Electrosynthesis of Near-Neutral Ferrate Species for Drinking Water Treatment Using a Recirculating Batch Reactor
Bibliographic record
Abstract
High oxidation state iron species of ferrates (e.g., Fe (VI), Fe (V) and Fe (IV)) are very promising oxidants and are in particular excellent candidates for water treatment applications. Their advantages include, for instance, a higher redox potential (+2.2 V vs. SHE) than the commonly used ozone oxidant (+2.07 V vs. SHE), no production of carcinogenic and harmful disinfection by-products (DBPs – produced with disinfectants such as chlorine) and decomposition into benign ferric hydroxides which form excellent coagulants. Ferrates are known to remove many different types of pollutants, including organic matter such as biofilms, algae, and coliforms, and inorganic matter such as cyanide, heavy metals, and radionuclides, and bio-contaminants like viruses and chlorine-resistant bacteria. One approach in production of ferrates is oxidation of Fe 3+ -containing solutions using an inert anode electrode. The oxidation reaction can be expressed by: Fe 3+ + 4H 2 O → FeO 4 2- + 8H + + 3e - E 0 = -2.2 V vs. SHE On-site production of ferrates for drinking water treatment by electrochemical means avoids a number of challenges with respect to transport and storage of chemical ferrates and also allows for direct integration of the electrochemical process with the treatment chain. In earlier papers on electrochemical ferrates, we have reported on a novel analytical method of ferrate quantification, degradation of ferrate and production of ferrates in small batch-type reactors [1-3]. Here we present a semi-batch (2 L) reactor which includes recirculation, temperature control, lower cell resistance, excellent mixing, provision for the use of ion exchange membrane, and in-situ pH control. The reactor uses boron doped diamond (BDD), Fe (III) solution and can be operated with or without an ion exchange membrane. The impact of several variables including current density (5 - 15 mA cm -2 ), pH (5 - 9), concentration of the dissolved iron salts on the production of ferrates temperature (15 - 30 o C) and operation with/without membrane have been studied and will be presented. Current efficiencies of as high as 90% were reached for the first 20 minutes of operation using a 30 mM of Fe (III) feed and a current density of 45 mA cm -2 . The recirculating reactor results were successfully interpreted by a simple model which considered first order kinetics for Fe (VI) generation. References [1] M. Cataldo Hernandez, A. May, A. Bonakdarpour, M. Mohseni, D.P. Wilkinson, Can J. Chem , 95 (1) 2016. [2] M. Cataldo Hernandez, M. Stewart, A. Bonakdarpour, M. Mohseni, D.P. Wilkinson, Accepted for publication in the Canadian Journal of Chemical Engineering . [3] M. Cataldo Hernandez, R. Govindarajan, A. Bonakdarpour, M. Mohseni, D.P. Wilkinson, Accepted for publication in the Canadian Journal of Chemical Engineering . Figure 1
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".