研究目的
To enhance electrocatalytic H2O2 production using Co-based air-diffusion cathodes and apply it in photoelectro-Fenton processes for treating the organic pollutant bronopol in wastewater.
研究成果
The Co-based air-diffusion cathodes significantly enhanced H2O2 production, with up to 100% current efficiency at low current densities, and demonstrated good stability with minimal Co leaching. These cathodes improved the performance of EAOPs for bronopol treatment, with SPEF using a BDD anode and catalyzed cathode achieving the best results (94% mineralization). The process primarily produced formic acid as a by-product and converted bromine and nitrogen atoms to inorganic ions, though some refractory organic compounds remained. This work supports the potential for scaling up such electrochemical treatments for wastewater containing persistent organic pollutants.
研究不足
The study was conducted in a laboratory-scale pre-pilot plant, which may not fully represent industrial-scale conditions. The stability of the catalyzed cathodes was tested over multiple runs but long-term durability under varying real wastewater compositions was not extensively explored. The use of specific anodes (RuO2 and BDD) and controlled conditions (e.g., constant pH, temperature) may limit applicability to more complex environments. Additionally, the formation of unidentified organic by-products indicates incomplete mineralization, which could be a constraint for certain applications.
1：Experimental Design and Method Selection:
The study involved synthesizing (Co, S, P)-decorated MWCNTs via a hydrothermal route to manufacture air-diffusion cathodes. These were tested in a pre-pilot plant for H2O2 electrogeneration and treatment of bronopol solutions using various electrochemical advanced oxidation processes (EAOPs) like EO-H2O2, EF, PEF, and SPEF, with comparisons to uncatalyzed cathodes and different anodes (RuO2-based and BDD).
2：Sample Selection and Data Sources:
Aqueous solutions of bronopol (0.28-0.84 mM) in 0.050 M Na2SO4 at pH 3.0 were used, with Fe2+ catalyst added for Fenton-based processes. Samples were collected over time for analysis.
3：28-84 mM) in 050 M Na2SO4 at pH 0 were used, with Fe2+ catalyst added for Fenton-based processes. Samples were collected over time for analysis. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a filter-press flow cell, air-diffusion cathodes (catalyzed and uncatalyzed), anodes (RuO2-based and BDD), DC power supply (Agilent Technologies N5746A), UVA lamp (Omnilux 27E 160-W), spectrophotometer (Shimadzu 1800 UV/Vis), TOC analyzer (Shimadzu VCSN), HPLC (Waters 600), ion chromatography system, ICP-OES (Perkin Elmer Optima 3200 L), and radiometer (Kipp & Zonen CUV 5). Materials included MWCNTs, chemicals for catalyst synthesis (e.g., CoCl2·6H2O, Na2S2O3·5H2O, S, NaH2PO2·H2O), Nafion? dispersion, carbon cloth substrate, bronopol, Na2SO4, FeSO4·7H2O, and various reagents for analytical methods.
4：5). Materials included MWCNTs, chemicals for catalyst synthesis (e.g., CoCl2·6H2O, Na2S2O3·5H2O, S, NaH2PO2·H2O), Nafion? dispersion, carbon cloth substrate, bronopol, Na2SO4, FeSO4·7H2O, and various reagents for analytical methods. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Cathodes were manufactured by spraying catalyst ink onto carbon cloth. Electrolyses were conducted at constant current densities (10-40 mA cm-2) in a 2.5-L pre-pilot plant with continuous air supply. Solutions were treated for up to 360 min, with samples taken periodically for H2O2, bronopol concentration, TOC, carboxylic acids, and inorganic ions analysis. Processes included EO-H2O2 (no light), EF (with Fe2+), PEF (with UVA light), and SPEF (with sunlight).
5：5-L pre-pilot plant with continuous air supply. Solutions were treated for up to 360 min, with samples taken periodically for H2O2, bronopol concentration, TOC, carboxylic acids, and inorganic ions analysis. Processes included EO-H2O2 (no light), EF (with Fe2+), PEF (with UVA light), and SPEF (with sunlight). Data Analysis Methods:
5. Data Analysis Methods: H2O2 concentration was determined spectrophotometrically using the metavanadate method. Bronopol decay was monitored by HPLC, TOC by a TOC analyzer, carboxylic acids by ion-exclusion HPLC, and inorganic ions by ion chromatography and ICP-OES. Kinetic analyses assumed pseudo-first-order decay, and efficiencies (current efficiency for H2O2, mineralization current efficiency) and energy consumption were calculated based on standard formulas.
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Nafion? perfluorinated resin solution
5 wt.%
Sigma-Aldrich
Used as a binder in the catalyst ink for manufacturing air-diffusion cathodes to ensure good adhesion and conductivity.
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DC power supply
N5746A
Agilent Technologies
Provided constant current density for electrolysis experiments and displayed cell voltage.
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UV/Vis spectrophotometer
1800
Shimadzu
Used to determine H2O2 concentration via the metavanadate method at λ = 450 nm.
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TOC analyzer
VCSN
Shimadzu
Measured total organic carbon content in solutions to assess mineralization.
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ICP-OES spectrometer
Optima 3200 L
Perkin Elmer
Determined leached cobalt concentrations from catalyzed cathodes.
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MWCNTs
OD < 8 nm, L 10-30 μm, COOH content 3.86 wt.%
Cheap Tubes Inc.
Used as a base material for synthesizing electrocatalysts and manufacturing air-diffusion cathodes to enhance H2O2 production.
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UVA lamp
Omnilux 27E 160-W
Omnilux
Used for UVA irradiation in PEF experiments to photolyze Fe(III) complexes and regenerate Fe2+ catalyst.
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HPLC system
600
Waters
Used for reversed-phase and ion-exclusion chromatography to monitor bronopol concentration and quantify carboxylic acids.
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Radiometer
CUV 5
Kipp & Zonen
Measured UV irradiance during SPEF experiments.
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Carbon cloth substrate
A7NCV2.1 ELAT? V2.1
BASF
Used as the substrate for manufacturing air-diffusion cathodes, providing a large surface area and diffusion layer.
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