BDD Electrode Research Articles

The Removal of Organic Pollutants and Ammonia Nitrogen from High-Salt Wastewater by the Electro-Chlorination Process and Its Mechanism

Electro-chlorination (E-Cl) is an emerging and promising electrochemical advanced oxidation technology for wastewater treatment with the advantages of high efficiency, deep mineralization, a green process, and easy operation. It was found that the mechanism of pollutant removal by electro-chlorination mainly involves an indirect oxidation process, in which pollutant removal is mainly driven by the intermediate active species, especially RCS and chlorine radicals, with a strong oxidization ability produced at the anodes. In this work, we summarized the principles and pathways of the removal/degradation of pollutants (organic pollutants and ammonia nitrogen) by E-Cl and the major affecting factors including the applied current density, voltage, electrolyte concentration, initial pH value, etc. In the E-Cl system, the DSA and BDD electrodes were the most widely used electrode materials. The flow-through electrode reactor was considered to be the most promising reactor since it had a high porosity and large pore size, which could effectively improve the mass transfer efficiency and electron transfer efficiency of the reaction. Of the many detection methods for chlorine radicals and RCS, electron paramagnetic resonance (EPR) and spectrophotometry with N, N-diethyl-1,4-phenylenediamine sulfate (DPD) as the chromogenic agent were the two most widely used methods. Overall, the E-Cl process had excellent performance and prospects in treating salt-containing wastewater.

Mechanism and Process Optimization in the Electrooxidation of Oxalic Acid Using BDD Electrode under Nitric Acid Environment

Mechanism and Process Optimization in the Electrooxidation of Oxalic Acid Using BDD Electrode under Nitric Acid Environment

Electrochemical determination of nitazoxanide in environmental and pharmaceutical samples using a boron-doped diamond electrode

Consumption of Nitazoxanide (NTZ), a compound belonging to the class of nitrothiazoles, has increased due to its efficiency in treating viral gastroenteritis caused by rotavirus and norovirus “coronavirus disease”. Thus, developing a method capable of monitoring NTZ in wastewater and pharmaceutical formulations is relevant to human health control. However, most methods for NTZ determination are expensive and time-consuming. Hence, we present a fast, efficient, and low-waste method for NTZ monitoring in drugs and water samples using a boron-doped diamond electrode. A 3D-printed electrochemical cell with a capacity of 2 mL was used for all studies. Besides the simplicity of low waste generation, the method provided good analytical performance with a linear range of 2.0–20.0 µmol/L of NTZ, and a limit of detection (LOD) of 0.57 µmol/L. Recovery percentages between 99 and 107 % were obtained to analyze spiked samples. In addition, we demonstrate that the LOD value can be significantly improved by 50 times after applying a pre-concentration step using solid-phase extraction. Therefore, we believe the described approach is a simple and efficient electrochemical method for monitoring NTZ levels in pharmaceutical and environmental samples without laborious sample preparation procedures. This is the first report to describe the use of BDD electrodes for NTZ monitoring and environmental sample analysis using an eco-friendly approach.

Research on carbon black and cerium co-doped Ti4O7-CB-Ce electrocatalytic oxidation of tetracycline-based antibiotics.

Elemental doping is a promising way for enhancing the electrocatalytic activity of metal oxides. Herein, we fabricate Ti/ Ti4O7-CB-Ce anode materials by the modification means of carbon black and cerium co-doped Ti4O7, and this shift effectively improves the interfacial charge transfer rate of Ti4O7 and •OH yield in the electrocatalytic process. Remarkably, the Ti4O7-CB-Ce anode exhibits excellent efficiency of minocycline (MNC) wastewater treatment (100% removal within 20 min), and the removal rate reduces from 100 to 98.5% after five cycles, which is comparable to BDD electrode. •OH and 1O2 are identified as the active species in the reaction. Meanwhile, it is discovered that Ti/ Ti4O7-CB-Ce anodes can effectively improve the biochemical properties of the non-biodegradable pharmaceutical wastewater (B/C values from 0.25 to 0.44) and significantly reduce the toxicity of the wastewater (luminescent bacteria inhibition rate from 100 to 26.6%). This work paves an effective strategy for designing superior metal oxides electrocatalysts.

Boosted Electrocatalytic Degradation of Levofloxacin by Chloride Ions: Performances Evaluation and Mechanism Insight with Different Anodes.

As chloride (Cl-) is a commonly found anion in natural water, it has a significant impact on electrocatalytic oxidation processes; yet, the mechanism of radical transformation on different types of anodes remains unexplored. Therefore, this study aims to investigate the influence of chlorine-containing environments on the electrocatalytic degradation performance of levofloxacin using BDD, Ti4O7, and Ru-Ti electrodes. The comparative analysis of the electrode performance demonstrated that the presence of Cl- improved the removal and mineralization efficiency of levofloxacin on all the electrodes. The enhancement was the most pronounced on the Ti4O7 electrode and the least significant on the Ru-Ti electrode. The evaluation experiments and EPR characterization revealed that the increased generation of hydroxyl radicals and active chlorine played a major role in the degradation process, particularly on the Ti4O7 anode. The electrochemical performance tests indicated that the concentration of Cl- affected the oxygen evolution potentials of the electrode and consequently influenced the formation of hydroxyl radicals. This study elucidates the mechanism of Cl- participation in the electrocatalytic degradation of chlorine-containing organic wastewater. Therefore, the highly chlorine-resistant electrocatalytic anode materials hold great potential for the promotion of the practical application of the electrocatalytic treatment of antibiotic wastewater.

Electrochemical oxidation of losartan on a BDD electrode: Influence of cathodes and electrolytes on the degradation kinetics and pathways

In this work, the influence of supporting electrolytes (sodium sulfate and sodium chloride) on the electrochemical oxidation of the antihypertensive drug losartan (LOS) was studied under different operating conditions such as current density (4.1–12.5 mA cm−2), electrolyte concentration (0.05–0.5 M), initial pollutant concentration (250–1000 μg L−1) and solution pH. The role of cathodes on the removal of LOS has been investigated using five different cathodes with carbonaceous cathodes showing better LOS removal. The effect of matrix composition has been studied using simulated water spiked with various constituents and real water matrices such as bottled water (BW) and wastewater (WW). The removal of LOS was pronounced while using a chloride electrolyte as compared to the sulfate electrolyte. The apparent rate constant increased on adding persulfate (PS) up to concentrations of 150 mg L−1 and decreased in the presence of bicarbonates and organic matter. The transformation products (TPs) formed during the electrochemical oxidation depended on the supporting electrolyte and two common TPs were identified in both electrolytes with a total of 4 TPs identified in the chloride medium and 7 TPs in the sulfate medium. Degradation pathways for LOS in both electrolytes have also been proposed.

Detection of Oxidants Such as Hydroxyl Radicals and Chlorine Electrogenerated on a BDD Electrode by Simple Methods

Detection of Oxidants Such as Hydroxyl Radicals and Chlorine Electrogenerated on a BDD Electrode by Simple Methods

Electrochemical oxidation of Rhodamine B in dye wastewater by a novel boron-doped diamond electrode: parameter optimization and degradation mechanism

The escalating pollution of water resources, predominantly attributable to the printing and dyeing industry, has garnered increased attention towards the treatment technology for such wastewater. In this study, an innovative boron-doped diamond electrode was employed for the removal of Rhodamine B (RhB) in dye wastewater through electrochemical oxidation (EO). The optimization of process parameters was achieved through a single-factor experiment. The degradation pathway of RhB was examined using Density functional theory calculations and Liquid chromatography-mass spectrometry. The results showed that when pH = 7, j = 40 mA∙cm−2, c(Na2SO4) = 0.035 mol·dm−3, and c0(RhB) = 50 mg·dm−3, the removal efficiency could reach 93.83% at 60 min. The EO process of RhB adhered to pseudo-first-order kinetics. The degradation process of RhB primarily encompasses several stages: deethylation reaction, destruction of the conjugated structure, decolorization, degradation reaction, and ring-opening mineralization reaction. This study offers a theoretical foundation for the practical implementation of BDD electrode electrochemical oxidation technology in dye wastewater treatment.

Oxidation of Trivalent Arsenic to Pentavalent Arsenic by Means of a BDD Electrode and Subsequent Precipitation as Scorodite

In order to deposit arsenic residues from copper production in a stable way, the trivalent arsenic must first be xidized to arsenic(V). A well-known but quite expensive method for this is oxidation with hydrogen peroxide. In order to enable the oxidation of arsenic on a large scale in the future, a potentially cheaper method has to be found, which offers the possibility of oxidizing extremely high arsenic concentrations. As a novel alternative, electrochemical oxidation using a boron-doped diamond electrode is investigated. Based on previous work, this paper concentrates on the presence of interfering ions during oxidation. Furthermore, it is shown that the electrochemically xidized arsenic(V) can be precipitated as scorodite. Finally, an economic analysis shows the potential financial benefit of oxidation via BDD electrodes compared to hydrogen peroxide.

Electrochemical Determination of Flavonoid Fisetin in Commercial Dietary Supplements Using a Boron‐Doped Diamond Electrode

AbstractFor the first time, a boron‐doped diamond electrode was utilized to quantitatively determine flavonoid fisetin (FST). Cyclic voltammetric studies have shown that the electrochemical oxidation of FST is irreversible and well‐separated two peaks (PA1 and PA2) in 0.1 M HNO3 solution. The effects of electrode pretreatment, solution pH, nature of the supporting electrolyte, and instrumental variables on the peak current and potentials of the FST were investigated by square‐wave voltammetry (SWV) and then optimum ones were determined. It was observed that the cathodically pre‐treated BDD (CPT‐BDD) electrode‘s performance was better than the other pre‐treatment procedures for increasing the FST oxidation signal. Under optimized conditions and using the SWV technique, the response of the first anodic peak (PA1) of the FST was proportional in a concentration range of 0.5–20.0 μg mL−1 (1.7×10−6–6.9×10−5 mol L−1) with a detection limit of 0.08 μg mL−1 (2.8×10−7 mol L−1). Also, it was successfully demonstrated that the proposed method is applicable in commercial nutritional supplement formulations.

Carbon Fiber Paper Sensor for Determination of Trimethoprim Antibiotic in Fish Samples.

The increase in anthropogenic pollution raises serious concerns regarding contamination of water bodies and aquatic species with potential implications on human health. Pharmaceutical compounds are a type of contaminants of emerging concern that are increasingly consumed and, thus, being frequently found in the aquatic environment. In this sense, an electrochemical sensor based on an unmodified and untreated carbon fiber paper (CPS-carbon paper sensor) was simply employed for the analysis of trimethoprim antibiotic in fish samples. First, the analytical conditions were thoroughly optimized in order for the CPS to achieve maximum performance in trimethoprim determination. Therefore, an electrolyte (0.1 M Britton-Robinson buffer) pH of 7 was selected and for square wave voltammetry parameters, optimum values of amplitude, frequency and step potential corresponded to 0.02 V, 50 Hz, and 0.015 V, respectively, whereas the deposition of analyte occurred at +0.7 V for 60 s. In these optimum conditions, the obtained liner range (0.05 to 2 µM), sensitivity (48.8 µA µM-1 cm-2), and LOD (0.065 µM) competes favorably with the commonly used GCE-based sensors or BDD electrodes that employ nanostructuration or are more expensive. The CPS was then applied for trimethoprim determination in fish samples after employing a solid phase extraction procedure based on QuEChERS salts, resulting in recoveries of 105.9 ± 1.8% by the standard addition method.

PCT degradation with electrooxidation (EOx) and ultrasound (US) hybrid process using different type electrodes: BDD, Ti/PbO2 and Ti/Pt

In this work, paracetamol (PCT) containing synthetic wastewater was investigated by electrooxidation (EOx) and ultrasound (US) hybrid process. Firstly, anode type (BDD, Ti/PbO2, and Ti/Pt) and process types including ultrasound (US), electro-oxidation (EOx) and hybrid process (EOx-US) were investigated for the degradation of paracetamol (PCT). The PCT degradation efficiency for US, EOx and EOx-US using BDD anode were obtained as < 1%, 70.5 % and 92.4 %, respectively. US-EOx process was found the most effective process in PCT and TOC degradation by using BDD electrodes because of the synergistic effect between sonolysis and electrocatalysis. Then, the effects of operation parameters such as US frequency (100–600 kHz) and US power (25–100 W), conductivity (3500–5500 μS cm−1), current density (50–500 A m−2), initial PCT concentration (20–500 ppm) and pH (2–8) on the PCT degradation with time dependency by EOx-US hybrid process were investigated. The optimum conditions were found as 200 kHz, 75 W, pH 2, 4500 μS cm−1, 100 A m−2, and 100 ppm when the PCT and TOC degradation efficiencies and the operating circumstances were considered. Additionally, the toxicity of the treated wastewater was examined, and it was discovered that the byproducts' formation caused the inhibition ratio to rise, making the solution more toxic than the initial solution. Frequency effect has not been studied much in hybrid processes in the literature, and it makes this study in this sense valuable.

From lab-scale to pilot-scale treatment of real wastewater from the production of rayon fiber

The subject of our study involved the treatment of real process wastewater from the production of rayon fiber. During the annual monitoring of the production facility, we performed a mass balance of three problematic sources of process wastewater and analyzed them repeatedly. All three sources showed high values of COD = 0.4–30 g/L, TOC = 0.09–7.1 g/L and the concentration of Zn2+ 0.09–0.5 g/L. At a total volume of 1.84 million m3, this represents a significant pollution source for the Elbe River. At lab-scale, we tested a combination of filtration, microfiltration, and oxidation using the Fenton, electro-assisted Fenton, and the electrochemical oxidation methods, both on the plate and newly developed macroporous BDD electrodes on a ceramic substrate, along with the final adsorption of Zn2+ emissions on the strongly acidic cation exchange resin Lewatit Mono plus S108. It was tested in Na+ and H+ cycles. Using an optimized technological sequence, we have achieved a COD reduction of up to 98%, and a TOC reduction of 85%. During the H+ cycle cation regeneration by sulfuric acid, Zn2+ emissions were converted to zinc sulfate that can be recycled in the spinning bath of the production process. The method was verified at a pilot scale.

Fabrication of the high efficient novel SiC foam based 3D metal oxide anodes with long life to improve electrocatalytic oxidation performance

The SiC foam is a promising electrode substrate material because of its huge specific surface area and low price. The novel three dimensions (3D)-PbO2 and 3D-SnO2-Sb anodes using SiC foam as a substrate were first prepared to reduce the energy consumption of wastewater electrochemical oxidation treatment. The results of the electrochemical degradation of alizarin red S (ARS) in a flow-through reactor depicted that the ARS and chemical oxygen demand (COD) degradation rate constants of 60 pores per inch (PPI)-SiC/SnO2-Sb anode are 8 and 1.82 times that of the costly BDD electrode. For 60 PPI-SiC/SnO2-Sb/PbO2 anode, it is 10.12 and 1.35 times higher. The 3D-SiC/SnO2-Sb anode has a 142–218 times longer lifetime than that of the flat-Ti/SnO2-Sb electrode. Its lifetime is also obviously longer than that of the SnO2 electrode with the addition of an intermediate layer or advanced materials modified in the reported literature. A new failure mechanism of the 3D-SiC-based electrodes is elaborated which is different from the Ti-based electrodes. An accurate fluid model is constructed based on the micro-CT and CFD simulation to study the enhancement mechanism of the flow field. The results show that the turbulent kinetic energy and vorticity of the reactor are 3–6 times higher than that with 2D electrodes. The residence time distribution shows that the flow field of the 3D electrode exhibits a more approximate plug flow with no dead zones. Due to their high performance and long life, 3D-SiC-based SnO2-Sb and PbO2 anodes have good prospects for commercial applications.

Electrochemical Oxidation of Anastrozole over a BDD Electrode: Role of Operating Parameters and Water Matrix

The electrochemical oxidation (EO) of the breast-cancer drug anastrozole (ANZ) is studied in this work. The role of various operating parameters, such as current density (6.25 and 12.5 mA cm−2), pH (3–10), ANZ concentration (0.5–2 mg L−1), nature of supporting electrolytes, water composition, and water matrix, have been evaluated. ANZ removal of 82.4% was achieved at 1 mg L−1 initial concentration after 90 min of reaction at 6.25 mA cm−2 and 0.1 M Na2SO4. The degradation follows pseudo-first-order kinetics with the apparent rate constant, kapp, equal to 0.022 min−1. The kapp increases with increasing current density and decreasing solution pH. The addition of chloride in the range 0–250 mg L−1 positively affects the removal of ANZ. However, chloride concentrations above 250 mg L−1 have a detrimental effect. The presence of bicarbonate or organic matter has a slightly negative but not significant effect on the process. The EO of ANZ is compared to its degradation by solar photo-Fenton, and a preliminary economic analysis is also performed.

Influence of anode material and chlorides in the new-gen solid polymer electrolyte cell for electrochemical oxidation – Optimization of Chloroxylenol degradation with response surface methodology

• Efficient removal of Chloroxylenol with BDD/SPE in low conductive solutions. • First application of Ti/RuO 2 (DSA) as anode coupled with solid polymer electrolyte. • Application of response surface methodology for process optimization. • Optimization allows decreasing the energy consumption preserving COD removal. • Promising results for DSA/SPE application in chlorinated environments. In this study the solid polymer electrolyte – based (SPE-based) system recently developed for electrochemical wastewater treatment is used for the degradation of Chloroxylenol (CXL). To the best of authors knowledge, this is the first study that deals the investigation of the effect of anode material in such electrochemical cell configuration. The most used BDD/SPE cell is compared with DSA/SPE (Ti/RuO 2 anode) system considering the effect of chlorides concentration to activate the process mediated by active chlorine. The preliminary tests to evaluate the feasibility of the process show that BDD/SPE is able to completely degrade the CXL reaching a COD removal close to 90 % also in absence of supporting electrolyte and in a low conductive solution (0.025 mS cm −1 ). The DSA anode suffers the lack of chlorides in solution but became more competitive when NaCl is added, with a maximum COD removal equal to 71.6 % with 50 mM NaCl. The response surface methodology based on three-factors Doehlert matrix is applied to optimize the operating conditions for both systems. The selected factors are the current density (2–20 mA cm −2 ), the NaCl concentration (0–20 mM), and CXL concentration (10–100 mg L −1 ). The optimization analysis allows identifying the operating conditions needed to maximize COD removal and to minimize energy consumptions for BDD/SPE and DSA/SPE setups. In particular, the RSM analysis shows that under peculiar conditions (i = 15.5 mA cm −2 ; NaCl > 13 mM) DSA/SPE can reach a COD removal analogous to those obtained with BDD electrode over 90%, suggesting the possibility to exploit this electrode material in solid polymer electrolyte electrochemical cells.

Electrochemical degradation of tetracycline hydrochloride in sulfate solutions on boron-doped diamond electrode: The accumulation and transformation of persulfate

In this study, a novel electrifying mode (divided power-on and power-off stage) was applied in the system of BDD activate sulfate to degrade tetracycline hydrochloride (TCH). The BDD electrode could activate sulfate and H2O to generate sulfate radicals (SO4•-) and hydroxyl radicals (•OH) to remove TCH, and SO4•- could dimerize to form S2O82−. Then, the S2O82− was activated by heat and quinones to generate SO4•- for the continuous degradation of TCH during the power-off stage. In addition, the intermittent time has a significant effect on the degradation of TCH. Factors, affecting the accumulation of S2O82−, were analyzed using a full factorial design, and the accumulation of S2O82− could reach 16.2 mM in 120 min. The results of electron spin resonance and radical quenching test showed that SO4•-, •OH, direct electron transfer (DET), and non-radical in the system could effectively degrade TCH, and SO4•- was dominated. The intermediate products of TCH were analyzed by HPLC-QTOF-MS/MS, and the TCH mainly underwent hydroxylation, demethylation and ring opening reactions to form small molecules, and finally mineralized. The results of the feasibility analysis revealed that some intermediates have high toxicity, but the system could improve the toxicity. The results of energy consumption indicated that the intermittent electrifying mode could make full use of the persulfate generated during the power-on stage and reduce about 30% energy consumption. In conclusion, this work demonstrated that it was economically feasible to degrade TCH in wastewater by activating sulfate with BDD electrodes with an intermittent electrifying mode.

E-peroxone process of a chlorinated compound: Oxidant species, degradation pathway and phytotoxicity

An electro-peroxone (EP) process was conducted in an up-flow bubble column reactor with BDD electrodes. The efficiency of the process was tested in the 4-Chlorophenol (4-CPh) mineralization and compared with that attained by single treatments like ozonation (O3) and electro-oxidation (EO). At [TOC]o= 56 mg·L−1, pHo= 7.0, T = 293 K, j = 0.06 A·cm−2, t = 120 min, the oxidation power decreased in the following order EP>EO>O3, and the TOC removed was, in the same order, 100%> 93%> 40%. The calculated synergy coefficient was 0.31, while the mineralization current efficiency percentage (MCE%) and the energy consumption (EC) were 12.24% and 11.48%, 2.84 and 2.31 kW·h−1, for EP and EO, respectively. The germination percentage of Lactuca sativa, was 100%, 30% and 20%, at the end of EP, EO and O3, respectively. This indicates that phytotoxicity, was only eliminated with EP. Based on the by-products, e.g. aromatic compounds (4-chlorocatechol, catechol, phenol, p-benzoquinone, hydroquinone) and carboxylic acids (maleic, formic, fumaric, succinic, oxalic, malonic and acetic acids) identified by UHPLC-UV/DAD and the changes of the concentration of chloride ion (Cl-), hypochlorite, chlorite, chlorate and perchlorate, a reaction pathway was proposed for the 4-CPh mineralization by the E-peroxone process. It was demonstrated that under the studied conditions both, hydrogen peroxide and ozone, are produced during EO. At the end of EO, H2O2, carboxylic acids and perhaps persulfates, are responsible for the phytotoxicity of the solution.

Periodic porous 3D boron-doped diamond electrode for enhanced perfluorooctanoic acid degradation

Using diamond anodes for electrochemical removal of recalcitrant perfluorooctanoic acid (PFOA) pollutants has become an important strategy in recent research. However, the electrolysis removal efficiency of PFOA is still plagued by low electrochemical active surface area (EASA) and mass transfer limitation of conventional flat-plate diamond anodes. Herein, the periodic porous boron-doped diamond (PP-BDD) anodes were successfully prepared by 3D printing combined with hot-filament chemical vapor deposition (HF-CVD) technologies. The prepared PP-BDD anode achieves a higher PFOA kinetics (kapp = 0.022 min−1, the normalized rate constant is 6.6 m s−1) compared with the conventional 2D-BDD anode (kapp = 0.006 min−1, the normalized rate constant is 1.8 m s−1) at the applied density of 20 mA cm−2. The calculated mass transfer coefficient km of PFOA towards PP-BDD (2.6 × 10−5 m s−1) is about 6.1 times higher than that of 2D-BDD (0.42 × 10−5 m s−1), and the electron paramagnetic resonance (EPR) measurement verifies that PP-BDD produces more •OH and SO4•− radicals during the electrolysis process versus 2D-BDD. The unique periodic pore structure enables PP-BDD higher EASA than 2D-BDD and increases the mass transfer efficiency. Consequently, the number of electrolyte and PFOA molecule accessible diamond anode surface is increased. This work provides valuable guidance for the deterministic design of periodic pore structure-based BDD electrodes for efficient electrochemical oxidation (EO) of refractory pollutants.

Trinuclear Nickel Catalyst for Water Oxidation: Intramolecular Proton-Coupled Electron Transfer Triggered Trimetallic Cooperative O–O Bond Formation

Trinuclear Nickel Catalyst for Water Oxidation: Intramolecular Proton-Coupled Electron Transfer Triggered Trimetallic Cooperative O–O Bond Formation