Electrocoagulation with Polarity Reversal for Treatment of Produced Water
Bibliographic record
Abstract
Electrocoagulation (EC) is a cost-effective and reliable technology to treat water and wastewater and has the ability to remove many types of contaminants. Studies have shown that EC operated with aluminum or iron electrodes exhibits higher treatment efficiencies than traditional chemical coagulation with aluminum sulfate or ferric chloride salts [1], [2]. EC involves the in-situ generation of metal hydroxide coagulant by the electrochemical dissolution of sacrificial metal anodes using a direct current, combined with generation of hydroxide ions at the cathode. However, material precipitation on the electrodes associated with long term operation is a major problem hindering the scale up of EC [3]. The growth of electrode surface layers increases passivation, which reduces the treatment efficiency and increases operating costs [4]. Polarity reversal during electrocoagulation, i.e. intermittently changing the direction of the current, is a method that can remove passivation layers on the electrodes formed during direct current operation [5]. The main goal of this study was to investigate the effect of polarity reversal on the reaction and electrode fouling mechanisms as well as the performance of electrocoagulation for the treatment of SAGD produced water. Total organic carbon and silicon removal efficiencies were measured to evaluate treatment performance. Laser scanning confocal microscopy was used to monitor the pH distribution close to electrodes as well as the formation of solid products in an electrocoagulation cell. Customized polycarbonate bench scale reactors were used to study the relationship between coagulant production, polarity reversal frequency, solution composition, and flowrate. The cycle time of the polarity reversals was varied from 5 to 600 s, and the Reynolds numbers was varied between 30 to 200. The Faradaic efficiencies for the coagulant dissolution at different operating conditions were determined by digesting the solid products followed by elemental analysis. The evolution of pH during polarity reversal revealed that at higher frequencies or higher flow rates, the thickness of the interfacial pH boundary layer was lower. The quantification of pH was used to study the effect of pH on passivation layer stability. It was found that at higher frequencies, Faradaic efficiencies were lower for EC with iron electrodes, whereas increased efficiencies were observed for aluminum electrodes due to increased susceptibility to non-Faradaic corrosion. EC using aluminum electrodes (Al-EC), employing polarity reversal at all frequencies led to a reduction in cell voltage and therefore a reduction in the required energy for treatment. References [1] M. Eyvaz, M. Kirlaroglu, T. S. Aktas, and E. Yuksel, “The effects of alternating current electrocoagulation on dye removal from aqueous solutions,” Chem. Eng. J. , vol. 153, no. 1–3, pp. 16–22, 2009. [2] P. K. Holt, G. W. Barton, M. Wark, and C. A. Mitchell, “A quantitative comparison between chemical dosing and electrocoagulation,” Colloids Surfaces A Physicochem. Eng. Asp. , vol. 211, no. 2–3, pp. 233–248, 2002. [3] S. Garcia-Segura, M. M. S. G. Eiband, J. V. de Melo, and C. A. Martínez-Huitle, “Electrocoagulation and advanced electrocoagulation processes: A general review about the fundamentals, emerging applications and its association with other technologies,” Journal of Electroanalytical Chemistry , vol. 801. pp. 267–299, 2017. [4] C. M. van Genuchten, S. R. S. Bandaru, E. Surorova, S. E. Amrose, A. J. Gadgil, and J. Peña, “Formation of macroscopic surface layers on Fe(0) electrocoagulation electrodes during an extended field trial of arsenic treatment,” Chemosphere , vol. 153, pp. 270–279, 2016. [5] M. Eyvaz, “Treatment of brewery wastewater with electrocoagulation: Improving the process performance by using alternating pulse current,” Int. J. Electrochem. Sci. , vol. 11, no. 6, pp. 4988–5008, 2016.
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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".