Epichlorohydrin-crosslinked chitosan hydrogels as recyclable adsorbents for phosphate removal from aqueous solutions and municipal wastewater
Bibliographic record
Abstract
Phosphorus is an essential nutrient; however, when present in the environment, it can trigger eutrophication. Therefore, its removal from aquatic systems is key to ensure high water quality. Adsorption has shown to be an efficient, simple and versatile water treatment for the removal of a variety of contaminants. Chitosan (CS) is a bio-polymeric material, widely used as adsorbent, capable of self-assembly to form hydrogels. Yet, the material is unstable at pH < 3. The stability can be improved with a crosslinking agent, such as epichlorohydrin (ECH), which also improves the adsorption capacity of the chitosan-based adsorbents. Chemically crosslinked chitosan (CS-ECH) hydrogels are positively charged, having the potential to be used as adsorbents for phosphorus (as orthophosphate) and other anionic contaminants. For this research, CS-ECH hydrogels with chitosan:crosslinker ratios of 1:0, 1:0.5, 1:0.8, 1:1 and 1:1.2 were prepared and evaluated for the removal of phosphorus. The best removal performance corresponded to CS-ECH at 1:0.5 chitosan:crosslinker ratio, at an optimal pH of 3, reaching an adsorption capacity of around 101 mg PO 4 /g of hydrogel. Adsorption kinetics were fitted to a pseudo-first order kinetic model and the Langmuir isotherm. Recyclability tests on phosphate-saturated hydrogels (10 mg PO₄/g and 100 mg PO₄/g) using NaOH treatments revealed a maximum desorption efficiency at pH 11. After three adsorption-desorption cycles, the material retained at least 77 % of its initial removal capacity. Additionally, CS-ECH removed approximately 78 % of phosphate from filtered municipal wastewater, demonstrating its potential for environmental applications. • Epichlorohydrin-crosslinked chitosan hydrogels are efficient phosphate adsorbents. • Adsorption was described by pseudo-second order kinetic model and Langmuir isotherm. • The adsorbents were recycled 3 times, with at least 77 % of its adsorption capacity. • Phosphate adsorption was evaluated on municipal wastewater.
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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) | 0.001 | 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 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".