Electrochemical Oxidation of Organic Pollutants in Aqueous Solution Using a Ti4O7 Particle Anode

At a Glance

Metadata	Details
Publication Date	2023-05-17
Journal	Membranes
Authors	Andrey Kislyi, Ilya A. Moroz, Vera Guliaeva, Yuri Prokhorov, Anastasiia Klevtsova
Institutions	Kuban State University
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Electrochemical Oxidation Anodes

Reference Paper: Kislyi et al., Electrochemical Oxidation of Organic Pollutants in Aqueous Solution Using a $\text{Ti} _{4}\text{O} _{7}$ Particle Anode, Membranes 2023, 13, 521.

Executive Summary

This research validates the use of substoichiometric titanium oxide ($\text{Ti} _{4}\text{O} _{7}$) particle anodes for Electrochemical Advanced Oxidation Processes (EAOPs), directly benchmarking their performance against high-end diamond electrodes.

Application Focus: Successful anodic oxidation (AO) and mineralization of common organic pollutants (hydroquinone, benzoic, maleic, and oxalic acids) in aqueous solutions.
BDD Benchmark: The $\text{Ti} _{4}\text{O} _{7}$ anode is explicitly compared to Boron-Doped Diamond (BDD) anodes, confirming its classification as a high Oxygen Evolution Potential (OEP) “non-active” electrode material.
High Efficiency: Achieved a high instantaneous current efficiency (ICE) of approximately 40% and a pollutant removal degree exceeding 99%.
Stability Demonstrated: The $\text{Ti} _{4}\text{O} _{7}$ particle anode maintained good stability over 108 operating hours at a high current density of 36 $\text{mA}/\text{cm} ^{2}$.
Material Comparison: While $\text{Ti} _{4}\text{O} _{7}$ offers a low-cost alternative, the study reinforces the need for high-OEP materials like BDD to maximize hydroxyl radical ($\text{HO} ^{\bullet}$) generation for complete mineralization.
Methodology: Utilized a novel particle-bed flow cell design, demonstrating effective mass transfer control for organic degradation kinetics.

Technical Specifications

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

Parameter	Value	Unit	Context
Anode Material	$\text{Ti} _{4}\text{O} _{7}$	N/A	Substoichiometric Titanium Oxide
Anode Granule Size	1-3	mm	Used in particle bed flow cell
Internal Pore Size (Granules)	$\approx 1$	µm	Facilitates sorption and mineralization
Initial COD Concentration ($\text{COD} _{0}$)	600	$\text{mg}/\text{L}$	Total organic load
Maximum Applied Current Density	36	$\text{mA}/\text{cm} ^{2}$	Continuous mode
Maximum Instantaneous Current Efficiency (ICE)	$\approx 40$	%	Measured at 36 $\text{mA}/\text{cm} ^{2}$
Pollutant Removal Degree	>99	%	Achieved for most organics
Oxalic Acid Mineralization	Complete	N/A	Achieved after 4 hours
Anode Stability Duration	108	hours	Tested at 36 $\text{mA}/\text{cm} ^{2}$
Cathode Material	Platinized Titanium	N/A	Coating thickness 5.0 µm
Supporting Electrolyte	0.1 M $\text{Na} _{2}\text{SO} _{4}$	M	Sodium Sulfate

Key Methodologies

The experiment utilized a specialized electrochemical flow cell (EC-FC) and precise operational control to evaluate the $\text{Ti} _{4}\text{O} _{7}$ particle anode:

Electrochemical Cell Design: A plate electrolysis chamber was constructed using Polytetrafluoroethylene (PTFE) casing, featuring a porous particle anode and a rhomboid grid cathode (platinized titanium).
Anode Configuration: $\text{Ti} _{4}\text{O} _{7}$ granules (1-3 mm) were packed to form a 10 mm thick anode layer (approx. 110 g weight). A 3 mm thick polypropylene separator divided the anode and cathode.
Solution Parameters: Model solutions of hydroquinone, benzoic acid, maleic acid, and oxalic acid were prepared with an initial COD of 600 $\text{mg}/\text{L}$, using 0.1 M $\text{Na} _{2}\text{SO} _{4}$ as the supporting electrolyte.
Flow Regime: Experiments were conducted in a continuous recirculation mode from a 0.5 L reservoir, testing total flow rates from 110 to 1100 $\text{mL}/\text{min}$.
Current Modes: Both continuous DC current (9, 18, and 36 $\text{mA}/\text{cm} ^{2}$) and pulsed current modes (1 $\text{min}/1 \text{min}$ and 5 $\text{s}/5 \text{s}$ pulse/pause cycles) were investigated to optimize oxidation kinetics.
Characterization: Anode composition and phase purity were confirmed using X-ray powder diffraction (XRD). Surface morphology and elemental analysis (fouling) were assessed using Field Emission Scanning Electron Microscopy (SEM-EDS) and Fourier-Transform Infrared Spectroscopy (FT-IR).

6CCVD Solutions & Capabilities

The research confirms that high Oxygen Evolution Potential (OEP) anodes are essential for efficient EAOPs, explicitly referencing Boron-Doped Diamond (BDD) as the performance benchmark. 6CCVD specializes in MPCVD diamond materials that meet and exceed the requirements for next-generation electrochemical systems.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage
High OEP Anode Material	Boron-Doped Diamond (BDD) Wafers/Plates.	BDD is the industry standard for “non-active” anodes, offering the highest OEP and unparalleled chemical stability, ensuring maximum $\text{HO} ^{\bullet}$ generation and complete mineralization, superior to $\text{Ti} _{4}\text{O} _{7}$ in long-term performance.
Scale-Up & High-Throughput	Custom Polycrystalline Diamond (PCD) Plates up to 125mm.	While the paper used particle beds, 6CCVD provides large-area, high-conductivity PCD plates (up to 125 mm diameter). This enables high-flux flow-through reactor designs, eliminating the pressure drop and packing issues inherent to particle electrodes.
Electrode Thickness Control	SCD/PCD Thickness Control (0.1µm - 500µm).	We offer precise control over the diamond layer thickness, allowing engineers to optimize the active surface area and conductivity for specific current density requirements (e.g., 36 $\text{mA}/\text{cm} ^{2}$ and higher).
Integrated Electrode Assemblies	Custom Metalization Services (Ti, Pt, Au, Pd, Cu).	The paper utilized a platinized titanium cathode. 6CCVD offers in-house metalization capabilities, allowing for the direct deposition of contact layers (e.g., Ti/Pt/Au) onto BDD substrates, creating robust, integrated electrode stacks for complex EC-FC designs.
Fouling Mitigation	Ultra-Smooth Polishing (SCD Ra < 1nm, PCD Ra < 5nm).	Polished BDD surfaces minimize the physical adsorption and polymerization fouling observed in porous/particle electrodes, maintaining efficiency and reducing the need for electrode regeneration.

Engineering Support

6CCVD’s in-house PhD team provides expert consultation on material selection and design optimization for advanced electrochemical applications, including EAOPs, water treatment, and sensor development. We assist researchers in transitioning from benchmark materials like $\text{Ti} _{4}\text{O} _{7}$ to high-performance, scalable BDD systems.

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

View Original Abstract

Anodes based on substoichiometric titanium oxide (Ti4O7) are among the most effective for the anodic oxidation of organic pollutants in aqueous solutions. Such electrodes can be made in the form of semipermeable porous structures called reactive electrochemical membranes (REMs). Recent work has shown that REMs with large pore sizes (0.5-2 mm) are highly efficient (comparable or superior to boron-doped diamond (BDD) anodes) and can be used to oxidize a wide range of contaminants. In this work, for the first time, a Ti4O7 particle anode (with a granule size of 1-3 mm and forming pores of 0.2-1 mm) was used for the oxidation of benzoic, maleic and oxalic acids and hydroquinone in aqueous solutions with an initial COD of 600 mg/L. The results demonstrated that a high instantaneous current efficiency (ICE) of about 40% and a high removal degree of more than 99% can be achieved. The Ti4O7 anode showed good stability after 108 operating hours at 36 mA/cm2.

Tech Support

Original Source

DOI: https://doi.org/10.3390/membranes13050521

References

2018 - Electrochemical Oxidation of Organic Pollutants for Wastewater Treatment [Crossref]
2018 - Electrochemical Treatment of Real Wastewater. Part 1: Effluents with Low Conductivity [Crossref]
2017 - Electrochemical Oxidation of COD from Real Textile Wastewaters: Kinetic Study and Energy Consumption [Crossref]
2023 - Wastewater Treatment by Anodic Oxidation in Electrochemical Advanced Oxidation Process: Advance in Mechanism, Direct and Indirect Oxidation Detection Methods [Crossref]
2021 - Advanced Electrochemical Oxidation Processes in the Treatment of Pharmaceutical Containing Water and Wastewater: A Review [Crossref]
2021 - Anodic Oxidation for the Degradation of Organic Pollutants: Anode Materials, Operating Conditions and Mechanisms. A Mini Review [Crossref]
1997 - Theoretical Model for the Anodic Oxidation of Organics on Metal Oxide Electrodes [Crossref]
2023 - A Critical Review on Latest Innovations and Future Challenges of Electrochemical Technology for the Abatement of Organics in Water [Crossref]
2009 - Direct and Mediated Anodic Oxidation of Organic Pollutants [Crossref]
2018 - Electro-Oxidation of Organic Pollutants by Reactive Electrochemical Membranes [Crossref]