| Metadata | Details |
|---|
| Publication Date | 2020-06-28 |
| Journal | Processes |
| Authors | Mauricio Chiliquinga, Patricio J. Espinoza-Montero, Oscar M. Rodriguez, Alain R. Picos-BenĂtez, Erick R. Bandala |
| Institutions | Universidad de Guanajuato, National Polytechnic School |
| Citations | 12 |
| Analysis | Full AI Review Included |
- Core Technology: The study successfully demonstrated the viability of a synergistic Advanced Oxidation Process (AOP) combining electro-oxidation (EOx) via hydroxyl radicals (OH) and the in situ electrochemical generation of Ferrate(VI) ions ([Fe(VI)]) using a Boron-Doped Diamond (BDD) anode.
- Performance Benchmark: The combined EOx/[Fe(VI)] process significantly outperformed EOx alone, achieving up to 98% Blue BR (BBR) dye discoloration in 60 minutes, compared to a maximum of 78% for EOx alone (under best conditions).
- Mineralization Improvement: Chemical Oxygen Demand (COD) reduction was boosted from 37% (EOx alone) to 61% when 12 mM FeSO4 was added to generate [Fe(VI)].
- Optimal Conditions: The highest degradation rates were achieved using 0.05 M Na2SO4 as the electrolyte, a current density of 30 mA cm-2, and 12 mM FeSO4 precursor.
- Electrolyte Effect: Cyclic Voltammetry (CV) confirmed that the Na2SO4 medium favored ferrate generation at a lower potential (0.78 V vs. Ag/AgCl) compared to HClO4 (0.90 V), leading to faster degradation kinetics.
- Byproduct Control: The simultaneous action of OH and [Fe(VI)] rapidly oxidized reaction intermediates, resulting in minimal accumulation of recalcitrant carboxylic acids (oxalic acid concentration was reduced from almost 20 mg/L in EOx alone to 2 mg/L in the combined process).
| Parameter | Value | Unit | Context |
|---|
| Anode Material | Boron-Doped Diamond (BDD) | N/A | Working electrode |
| Anode Surface Area (EOx) | 2.5 | cm2 | Discoloration assays |
| Optimal Current Density (j) | 30 | mA cm-2 | Highest degradation rate |
| Initial BBR Dye Concentration | 50 | mg/L | All trials |
| Optimal Electrolyte | 0.05 M Na2SO4 | M | pH 3 |
| Optimal FeSO4 Concentration | 12 | mM | Ferrate precursor |
| Optimal Discoloration Efficiency | 98 | % | Achieved in 60 min |
| Optimal COD Reduction | 61 | % | Achieved in 90 min |
| EOx Alone COD Reduction | 37 | % | Baseline comparison |
| Ferrate Generation Potential (Na2SO4) | 0.78 | V vs. Ag/AgCl | Lower potential favored degradation |
| Ferrate Generation Potential (HClO4) | 0.90 | V vs. Ag/AgCl | Higher potential required |
| Highest Pseudo-First Order Rate (k1) | 0.0703 | min-1 | Optimal conditions (Na2SO4, 30 mA cm-2, 12 mM FeSO4) |
| BBR Dye Molecular Weight | 678.68 | g/mol | Chemical formula C32H28N2Na2O8S2 |
| Reactor Volume | 100 | mL | Laboratory tank reactor |
- Electrochemical Characterization: Cyclic Voltammetry (CV) was used in a three-electrode cell (BDD working, Pt counter, Ag/AgCl reference) to confirm the overoxidation of Fe(II) to Fe(VI). CV analysis determined the optimal electrolyte (0.05 M Na2SO4) based on the lower potential required for ferrate generation (0.78 V vs. Ag/AgCl).
- Reactor Operation: Discoloration assays were conducted in galvanostatic mode in a 100 mL stirred tank reactor (200 rpm) using a BDD anode (2.5 cm2) and a Pt cathode.
- Oxidant Generation: The BDD anode simultaneously generated hydroxyl radicals (OH) via water oxidation and ferrate ions ([Fe(VI)]) via the oxidation of added ferrous sulfate (FeSO4) precursor.
- Kinetic Testing: Experiments systematically varied current density (7, 15, 30 mA cm-2) and FeSO4 concentration (1, 6, 12 mM) in both HClO4 and Na2SO4 media (pH 3).
- Performance Metrics: Discoloration kinetics were monitored by UV-Vis spectrophotometry (Îť = 695 nm). Mineralization was quantified by Chemical Oxygen Demand (COD) reduction (Standard Methods 5220D).
- Byproduct Analysis: Liquid Chromatography (HPLC) with ion-exclusion was employed to identify and quantify the evolution of carboxylic acid intermediates (oxalic acid) during the degradation process.
- Textile and Tanning Wastewater Treatment: Direct application for the removal of highly recalcitrant azo dyes (like Blue BR) and associated high COD loads found in industrial effluents.
- Advanced Water Purification (AOPs): Implementation of BDD-based electrochemical reactors for generating powerful, short-lived oxidants (OH) and stable, high-valence oxidants ([Fe(VI)]) in a single step, enhancing pollutant destruction efficiency.
- Water Disinfection and Coagulation: Ferrate(VI) is a known bifunctional agent. This technology offers a method for in situ generation of ferrate, suitable for simultaneous disinfection and subsequent coagulation (via Fe(III) reduction byproduct) in municipal or industrial water streams.
- Minimization of Toxic Byproducts: The synergistic process ensures rapid oxidation of intermediates (like oxalic acid), addressing a major challenge in conventional AOPs where partially oxidized, toxic compounds may accumulate.
- Electrochemical Reactor Design: Provides critical data for optimizing BDD electrode operation, specifically defining optimal current densities and electrolyte compositions (Na2SO4) for efficient ferrate production in environmental applications.
View Original Abstract
In this study, electro-oxidation (EOx) and in situ generation of ferrate ions [Fe(VI)] were tested to treat water contaminated with Blue BR dye (BBR) using a boron-doped diamond (BDD) anode. Two electrolytic media (0.1 M HClO4 and 0.05 M Na2SO4) were evaluated for the BDD, which simultaneously produced oxygen radicals (â˘OH) and [Fe(VI)]. The generation of [Fe(VI)] was characterized by cyclic voltammetry (CV) and the effect of different current intensity values (e.g., 7 mA cmâ2, 15 mA cmâ2, and 30 mA cmâ2) was assessed during BBR degradation tests. The discoloration of BBR was followed by UV-Vis spectrophotometry. When the EOx process was used alone, only 78% BBR discoloration was achieved. The best electrochemical discoloration conditions were found using 0.05 M Na2SO4 and 30 mA cmâ2. Using these conditions, overall BBR discoloration values up to 98%, 95%, and 87% with 12 mM, 6 mM, and 1 mM of FeSO4, respectively, were achieved. In the case of chemical oxygen demand (COD) reduction, the EOx process showed only a 37% COD reduction, whereas combining [Fe(VI)] generation using 12 mM of FeSO4 achieved an up to 61% COD reduction after 90 min. The evolution of reaction byproducts (oxalic acid) was performed using liquid chromatography analysis.
- 2018 - Comparative study for degradation of industrial dyes by electrochemical advanced oxidation processes with BDD anode in a laboratory stirred tank reactor [Crossref]
- 2009 - On-line production of ferrate with an electrochemical method and its potential application for wastewater treatmentâA review [Crossref]
- 2004 - Effect of sp2-Bonded Nondiamond Carbon Impurity on the Response of Boron-Doped Polycrystalline Diamond Thin-Film Electrodes [Crossref]
- 2018 - Electrosynthesis of ferrate in a batch reactor at neutral conditions for drinking water applications [Crossref]
- 2018 - Degradation of ferrate species produced electrochemically for use in drinking water treatment applications [Crossref]
- 2019 - Contaminants of emerging concern removal from real wastewater by UV/free chlorine process: A comparison with solar/free chlorine and UV/H2O2 at pilot scale [Crossref]
- 2006 - Study on Fe (VI) species as a disinfectant: Quantitative evaluation and modeling for inactivating Escherichia coli [Crossref]
- 2018 - Abatement of the antibiotic levofloxacin in a solar photoelectro-Fenton flow plant: Modeling the dissolved organic carbon concentration-time relationship [Crossref]
- 2019 - Electrochemical oxidation of dibenzothiophene compounds on BDD electrode in acetonitrile-water medium [Crossref]