Boron-doped Diamond Surface Research Articles

Protein adsorption behavior on reduced graphene oxide and boron-doped diamond investigated by electrochemical impedance spectroscopy

As advanced and promising carbon materials, we found reduced graphene oxide (rGO) and boron-doped diamond (BDD) demonstrated special impedance response regarding protein adsorption compared with other materials. According to the results of electrochemical impedance spectroscopy (EIS), rGO showed two time constants (two semicircles in Nyquist plot) when exposed to model protein bovine serum albumin (BSA) solutions; BDD showed decreased impedance response when exposed to high concentration of BSA. They demonstrated special but different impedance response upon BSA adsorption. Based on fitting results of EIS data and hypothesis of protein adsorption, protein adsorption model on the interface of protein solution and carbon electrode surfaces have been established, which is applicable to rGO and BDD surface, and is further expected to be applicable to other carbon materials. Besides the in-depth understanding of protein adsorption behavior, this study also indicates a potential way to control the orientations of protein molecules on solid surface.

Deoxyribonucleic-acid-sensitive Polycrystalline Diamond Solution-gate Field-effect Transistor with a Carboxyl-terminated Boron-doped Channel.

This paper describes a deoxyribonucleic-acid-sensitive electrolyte solution-gate field-effect transistor (SGFET) sensor utilizing a partial carboxyl-terminated boron-doped polycrystalline diamond surface as a linker to connect a deoxyribonucleic acid (DNA) probe. A high density of carboxyl termination on the polycrystalline diamond surface that was employed as a FET channel was achieved using a vacuum ultraviolet system with oxygen gas. A single-stranded DNA probe was immobilized on the polycrystalline diamond channel via amino coupling. The current-voltage characteristics of the polycrystalline diamond SGFET sensor was examined with bias voltages within its potential voltage window. The characteristics of the drain-source current verses the drain-source voltage showed a pinch-off, a shift voltage of up to 40 mV with a coefficient of variation of 4 - 11% was obtained between hybridization and denaturation. In addition, a single nucleotide mutation of DNA sequence was selectively recognized by the shift voltage up to ca. 10 mV.

Switchable Product Selectivity in the Electrochemical Reduction of Carbon Dioxide Using Boron-Doped Diamond Electrodes.

The main product obtained by electrochemical reduction of CO2 depends on the electrode material, and in many cases the Faradaic efficiency for this is determined by the electrolyte. Only a few investigations in which attempts to produce different products from the same electrode material have been done so far. In this work, we focus on boron-doped diamond (BDD) electrodes with which plentiful amounts of formic acid and small amounts of carbon monoxide have been produced. By optimizing certain parameters and conditions used in the electrochemical process with BDD electrodes, such as the electrolyte, the boron concentration of the BDD electrode, and the applied potential, we were able to control the selectivity and efficiency with which carbon monoxide is produced. On one hand, with a BDD electrode with 1% boron used for the cathode and KClO4 for the catholyte, the selectivity for producing carbon monoxide was high. On the other hand, with a BDD electrode with 0.1% boron used for the cathode and KCl for the catholyte, the production of formic acid was the most evident. In situ attenuated total reflectance-infrared (ATR-IR) measurements during electrolysis showed that CO2•- intermediates were adsorbed on the BDD surface in the KClO4 aqueous solution. Here, switchable product selectivity was achieved when reducing CO2 using BDD electrodes.

BDD electrodes modified with metal nano-catalysts for coffee discrimination in real samples

An amperometric sensory approach based on boron-doped diamond (BDD) electrodes decorated with transition metals nano-catalysts was assessed for coffee discrimination in real samples. Thus, a bare BDD electrode along with four BDD electrodes modified respectively with Platinum/Iridium (PtIr), Platinum/Gold (PtAu), Gold/Ruthenium (AuRu) and Ruthenium (Ru) were investigated altogether in a broadly selective electrode array configuration to detect electro-active species in coffee samples. The transition metal nanoparticles were deposited onto BDD by sputtering thin metal layers onto polycrystalline BDD by a physical vapor deposition method, followed by a heat treatment at 700 °C under oxygen-free atmosphere. Such as process led to stable populations of strongly adherent nanosized metal particles over BDD surfaces as characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. Chemometric analysis was adopted to examine the relevant parameters of the amperometric detection for classifying four coffee capsule samples. Promising results were obtained towards a new sensor technology to artificially predict taste for foodstuff analysis.

Electrochemical Pinacol Coupling of Acetophenone Using Boron‐Doped Diamond Electrode

AbstractAn electrochemical pinacol coupling reaction of acetophenone using a boron‐doped diamond (BDD) electrode has been reported. This transformation is driven by the one‐electron reduction of acetophenone on the BDD cathode, followed by an intermolecular radical coupling. Owing to the BDD's outstanding electrochemical properties, the pinacol‐type compound has been obtained in good conversion yield. The roles of a supporting electrolyte and solvent were addressed; (1) lithium ions contribute to increase in the reactivity of the radical intermediate. (2) Addition of water promotes the electron transfer process at the BDD surface. The reaction is relatively tolerant to para‐substituted acetophenone derivatives. Since electric current is directly employed as reducing reagents to generate a radical intermediate, the reaction is metal‐free, sustainable, and inherently safe.

Modification of boron-doped diamond electrodes with platinum-iridium for carbon dioxide electroreduction

Boron-doped diamond (BDD) is reportedly a good electrode material for the electroreduction of CO2 to produce formaldehyde with high Faradaic efficiency. In this study, BDD electrodes were modified with a platinum-iridium composite (Pt-Ir). Deposition of Pt-Ir on the surface of BDD was performed by two different methods. One method involved the modification of the BDD surface, wherein terminal-H atoms were substituted with N atoms. The N-terminal BDD was then immersed in a Pt–Ir nanoparticle solution to form Pt–Ir–BDD (1). The Pt–Ir nanoparticles were synthesized from a 3:4 molar ratio mixture of H2PtCl6 and K2IrCl6 by a hydrothermal method. Characterization of Pt–Ir nanoparticles by using UV-Vis spectrophotometry and Transmission Electron Microscopy (TEM) image showed an absorbance peak at 420 nm with an average particle size of 2.6±0.6 nm. In the second method, Pt-Ir was deposited onto BDD using chemically assisted electrodeposition by applying a reduction potential of −0.5 V (vs. Ag/AgCl) to form Pt–Ir–BDD (2). Scanning Electron Microscope (SEM) images showed that the second method provides better distribution of Pt–Ir on the BDD surface. Furthermore, cyclic voltammetry of CO2, dissolved in 0.1 M NaCl showed a reduction potentials at −1.7, −1.3, and −1.2 V (vs. Ag/AgCl) at BDD, Pt–Ir–BDD (1) and Pt– Ir–BDD (2), respectively, indicating that modification with Pt–Ir allows the conversion of CO2 with higher Faradaic efficiency.

A boron-doped diamond electrode decorated with hemoglobin-modified platinum nanoparticles as a biosensor for acrylamide detection

Acrylamide (AA) is a neurotoxin and potential carcinogen. It has been found in various thermally processed foods, e.g., potato chips and biscuits. Thus, simple, rapid, and sensitive methods for AA detection are needed to ensure food safety. Herein, the fabrication of a highly stable AA biosensor is presented. A boron-doped diamond (BDD) was modified by Pt and hemoglobin. In the first step, platinum nanoparticles (Pt NPs) were chemically seeded onto the BDD surface using NaBH as a reducing agent. The electrochemical overgrowth of these Pt NP seeds was conducted at a constant potential of −0.2 V in a 1 mM Pt solution. Then, rapid thermal annealing (RTA) of the BDD/Pt NP composite was conducted at 700 °C under N atmosphere to enhance its stability. After RTA, BDD/Pt NP was electrochemically activated between −0.5 and 1.5 V. Then, further overgrowth was performed using a deposition voltage of −0.2 V to renew the BDD/Pt NP surface. Finally, 0.15-mM hemoglobin was used to modify BDD/Pt NP. The characterization of the resulting surface was performed using scanning electron microscopy. The biosensor exhibited an optimal response (limit of detection = 0.012 nM) at pH 4.9 in a 0.2-M acetate buffer solution.

Removal of the drug procaine from acidic aqueous solutions using a flow reactor with a boron-doped diamond anode

This article reports the electrochemical advanced oxidation treatment of 2.5 L of acidic aqueous solutions with 0.320 mM of the drug procaine hydrochloride in 0.050 M Na2SO4 using a pre-pilot flow plant. This was equipped with a cell, containing a boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 generation, which was connected to an annular photoreactor with a 160 W UVA lamp for the study of photoelectro-Fenton (PEF) process. Poor degradation and mineralization was attained by electrochemical oxidation with electrogenerated H2O2 due to the limited attack of both, hydroxyl radical (OH) formed at the BDD surface from water oxidation and H2O2 on organic matter. The electro-Fenton process became more effective thanks to the simultaneous oxidation with OH formed from Fenton’s reaction in the presence of Fe2+. The most powerful process was PEF because of the additional photolysis of photoactive intermediates by UVA radiation. This method allowed achieving 91% mineralization after 360 min of electrolysis at 33.3 mA cm−2. The effect of current density and drug concentration on PEF performance was examined. The mineralization current efficiency and energy consumption were determined for each treatment. Two N-containing derivatives were identified by gas chromatography-mass spectrometry. The quantification of generated carboxylic acids revealed that the final solution in PEF was composed of a mixture of acetic and formic acids.

Enhancing Electrochemical Efficiency of Hydroxyl Radical Formation on Diamond Electrodes by Functionalization with Hydrophobic Monolayers.

Electrochemical formation of high-energy species such as hydroxyl radicals in aqueous media is inefficient because oxidation of H2O to form O2 is a more thermodynamically favorable reaction. Boron-doped diamond (BDD) is widely used as an electrode material for generating •OH radicals because it has a very large kinetic overpotential for O2 production, thus increasing electrochemical efficiency for •OH production. Yet, the underlying mechanisms of O2 and •OH production at diamond electrodes are not well understood. We demonstrate that boron-doped diamond surfaces functionalized with hydrophobic, polyfluorinated molecular ligands (PF-BDD) have significantly higher electrochemical efficiency for •OH production compared with hydrogen-terminated (H-BDD), oxidized (O-BDD), or poly(ethylene ether)-functionalized (E-BDD) boron-doped diamond samples. Our measurements show that •OH production is nearly independent of surface functionalization and pH (pH = 7.4 vs 9.2), indicating that •OH is produced by oxidation of H2O in an outer-sphere electron-transfer process. In contrast, the total electrochemical current, which primarily produces O2, differs strongly between samples with different surface functionalizations, indicating an inner-sphere electron-transfer process. X-ray photoelectron spectroscopy measurements show that although both H-BDD and PF-BDD electrodes are oxidized over time, PF-BDD showed longer stability (≈24 h of use) than H-BDD. This work demonstrates that increasing surface hydrophobicity using perfluorinated ligands selectively inhibits inner-sphere oxidation to O2 and therefore provides a pathway to increased efficiency for formation of •OH via an outer-sphere process. The use of hydrophobic electrodes may be a general approach to increasing selectivity toward outer-sphere electron-transfer processes in aqueous media.

Heterogeneous oxidation of highly boron-doped diamond electrodes and its influence on the surface distribution of electrochemical activity

The electrochemical active surface area (EASA) of polycrystalline boron-doped diamond (BDD) electrodes is heterogeneous and can be affected by numerous factors. There is a strong need for proper consideration of BDD heterogeneity in order to improve this material's range of application in electrochemistry. Localized changes in surface termination due to the influence of oxidation agent result in increased surface resistance. The observed behavior of this characteristic feature varies among individual grains, depending on their crystallographic orientation. Still, there is not much information about this key factor in terms of its influence on the electrochemical response of BDD. In this study we compared two approaches towards BDD surface oxidation, namely: anodic polarization at potentiostatic and potentiodynamic conditions. The surface impedance measurements via Nanoscale Impedance Microscopy (NIM) allowed the confirmation of diversified propensity for the modification of surface termination in BDD. We showed that the NIM studies provide a deep understanding on the electrical characterization and variation of surface resistance in BDD electrodes. In order to evaluate the actual heterogeneity of electrochemical activity distribution, voltammetry, dynamic electrochemical impedance spectroscopy (DEIS) and scanning electrochemical microscopy (SECM) studies were performed. For each investigated electrode, departure from the Randles-Sevcik equation was observed, with its level depending on the surface heterogeneity and oxidation treatment, justifying the standardization of pre-treatment procedure and development of non-standard model for diffusion transport in proximity of BDD electrode.

Laser-Induced Periodic Surface Structures (LIPSS) on Heavily Boron-Doped Diamond for Electrode Applications.

Diamond is known as a promising electrode material in the fields of cell stimulation, energy storage (e.g., supercapacitors), (bio)sensing, catalysis, etc. However, engineering its surface and electrochemical properties often requires costly and complex procedures with addition of foreign material (e.g., carbon nanotube or polymer) scaffolds or cleanroom processing. In this work, we demonstrate a novel approach using laser-induced periodic surface structuring (LIPSS) as a scalable, versatile, and cost-effective technique to nanostructure the surface and tune the electrochemical properties of boron-doped diamond (BDD). We study the effect of LIPSS on heavily doped BDD and investigate its application as electrodes for cell stimulation and energy storage. We show that quasi-periodic ripple structures formed on diamond electrodes laser-textured with a laser accumulated fluence of 0.325 kJ/cm2 (800 nm wavelength) displayed a much higher double-layer capacitance of 660 μF/cm2 than the as-grown BDD (20 μF/cm2) and that an increased charge-storage capacity of 1.6 mC/cm2 (>6-fold increase after laser texturing) and a low impedance of 2.74 Ω cm2 turn out to be appreciable properties for cell stimulation. Additional morphological and structural characterization revealed that ripple formation on heavily boron-doped diamond (2.8 atom % [B]) occurs at much lower accumulated fluences than the 2 kJ/cm2 typically reported for lower doping levels and that the process involves stronger graphitization of the BDD surface. Finally, we show that the exposed interface between sp2 and sp3 carbon layers (i.e. the laser-ablated diamond surface) revealed faster kinetics than the untreated BDD in both ferrocyanide and RuHex mediators, which can be used for electrochemical (bio)sensing. Overall, our work demonstrates that LIPSS is a powerful single-step tool for the fabrication of surface-engineered diamond electrodes with tunable material, electrochemical, and charge-storage properties.

Nanopyramid boron-doped diamond electrode realizing nanomolar detection limit of 4-nonylphenol

In this paper, a nanopyramid boron-doped diamond (BDD) electrode is prepared by hydrogen-plasma treating conventional chemical vapor deposition BDD films. The nanopyramid grains are formed by a vaporization and secondary nucleation on BDD surface to test the trace level of an environmental hormone pollutant of 4-nonylphenol (4-NP). Voltammetry of 4-NP investigated on this electrode reveals the irreversible, adsorption-controlled, one-electron-and-one-proton involved oxidation process. The oxidation peak current is significantly evident even at low concentration of 4-NP (in the region of 1–100 nM) and the detection limit can be realized as low as 0.26 nM, which is lower than most previous reports. It is attributed to the more reaction sites provided by the high dense nanopyramids on the BDD surface and the hydrogen-terminated surface. Moreover, the electrode is reusable for the physical adsorption between 4-NP molecule and nanopyramid BDD. Taking into considering the unique properties of BDD, the corresponding electrodes show stability and specificity for detecting trace 4-NP molecules.

Ensuring the overall combustion of herbicide metribuzin by electrochemical advanced oxidation processes. Study of operation variables, kinetics and degradation routes

This article reports the electrochemical degradation of the herbicide metribuzin (MTZ) in sulfate medium by advanced oxidation processes like anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF). A boron-doped diamond (BDD) anode was combined with an air-diffusion cathode with ability to produce H2O2. Unprecedented overall combustion was feasible by all methods at a constant current density (j) ≥100.0 mA cm−2. The total organic carbon (TOC) removal achieved by AO-H2O2 was independent from pH within the range 3.0–9.0, whereas the oscillatory dependence of the pseudo-first-order MTZ decay rate constant with this variable was ascribed to adsorption on the BDD surface. In EF and PEF at pH 3.0, 0.50 mM Fe2+ was determined as optimum catalyst content and the MTZ removal showed two consecutive pseudo-first-order kinetic stages. These were related to the fast reaction of the target molecule with OH formed from Fenton’s reaction, followed by a slower attack of physisorbed BDD(OH) onto Fe(III)-MTZ complexes. The effect of j and MTZ content on decay kinetics and TOC removal was examined. PEF was the best treatment due to the decomposition of photoactive intermediates by UVA radiation, yielding total mineralization of a 0.523 mM herbicide solution after 420 min of electrolysis at 100.0 mA cm−2. A thorough reaction pathway for MTZ degradation is proposed from the sixteen heteroaromatic by-products and three aliphatic molecules identified by GC–MS and LC-MS/MS. Oxalic and oxamic acids were detected as final carboxylic acids by ion-exclusion HPLC.

Electrochemical self-cleaning anodic surfaces for biofouling control during water treatment

Biofilm formation and growth on submerged surfaces causes numerous operational problems, ranging from hindering diffusion of pollutants to electrode surfaces during electrochemical water treatment to harboring pathogens in indoor plumbing. This work evaluates electrochemical biofilm dispersion kinetics from boron-doped diamond (BDD) surfaces in situ using optical coherence tomography microscopy to track the volume of biofilm (biovolume) on the electrode. After starting with a 75 μm thick biofilm, applying 50 mA cm−2 results in near complete biofilm removal after 60 min, with a pseudo first-order biovolume removal rate of 0.023 min−1; higher applied currents had negligible additional benefits. Thus, it appears plausible to attain biofouling mitigation through electrochemical self-cleaning of BDD electrodes, potentially via the following two-step process: 1) hydroxyl radical production on the electrode surface which oxidizes polysaccharides or other cellular materials that attach bacteria to surface, followed by 2) gas evolution on the electrode surface (beneath the biofilm), which pushes and sloughs off the biofilm. This novel approach to biofouling management can find applications in electrochemical water treatment and other important surfaces (e.g., electrodes, membrane spacers, heat exchange surfaces, interior pipe surfaces, etc.) in water treatment systems where biofilms develop and harbor microbial pathogens.

Charge transfer/mass transport competition in advanced hybrid electrocatalytic wastewater treatment: Development of a new current efficiency relation

The contribution of homogeneous versus heterogeneous catalytic oxidation has been studied for the first time in a hybrid anodic oxidation (AO)/electro-Fenton (EF) batch reactor at different initial organic load in terms of chemical oxygen demand (COD) values of 1.61, 12.1 and 23.3 g-O2 L−1. The rate of three (electro)-chemical processes, e.g., (i) AO at the surface of boron-doped diamond (BDD) anode, (ii) Fenton oxidation in the bulk solution and (iii) mediated oxidation (MO) in the bulk solution, have been considered in a mathematical model. The mass transfer coefficient was depending on the concentration of the compound due to the unstationary behavior in the diffusion layer at the vicinity of the anode. After calibration and validation of the model with experimental data, it could be noticed that the competition between the mass transport and the charge transfer was evolving according to the COD load. At 1.61 g-O2 L−1, the applied current density was higher than the limiting current density all along the treatment, meaning that the process was under mass transport control. In this case, the Fenton oxidation rate had the highest contribution in the oxidation efficiency while AO oxidation rate had the lowest efficiency. Increasing the initial COD concentration up to 23.3 g-O2 L−1, made raising the influence of AO process that became predominant after a certain electrolysis time, before reaching the critical time (tcr). Finally, a new current efficiency expression has been proposed by taking into account the three reaction rates and the model could fit the experimental data, showcasing a promising approach. These results further emphasized the need to adapt the reactor design to favor either AO and/or Fenton oxidation according to the organic load of wastewater to be treated, i.e., as pre-treatment or polishing treatment.

Facet‐Resolved Electrochemistry of Polycrystalline Boron‐Doped Diamond Electrodes: Microscopic Factors Determining the Solvent Window in Aqueous Potassium Chloride Solutions

AbstractA systematic examination of the microscopic factors affecting the aqueous solvent (electrolyte) window of polycrystalline (p) boron‐doped diamond (BDD) electrodes in chloride‐containing salt solutions is undertaken by using scanning electrochemical cell microscopy (SECCM) in conjunction with electron backscatter diffraction (EBSD) and Raman microscopy. A major focus is to determine the effect of the local boron doping level, within the same orientation grains, on the solvent window response. EBSD is used to select the predominant (110) orientated areas of the surface with different boron‐doped facets, thereby eliminating crystallographic effects from the electrochemical response. Voltammetric SECCM is employed, whereby a cyclic voltammogram is recorded at each pixel mapped by the meniscus‐contact SECCM cell. The data obtained can be played as an electrochemical movie of potential‐resolved current maps of the surface to reveal spatial variations of electroactivity, over a wide potential range, including the solvent (electrolyte) window. Local heterogeneities are observed, indicating that the solvent window is mainly linked to local dopant levels, with lower dopant levels leading to a wider window, that is, slower electrode kinetics for solvent/electrolyte electrolysis. Furthermore, the effects of O‐ and H‐surface termination of the BDD surface are investigated for the same electrode (in the same area). The surface termination is a particularly important factor: the solvent window of an H‐terminated surface is wider than for O‐termination for similar boron dopant levels. Furthermore, the anodic potential window of the O‐terminated surface is greatly diminished due to chloride electro‐oxidation. These studies provide new perspectives on the local electrochemical properties of BDD and highlight the importance of probing the electrochemistry of BDD at the level of a single crystalline grain (facet) to unravel the factors that control the solvent (aqueous) window of these complex heterogeneous electrodes.

Role of Carboxyl and Amine Termination on a Boron-Doped Diamond Solution Gate Field Effect Transistor (SGFET) for pH Sensing.

In this paper, we report on the effect of carboxyl- and amine terminations on a boron-doped diamond surface (BDD) in relation to pH sensitivity. Carboxyl termination was achieved by anodization oxidation in Carmody buffer solution (pH 7). The carboxyl-terminated diamond surface was exposed to nitrogen radicals to generate an amine-terminated surface. The pH sensitivity of the carboxyl- and amine-terminated surfaces was measured from pH 2 to pH 12. The pH sensitivities of the carboxyl-terminated surface at low and high pH are 45 and 3 mV/pH, respectively. The pH sensitivity after amine termination is significantly higher—the pH sensitivities at low and high pH are 65 and 24 mV/pH, respectively. We find that the negatively-charged surface properties of the carboxyl-terminated surface due to ionization of –COOH causes very low pH detection in the high pH region (pH 7–12). In the case of the amine-terminated surface, the surface properties are interchangeable in both acidic and basic solutions; therefore, we observed pH detection at both low and high pH regions. The results presented here may provide molecular-level understanding of surface properties with charged ions in pH solutions. The understanding of these surface terminations on BDD substrate may be useful to design diamond-based biosensors.

Chemical modification of diamond surface by a donor–acceptor organic chromophore (P1): Optimization of surface chemistry and electronic properties of diamond

The first systematic study of P1-dye attachment to the surface of H-terminated boron-doped diamond (BDD) surface was carried out. Details about surface anchoring chemistry were explored on model nanodiamond particles. The electronic properties of boron doped diamond films were tuned from semiconducting to quasi-metallic ones. The relevant materials were analyzed by advanced chemical analysis, zeta-potential, IR and TEM (nanoparticles), Raman, XPS, AFM, SEM, Hall-effect and by in-depth photo/electrochemical studies (films). An improved photochemical grafting protocol was developed leading to a factor of 3 enhancement in photocurrent on comparable diamond electrodes. The champion electrode provided at 1 sun illumination a photocurrent of 6.6μAcm−2 which is the best value ever reported for a flat BDD electrode.

Evidence for the production of hydroxyl radicals at boron-doped diamond electrodes with different sp3/sp2 ratios and its relationship with the anodic oxidation of aniline

In this work, the electrochemical production of hydroxyl radicals on boron-doped diamond (BDD) electrodes with different sp3/sp2 ratios was studied, together with the relationship between the level of production of hydroxyl radicals and the degradation and mineralization of aniline, taken as a model organic compound. A higher sp3/sp2 ratio on the BDD surface produces a greater number of hydroxyl radicals, as previously stated; however, for the first time the difference in the production of hydroxyl radicals for different levels of sp2-impurities on BDD surface was established and its importance in determining the nature of the BDD surface (semi-active or inactive) is demonstrated. The results are of great relevance in interpreting the real effect of conductive diamond electrochemical oxidation on the treatment of organic wastes described in the literature.

Applicability of electrochemical methods to paper mill wastewater for reuse. Anodic oxidation with BDD and TiRuSnO2 anodes

The electrochemical oxidation of paper mill wastewater belonging from Halfa industries (Tunisia) was performed by galvanostatic electrolysis using boron-doped diamond (BDD) anodes and Ti-Ru-Sn ternary oxide (TiRuSnO2). The effect of several operating parameters, such as applied current density, flow rate, temperature, initial pH value and addition of NaCl was evaluated. Chemical oxygen demand (COD) and ammonium measurements were carried out to study the treatment of the actual wastewater. The energy consumption analysis has been also discussed. The experimental results exhibited that galvanostatic electrolyses with BDD always allowed efficient COD removal in any conditions thanks to the reaction with hydroxyl radicals electrogenerated on BDD surface during electrolysis. On the contrary, using the TiRuSnO2 anode, the complete COD removal was only obtained in the presence of chloride ions. Comparison of the results of the two electrodes showed that BDD provided a faster removal with higher efficiency and lower energy consumption, while TiRuSnO2 was more efficient for ammonium removal.