Simultaneous Manganese Removal and Remineralization of Soft Waters Via Calcite Contactor
Notice bibliographique
Résumé
phase, the negative impact of newly-formed Mn-layer on calcite dissolution rate using continuous desorption-dissolution experiments in smaller columns was investigated.For an elevated Mn concentration (i.e.5.0 mg Mn L -1 ) in the feed water, the coated layer was mainly composed of Mn which inhibits the mass transfer from the calcite core to the liquid phase.The superficial layer was identified as 5.2% Mn oxides (MnOx) by X-ray photoelectron spectroscopy (XPS).Therefore, it is postulated that Mn removal starts with an ion exchange sorption reaction between soluble Mn 2+ from aqueous phase and Ca 2+ from the CaCO3 matrix which is followed by a slow recrystallization of MnCO3 into MnO2.On the other hand, when the Mn content in the feed water was lower (i.e.0.5 mg Mn L -1 ), a considerably lower amount of MnOx was detected on the coated media.For all the examined conditions, the formation of this coating improved Mn removal due to the autocatalytic nature of adsorption/oxidation of dissolved manganese by MnOx.As for the third phase, the long-term efficiency of a calcite contactor was modeled using a mechanistic model based on calcite dissolution and progressive formation of a MnO2 layer which was implemented in PHREEQC software using a MATLAB interface via IPHREEQC modules to predict the reduction in hardness release expected in long-term operation.The model was calibrated with experimental data and resulted in realistic breakthrough curves.In order to accurately predict the pH of the effluent stream, a slow-rate recrystallization of MnCO3 into MnO2 was implemented (compared to fast precipitation of MnO2 or absence of MnO2 formation).Finally, given that after long-term operation of the calcite contactor in elevated Mn concentrations, the remineralization objective was not fully met, a possible solution was tested using a blend of calcite and Corosex TM (MgO) as the filtration media.For this purpose, first optimum ratio of 80% / 20% for Calcite/ Corosex TM was obtained, then the column was operated under elevated Mn concentration (5 mg L -1 Mn 2+ ) with the chosen ratio to investigate the efficiency of the contactor in remineralization of soft water with simultaneous Mn removal.The column demonstrated high efficiency: in the long-term operation, the contactor was able to remove over 99% of dissolved Mn from the synthetic feed water (SFW) and added above 40 mg CaCO3/L of hardness to the soft feed.The stable condition was reached much sooner than the previous phase when only calcite was used (10 h of operation versus above 100 h of operation).Accumulation of newly formed Mn residue increased the head loss overtime and caused filter clogging.It is important to note that using a blend of calcite and Corosex TM does not seem like a promising option for long-term operation if the Mn concentration in the feed is unrealistically high (i.e. 5 mg L -1 Mn 2+ ).However, for more realistic Mn concentrations (i.e.0.2 mg/L and less), adding a small portion of MgO to the filter would help to improve the hardness addition.
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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 ».