(OH) 3 was found to be around pH 8, which was because the largest amount of Fe(OH) 3 precipitates was found around this pH. The results indicate that the Fe(OH) 3 solubility as well as the related intermolecular and surface forces play the predominant role in determining the Se 0 removal performance of the ferric coagulant. This work, for the first time, revealed the interaction mechanisms of Se 0 particle and amorphous Fe(OH) 3, providing useful insights on the performance of ferric coagulants on Se 0 particle removal from wastewater under various solution conditions. The experimental approach used in this work can be readily extended to other water treatment systems and processes such as polymer flocculation.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".