Electrochemical Ferrates for Drinking Water Treatment: Quantification, Synthesis and Degradation Studies
Notice bibliographique
Résumé
Ferrate ions are highly oxidizing and unstable species which are challenging to quantify and analyze. They are, however, becoming increasingly recognized as an excellent candidate for a number of applications such as water treatment. Development of ferrate-based technologies for drinking water treatment in remote area requires: a) an accurate assay of the produced ferrates, b) better understanding of the stability properties and c) in-situ electrochemical generation at neutral pH conditions. In order to investigate the possibility of using on-site generated ferrates for treatment of drinking water, we conducted a thorough research program covering the following topics: 1) Quantification of Electrochemically generated Ferrates. Four analytical methods (existing and new) for quantification of ferrates were investigated and compared. These methods include titrimetric analysis, and spectrometric techniques such as direct colorimetric, measurements of ABTS or NaI colorimetric. In terms of accuracy, cost, simplicity and time required the modified indirect UV-Vis/NaI method is shown to be the most effective of all the four methods investigated. 2) Electrochemical ferrate stability. Stability of ferrate species, produced electrochemically for on-site treatment of drinking water, was studied for a number of conditions including: pH, temperature, initial concentration effects, and presence of impurities in order to assess the degradation process quantitatively. Degradation of ferrates for the pH range of 5 to 13 appears to have a first order kinetics behavior. Degradation of ferrates over a temperature range of 5 ºC to 60 °C shows an Arrhenius-type behavior with an activation energy of 348 kJ mol -1 . Initial rate analysis of degradation reveals a reaction order of about 1. Impact of potential impurities, such as salts and natural organic matter (NOM), source of water (e.g., tap, deionized and water from natural lake) were also studied and results will be presnted. 3) Electrochemical generation of ferrate species at neutral conditions. Undivided batch (100 mL) cell. An undivided batch cell was used to study the electrochemical generation of ferrate species at neutral conditions (pH ~ 7) using boron-doped diamond (BDD) electrodes and iron (III) salts for applications in drinking water treatment. The impact of several relevant variables, including current density (5-55 mA cm -2 ), pH (5-9), type and concentration of the dissolved iron salts on the production of ferrates were examined. In addition, linear sweep voltammetry (LSV) studies were conducted using buffer electrolytes with and without the presence of iron (III) to decouple the parasitic oxygen evolution reaction. The LSV measurements in the presence of iron (III) and with a neutral electrolyte exhibit oxidation peaks centered ~ 2.0 V ( vs. SHE), indicating the production of ferrates at this pH. The rate of ferrate generation is not strongly affected by the pH condition; however, current density and the source of iron were found to have a higher impact on the production rate of ferrates. The efficacy of the process was higher using FeCl 3 compared to other salts such as Fe 2 O 4 and FeO(OH). Semi-batch (2 L) reactor. This approach provided a number of improvements over the batch cell, including: recirculation, proper temperature control, lower cell resistance, excellent mixing, provision for the use of ion exchange membrane, and in-situ pH control. The preliminary results from this benchtop semi-batch reactor showed an improvement in the current effiency from 8% (batch cell) to 75% (semi-batch cell). Overall, about 8 mmol of ferrates was generated during a 2 hour electrosynthesis period exceeding the water treatment targets of about 14 µmol of ferrates. Figure 1
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 | 0,001 | 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) | 0,000 | 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 tête enseignante, 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 ».