Treatment of hydrothermal carbonization process water by electrochemical oxidation - Assessment of process performance

At a Glance

Metadata	Details
Publication Date	2022-11-13
Journal	Environmental Research
Authors	Judith González-Arias, M.A. de la Rubia, M.E. Sánchez, Xiomar Gómez, Jorge Cara-Jiménez
Institutions	Universidad Autónoma de Madrid, Universidad de León
Citations	21
Analysis	Full AI Review Included

Technical Documentation & Analysis: Electrochemical Oxidation using BDD Anodes

Reference: J. González-Arias et al. (2023). Treatment of hydrothermal carbonization process water by electrochemical oxidation: Assessment of process performance. Environmental Research 216.4: 114773.

Executive Summary

This documentation analyzes the application of Boron-Doped Diamond (BDD) anodes in the electrochemical oxidation (EO) of highly contaminated process water (PW) from hydrothermal carbonization (HTC) of olive tree pruning.

Validated BDD Efficacy: Boron-Doped Diamond (BDD) electrodes were confirmed as highly effective anodes for the mineralization of recalcitrant organic pollutants in complex wastewater streams.
Superior Removal Rates: EO experiments using supporting electrolytes (Na₂SO₄ or NaCl) achieved significantly higher Total Organic Carbon (TOC) removal (30-40%) compared to the control experiment (17% TOC removal).
Hydroxyl Radical Mechanism: The BDD anode’s capability to generate highly reactive, non-adsorbed hydroxyl radicals (·OH) is the primary mechanism driving the high mineralization efficiency of volatile fatty acids (VFAs) and complex aromatic compounds.
Key Operational Parameters: Optimal organic matter removal is strongly dependent on reaction time (up to 300 min) and high solution conductivity, achieved by adding promoters like NaCl.
Scale-Up Challenge: The study identified high Specific Energy Consumption (SEC), ranging from 1 to 45 €/kg CODremoved, emphasizing the critical need for optimized BDD electrode geometry and advanced cell design for industrial feasibility.
6CCVD Value Proposition: 6CCVD specializes in manufacturing high-performance MPCVD BDD plates and custom electrodes necessary to optimize cell design, reduce SEC, and scale this technology for commercial wastewater treatment applications.

Technical Specifications

The following hard data points were extracted from the experimental setup and performance results:

Parameter	Value	Unit	Context
Anode Material	Boron Doped Diamond (BDD)	N/A	Used in a commercial flow cell
Effective Anode Area	42	cm²	BDD electrode surface area
Electrode Gap	5	mm	Distance between BDD anode and cathode
Applied Voltage	25	V	Constant potential applied across the cell
Operating Temperature	25 ± 1	°C	Batch mode, room temperature
Current Density Range	1.38 to 11.79	mA/cm²	Dependent on electrolyte and time
Max TOC Removal	40	%	Achieved with NaCl supporting electrolyte (C_300 min)
Max COD Removal	40	%	Achieved with NaCl supporting electrolyte (C_300 min)
Max Specific Energy Consumption (SEC)	156.89	kWh/kg CODremoved	Highest consumption (B_300 min)
Treatment Cost Range	1 to 45	€/kg CODremoved	Dependent on EO time and electrolyte used
Supporting Electrolyte Conductivity (NaCl)	15.80	mS/cm²	Condition C, leading to highest removal

Key Methodologies

The electrochemical oxidation (EO) experiments were conducted using the following parameters and procedures:

Feedstock Source: Process water (PW) obtained from the hydrothermal carbonization (HTC) of olive tree pruning biomass.
Electrochemical Cell: A 75 mL batch cell supplied by Pro-Aqua Diamond Electrode Production Ltd, GmbH, featuring a bi-polar BDD anode and cathode.
Electrode Geometry: Fixed effective area of 42 cm² and a fixed inter-electrode distance of 5 mm.
Electrolyte Conditions: Three test conditions were established to assess the effect of conductivity adjustment:
- A (Control): Raw PW (EC: 1.44 mS/cm²).
- B (Na₂SO₄): Conductivity adjusted to 10 ± 0.5 mS/cm² (~10 g/L Na₂SO₄).
- C (NaCl): Conductivity adjusted to 5.0 ± 0.5 mS/cm² (~10 g/L NaCl).
Operating Parameters: Constant applied voltage of 25 V at room temperature (25 ± 1 °C).
Reaction Time: Four reaction times were tested for each condition: 30, 60, 150, and 300 minutes.
Analytical Techniques: Total Organic Carbon (TOC), Chemical Oxygen Demand (COD), and identification of chemical species (including volatile fatty acids, VFAs) via Gas Chromatography Mass Spectrometry (GC-MS).

6CCVD Solutions & Capabilities

This research confirms the critical role of high-quality Boron-Doped Diamond (BDD) anodes in advanced oxidation processes for industrial wastewater treatment. 6CCVD is uniquely positioned to supply the materials and engineering expertise required to replicate this research and scale the technology for commercial deployment.

Applicable Materials

To replicate or extend this research, high-performance BDD electrodes are essential. 6CCVD recommends the following materials from our catalog:

Heavy Boron Doped Diamond (BDD) Plates: Our MPCVD BDD material offers exceptional chemical stability, strong corrosion resistance, and a wide potential window, making it ideal for high-load, complex wastewater streams like HTC process water. We provide BDD with optimized doping levels to maximize hydroxyl radical generation (·OH) efficiency, directly addressing the core mechanism of this EO process.
Polycrystalline Diamond (PCD) Substrates: For large-area industrial applications, 6CCVD can supply PCD substrates up to 125mm in diameter, which can be coated with BDD films to create large, cost-effective electrodes suitable for flow-cell reactors.

Customization Potential

The study highlights that high energy consumption (SEC) is the main barrier to commercialization. Optimization requires precise control over electrode geometry and electrical contacts, areas where 6CCVD excels:

Research Requirement	6CCVD Customization Capability	Value Proposition
Electrode Size (42 cm²)	Custom dimensions and large-area plates up to 125mm (PCD/BDD).	Enables immediate scale-up from lab-scale 42 cm² cells to pilot and industrial flow reactors.
Electrical Contact	Internal metalization services (Au, Pt, Pd, Ti, W, Cu).	Ensures robust, low-resistance electrical contacts essential for high current density operation and minimizing ohmic losses, thereby reducing SEC.
Thickness Control	SCD/PCD thickness from 0.1 µm to 500 µm.	Allows engineers to specify optimal BDD film thickness for balancing performance, lifetime, and material cost.
Surface Finish	Polishing capability (Ra < 5nm for inch-size PCD).	Provides smooth, uniform surfaces crucial for consistent current distribution and long-term electrode stability in aggressive chemical environments.

Engineering Support

6CCVD’s in-house PhD team specializes in diamond material science and electrochemical applications. We can assist researchers and engineers with:

Doping Optimization: Consulting on the precise boron doping concentration required to maximize the overpotential for oxygen evolution, thereby enhancing the production of highly oxidative hydroxyl radicals (·OH) over parasitic oxygen evolution (O₂).
Cell Design Integration: Providing material selection and design consultation for integrating large-area BDD electrodes into high-throughput flow cells, specifically targeting the reduction of the high SEC observed in this HTC process water treatment project.
Global Logistics: Offering reliable global shipping (DDU default, DDP available) to ensure timely delivery of custom BDD electrodes worldwide.

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

Tech Support

Original Source

DOI: https://doi.org/10.1016/j.envres.2022.114773

References

2022 - A comprehensive review on current technologies for removal of endocrine disrupting chemicals from wastewaters [Crossref]
2012 - Electrochemical oxidation of succinic acid in aqueous solutions using boron doped diamond anodes [Crossref]
2015 - Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review [Crossref]
2009 - Electro-Fenton process and related electrochemical technologies based on Fenton’s reaction chemistry [Crossref]
2005 - Electrochemical oxidation of phenolic wastes with boron-doped diamond anodes
2021 - Electrochemical oxidation of organic pollutants in low conductive solutions
2021 - Electrochemically generated sulfate radicals by boron doped diamond and its environmental applications [Crossref]
2010 - Removal of acid green dye 50 from wastewater by anodic oxidation and electrocoagulation-A comparative study [Crossref]
2019 - Performance of electrochemical processes in the treatment of reverse osmosis concentrates of sanitary landfill leachate [Crossref]