Flocculation kinetics of precipitated calcium carbonate induced by functional nanocellulose
Notice bibliographique
Résumé
ABSTRACTThe interactions between precipitated calcium carbonate (PCC) and electrosterically stabilized nanocrystalline cellulose (ENCC) and dissolved carboxylated cellulose (DCC) have been studied in this thesis. ENCC and DCC usually have a high carboxylate content (3.5 mmol/g or higher) and can be produced by periodate, chlorite and TEMPO oxidations. ENCC/DCC showed a high flocculation efficiency with PCC particles and induced PCC flocculation by a combination of electrostatic and bridging forces. ENCC/DCC induces the maximum PCC flocculation when PCC particles reach to isoelectric point. Novel nanocellulose particles were prepared by periodate oxidation in this study. For partial oxidation (degree of substitution (DS)<2), three products were generated: fibrous cellulose, rod-like dialdehyde cellulose (DAC) nanofibers, which we refer to as sterically stabilized nanocrystalline cellulose (SNCC), and dissolved DAC which we refer to as dialdehyde modified cellulose (DAMC). SNCC has similar dimension (100–200 nm in length and 5–8 nm in width) as conventional nanocrystalline cellulose (NCC) made by sulfuric acid hydrolysis. SNCC was characterized and its properties were compared to NCC. In addition, morphological features and size distributions of three SNCCs prepared by different degrees of oxidation were measured by transmission electron microscopy and dynamic light scattering (DLS). It shows that the three SNCCs have similar diameters (5-10 nm). However, the average length of SNCC decreases with aldehyde content: from approximately 590 nm after 26 hrs of oxidation to 100 nm for an oxidation period of 84 hrs. It indicates that the morphology of SNCC can be well controlled by the degree of periodate oxidation, which depends on the amount of periodate and the reaction time. Based on this observation, we propose that periodate reacts preferentially with the amorphous region of cellulose, followed by proceeding at the boundary of amorphous and crystalline regions. The steric stability of SNCC is proved by DLS when adding cosolvents into aqueous SNCC suspensions. The flocculation of PCC induced by SNCC was also studied. SNCC particles can bridge PCC to induce flocculation at low dosage (above 1mg/g). SNCC induced the maximum flocculation when its fractional coverage was more than half coverage because SNCC particles become unstable after deposition on PCC. Adsorption isotherms of three SNCCs and dialdehyde modified cellulose (DAMC) on PCC particles were measured. It was found that DAMC had a higher affinity than three SNCCs with different aldehyde contents, and the affinity of SNCC increased with reaction time. This indicates DAMC chains adsorb stronger than nanocrystalline parts of SNCC on PCC.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».