Electrochemical oxidation using a boron doped diamond electrode as a water treatment process- removal of residual micropollutants and inac-tivation of microorganisms

At a Glance

Metadata	Details
Publication Date	2015-08-12
Journal	mediaTUM – the media and publications repository of the Technical University Munich (Technical University Munich)
Authors	Mohamad Rajab
Citations	1
Analysis	Full AI Review Included

Boron-Doped Diamond (BDD) Electrodes for Advanced Water Treatment: Micropollutant Degradation and Disinfection

Executive Summary

This technical analysis, based on research into Electrochemical Advanced Oxidation Processes (EAOPs) using Boron-Doped Diamond (BDD) electrodes, highlights BDD’s critical role in tertiary water treatment and disinfection.

Superior Oxidation Power: BDD anodes enable the in situ generation of highly potent reactive oxygen species (ROS), primarily hydroxyl radicals (•OH) and ozone (O₃), providing a robust, chemical-free Advanced Oxidation Process (AOP).
Rapid Contaminant Removal: Complete degradation of persistent micropollutants (Diclofenac, Sulfamethoxazole, Bisphenol A) in real Wastewater Treatment Plant (WWTP) effluent was achieved in minutes, demonstrating high kinetic efficiency.
Effective Disinfection: The BDD system achieved effective 5-6 log inactivation of the model organism Pseudomonas aeruginosa, driven by a synergistic effect of in situ generated ozone and free chlorine (in chloride-containing water).
Operational Optimization: Research confirms that current density (optimal range 100-200 mA cm^-2) is the key control parameter, balancing rapid degradation kinetics against energy consumption and the formation of inorganic disinfection by-products (DBPs) like chlorate and perchlorate.
Material Imperative: The study emphasizes that optimizing the nano-diamond structure and electrode design is crucial for enhancing ozone formation efficiency and mitigating DBP formation, directly aligning with 6CCVD’s MPCVD customization capabilities.

Technical Specifications

Parameter	Value	Unit	Context
Anode Material	Boron-Doped Diamond (BDD)	N/A	Used on Niobium (Nb) or Silicon (Si) substrates
Effective Anode Area Tested	12 to 24	cm²	Used in batch reactor setups (CONDIAPURE®)
Applied Current Density Range	42 to 333	mA cm^-2	Range tested for degradation and disinfection
SMX Removal Time (WWTP Effluent)	5	minutes	Achieved at 333 mA cm^-2
BPA Removal Time (WWTP Effluent)	15	minutes	Achieved at 208 mA cm^-2 (Q/V=430 mAh L^-1)
P. aeruginosa Inactivation Level	5-8	log units	Achieved depending on current density and chloride content
Energy Consumption (6-log inactivation)	0.3 to 0.6	kWh m^-3	Achieved at 167 mA cm^-2 in synthetic water
Ozone Concentration (High Current Density)	0.24	mg L^-1	Measured at 333 mA cm^-2 (WWTP effluent)
Perchlorate Concentration (Worst Case)	5.65	mg L^-1	Measured after 15 min treatment at 208 mA cm^-2 in WWTP effluent
BDD Potential Window	-1.25 to +2.8	V vs. SHE	Wide potential window enables strong oxidant generation

Key Methodologies

The experiments utilized electrochemical advanced oxidation processes (EAOPs) in batch recirculation mode to assess BDD electrode performance across various water matrices.

Electrode System: Conductive diamond electrode stacks (CONDIAS DIACHEM®) were employed, consisting of BDD anodes and cathodes deposited on Niobium (Nb) or Silicon (Si) substrates.
Reactor Design: Three reactor cells were used: a Glass reactor (92 cm³), CONDIAPURE® (45 cm³), and CONDIAPURE-SHORTY® (19 cm³), operating in a recirculation loop with controlled flow rates (up to 10 L min^-1).
Current Confinement: A Nafion cation exchange membrane was placed in direct contact with the BDD anode/cathode pair to create a gap-free sandwich structure, enhancing local current density and promoting efficient ozone formation even at low electrical conductivities.
Operational Conditions: All experiments were conducted at controlled room temperature (20 ± 1 °C or 25 ± 2 °C) and slightly alkaline pH (8.0-8.5).
Water Matrices Tested: Degradation kinetics were compared across Deionized (DI) water, Synthetic Hard Water (SW), Synthetic Water with Dissolved Organic Carbon (SW+DOC), and real secondary WWTP effluent.
Analytical Techniques:
- Transformation Products (TPs) were identified using serial coupling of Reversed-Phase (RP) and Zwitterionic Hydrophilic Interaction (ZIC-HILIC) LC-MS (TOF-MS) for comprehensive screening of polar and nonpolar compounds.
- Inorganic by-products (chlorate, perchlorate) were quantified using Ion Chromatography (IC).
- Ozone and free chlorine concentrations were monitored photometrically (Indigo method and DPD method, respectively).

6CCVD Solutions & Capabilities

The research confirms that Boron-Doped Diamond (BDD) is the optimal anode material for high-efficiency EAOPs, particularly in complex water matrices like industrial and municipal effluents. 6CCVD is uniquely positioned to supply the high-quality BDD materials and custom electrode configurations required to replicate, optimize, and scale this critical water treatment technology.

Applicable Materials

Application Requirement	6CCVD Material Solution	Technical Advantage
High-Efficiency EAOP Anodes	Boron-Doped Diamond (BDD)	High overpotential for oxygen evolution, maximizing hydroxyl radical and ozone generation (in situ AOP).
Custom Electrode Substrates	BDD on Niobium (Nb) or Titanium (Ti)	We provide BDD films deposited on customer-specified conductive substrates (Nb/Ti are standard for electrochemical applications).
Optimizing Nano-Structure	High-Quality MPCVD PCD	The study noted that optimizing the “nano-diamond structure” enhances ozone formation. 6CCVD offers precise control over grain size and morphology during MPCVD growth to meet specific electrochemical performance targets.
High Current Density Operation	Heavy Boron Doped PCD	Our highly conductive PCD material ensures low resistivity, crucial for maintaining high current densities (up to 333 mA cm^-2 and beyond) required for rapid degradation kinetics.

Customization Potential

The research utilized specific electrode areas (12 cm², 24 cm²) and noted the need for improved reactor hydrodynamics and upscaling. 6CCVD directly addresses these needs:

Custom Dimensions: We manufacture BDD plates and wafers up to 125mm in diameter, allowing researchers and engineers to transition from bench-scale (cm²) to pilot-scale (inch-size) systems seamlessly.
Custom Substrate Integration: We offer BDD deposition on various substrates (including Nb and Ti, as used in this study) and can provide custom laser cutting and shaping services to fit proprietary reactor geometries (e.g., flow-through cells, CONDIAPURE variants).
Metalization Services: While the study focused on the BDD surface, future reactor designs may require complex electrical contacts. 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) to ensure robust electrical connections and stack integration.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of CVD diamond. We offer expert consultation to researchers and industrial partners focusing on Electrochemical Water Treatment projects.

Material Selection: Assistance in selecting the optimal BDD doping level and morphology (PCD grain size) to balance high oxidant generation (hydroxyl radicals/ozone) with minimized DBP formation.
Upscaling Support: Consultation on designing BDD electrodes for continuous-flow systems, addressing the hydrodynamic and energy efficiency challenges identified in the dissertation.
Global Supply Chain: We ensure reliable, global shipping (DDU default, DDP available) of high-purity BDD electrodes, minimizing lead times for critical R&D and pilot projects worldwide.

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

View Original Abstract

A boron doped diamond electrode was tested for the removal of micropollutants and inactivation of microorganisms. The results showed that higher current densities accelerated the degradation process, whereas an increase in water complexity decelerated it. A current density between 100-200 mA cm-2 would completely remove micropollutants and limit the formation of inorganic by-products. A synergic effect of reactive oxygen and chlorine species assured the disinfection capability of the electrode.

Tech Support

Original Source

DOI: None