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6CCVD Research

Electrochemical decolorization of liquid digestate from coffee waste biomass using a boron-doped diamond anode

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-03-18
JournalInternational Journal of Environmental Science and Technology
AuthorsHaibin Chen, Gen Yoshida, Fetra J. Andriamanohiarisoamanana, Ikko Ihara
InstitutionsKobe University
AnalysisFull AI Review Included

Technical Documentation: Boron-Doped Diamond (BDD) for Advanced Electrochemical Oxidation (EO)

Section titled “Technical Documentation: Boron-Doped Diamond (BDD) for Advanced Electrochemical Oxidation (EO)”

Executive Summary

Section titled “Executive Summary”

This research validates the superior performance of Boron-Doped Diamond (BDD) anodes in the electrochemical decolorization of complex organic wastewater (spent coffee grounds digestate) for resource recycling.

  • Optimal Anode Performance: BDD anodes demonstrated significantly faster and more efficient decolorization compared to conventional Ti/Pt and Ti/IrO2 anodes.
  • High Removal Efficiency: The BDD process achieved 98.7% color removal (reaching the target Pt-Co value of 200) and 84.1% Chemical Oxygen Demand (COD) removal in 270 minutes.
  • Mechanism Advantage: The BDD’s high oxygen evolution overpotential promotes direct oxidation via physisorbed hydroxyl radicals (‱OH), minimizing competitive side reactions.
  • Nutrient Retention: Crucially for the target application (microalgae cultivation), the BDD process retained 87.4% of the essential nutrient Ammonium Nitrogen (NH4-N).
  • Fenton Enhancement: Increasing the initial Fe2+ concentration enhanced the Fenton reaction, leading to improved COD removal (up to 89.2% at 0.8 mM Fe2+).
  • Application: The resulting electrochemically oxidized liquid digestate is light-permeable and nutrient-rich, making it an ideal medium for sustainable microalgae cultivation.

Technical Specifications

Section titled “Technical Specifications”

The following hard data points were extracted from the research paper, highlighting the performance of the BDD anode configuration (BDD-BDD) at optimal conditions (1.5 A current, 35 °C).

ParameterValueUnitContext
Anode Material Performance OrderBDD > Ti/Pt > Ti/IrO2N/ADecolorization rate comparison
Color Removal (BDD)98.7%Achieved at 270 min
COD Removal (BDD)84.1%Achieved at 270 min
NH4-N Retention (BDD)87.4%Minimal degradation (12.6% decrease)
Time to Target Color (BDD)270minTo reach Pt-Co value of 200
Initial SCG Digestate Color11000 ± 850Pt-Co valueRaw liquid digestate
Final EO Digestate Color< 200Pt-Co valueElectrochemically oxidized liquid
Optimal Applied Current1.5AFastest absorbance decay
Operating Temperature35°CMaintained via water bath
Immersed Electrode Area35cm2Anode/Cathode area
Inter-Electrode Gap0.5cmReactor setup
Maximum COD Removal89.2%Achieved with 0.8 mM Fe2+ addition

Key Methodologies

Section titled “Key Methodologies”

The electrochemical oxidation process relied on rigorous pre-treatment and precise control of BDD electrode parameters.

  1. Digestate Pre-treatment: Raw Spent Coffee Grounds (SCG) digestate was filtered, centrifuged twice (4347×g), and subjected to membrane filtration (0.2 ”m pore size) to remove suspended solids (SS) and large macromolecules.
  2. Solution Preparation: The liquid digestate was diluted two-fold for the EO experiments.
  3. Electrode Configuration: The primary setup used a Boron-Doped Diamond (BDD) anode and a BDD cathode. Comparative tests utilized Ti/Pt and Ti/IrO2 anodes.
  4. Reactor Conditions: Experiments were performed in a 500 mL flask reactor (400 mL solution volume) with the temperature maintained at 35 °C using a water bath.
  5. Current Control: Constant current conditions were applied using a DC power supply, investigating a range from 0.6 A to 2.0 A.
  6. Fenton Enhancement: Ferrous ion (Fe2+) concentrations (0.1 mM to 0.8 mM) were introduced to evaluate the enhancement of the Fenton reaction for improved COD removal.
  7. Kinetic Analysis: Decolorization kinetics were modeled using a pseudo-first-order reaction (A = Aoe-kC) to determine the relationship between absorbance decay and electric charge.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

6CCVD is the expert supplier of MPCVD diamond materials required to replicate, scale, and advance this critical electrochemical research. Our capabilities directly address the material and customization needs demonstrated in this study.

Applicable Materials

Section titled “Applicable Materials”

The success of this research hinges entirely on the unique properties of the BDD anode.

  • Material Recommendation: Heavy Boron-Doped Polycrystalline Diamond (PCD) Wafers.
    • Justification: Our BDD material provides the high overpotential (2.2-2.6 V) necessary to generate physisorbed hydroxyl radicals (‱OH) efficiently, ensuring high COD removal and minimal parasitic NH4-N degradation, as demonstrated in the paper.
  • Cathode Recommendation: BDD Substrates.
    • Justification: The study utilized a BDD cathode. 6CCVD supplies robust BDD substrates up to 10mm thick, offering long-term stability and high performance for the cathodic oxygen reduction required in the EO process.

Customization Potential

Section titled “Customization Potential”

The experiment used specific electrode dimensions (35 cm2 immersed area) and compared various anode coatings. 6CCVD specializes in providing custom solutions tailored to specific reactor designs.

Research Requirement6CCVD Solution & CapabilityTechnical Advantage
Custom Electrode DimensionsPlates/Wafers up to 125mm (PCD)We provide custom laser cutting and shaping services to match the exact 35 cm2 immersed area or scale up to larger electrode sizes for pilot plant development.
High-Quality Surface FinishPolishing: Ra < 5nm (Inch-size PCD)Consistent surface roughness is vital for reproducible electrochemistry. Our polishing ensures uniform current density and predictable radical generation across the entire active area.
Comparative Anode TestingCustom Metalization (Ti, Pt, Ir, Au)The study compared BDD against Ti/Pt and Ti/IrO2. 6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for researchers requiring custom contacts or specific metal-oxide coatings on diamond substrates for comprehensive material comparison.
Thickness RequirementsSCD/PCD Thickness (0.1”m - 500”m)We can tailor the BDD film thickness to optimize conductivity and mechanical stability based on the required current density and operational lifetime of the electrochemical cell.

Engineering Support

Section titled “Engineering Support”

The successful application of BDD in advanced wastewater treatment requires precise material selection based on the target contaminants and desired nutrient retention.

  • Application Focus: 6CCVD’s in-house PhD team specializes in material selection for advanced electrochemical applications, including wastewater remediation, resource recycling, and electro-Fenton processes.
  • Consultation: We offer expert consultation on optimizing boron doping levels and substrate preparation to maximize hydroxyl radical generation and minimize competitive reactions (like oxygen evolution or hypochlorite formation) crucial for projects requiring high NH4-N retention.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Abstract Liquid digestate can be used to provide nutrients for microalgae cultivation but the medium needs to be clear and colorless. The aim of this work was to use liquid digestate from coffee waste biomass to produce a light-permeable medium for microalgae cultivation. A boron-doped diamond anode was applied for electrochemical decolorization of the digestate. The electrochemical oxidation process reduced the platinum-cobalt color value by up to 97% and the chemical oxygen demand by 84.1%. After electrochemical oxidation, 87.4% of the ammonium nitrogen (NH 4 -N) was retained. Decolorization of the spent coffee grounds liquid digestate was compared with that of dairy cow manure liquid digestate. It took 90 min longer to fully decolorize the spent coffee grounds liquid digestate compared with the dairy cow manure liquid digestate. The boron-doped diamond anode performed better in the decolorization than Ti/IrO 2 and Ti/Pt anodes. The effects of the initial Fe 2+ concentration and current on the electrochemical oxidation process were also evaluated. Increasing the initial Fe 2+ concentration enhanced the Fenton reaction and chemical oxygen demand removal. A higher current enhanced the electrochemical decolorization process and side reactions. Electrochemical oxidation using a boron-doped diamond anode is a promising method for producing an appropriate medium for microalgae cultivation because it promotes decolorization of liquid digestate and retains most of the NH 4 -N.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1999 - Handbook of chlorination and alternative disinfectants

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