Boron-doped Diamond Research Articles

Boron-doped Diamond MOSFETs with Gradual Channel Doping Density

Boron-doped Diamond MOSFETs with Gradual Channel Doping Density

A chemical coating strategy for assembling a boron-doped diamond anode towards electrocatalytic degradation of late landfill leachate

A chemical coating strategy for assembling a boron-doped diamond anode towards electrocatalytic degradation of late landfill leachate

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.

Peroxodicarbonate - a renaissance of an electrochemically generated green oxidizer.

The direct anodic conversion of alkali carbonates in aqueous media provides access to peroxodicarbonate, which is a safe to use and green oxidizer. Although first reports date back around 150 years, its low concentrations and limited thermal stability have consigned this reagent to oblivion. Boron-doped diamond anodes, novel electrolyser concepts for heat dissipation, and the mixed cation trick allow record breaking peroxodicarbonate concentrations >900 mM. The electrochemical generation of peroxodicarbonate was already demonstrated on a pilot scale. The inherent safety is ensured by the limited stability of the peroxodicarbonate solution, which decomposes under ambient conditions to oxygen and facilitates subsequent downstream processing. This peroxide has, in particular at higher concentrations, an unusual reactivity and seems to be an ideal reagent when peroxo-equivalents in combination with alkaline base are required. The conversions with peroxodicarbonate include the Dakin reaction, epoxidation, oxidation of amines (aliphatic and aromatic) and sulfur compounds, deborolative hydroxylation reactions, and many more. Since the base equivalents also represent the makeup chemical for pulping plants, peroxodicarbonate is an ideal reagent for the selective degradation of lignin to vanillin. Moreover, peroxodicarbonate can be used as a halogen-free bleaching agent. The emerging electrogeneration and use of this green platform oxidizer are surveyed for the first time.

Correction: Vertically aligned boron-doped diamond nanostructures as highly efficient electrodes for electrochemical supercapacitors

Correction for ‘Vertically aligned boron-doped diamond nanostructures as highly efficient electrodes for electrochemical supercapacitors' by Shradha Suman et al., J. Mater. Chem. A, 2024, https://doi.org/10.1039/D3TA07728D.

Підготовка проб сечі для вольтамперометричного визначення лікарських речовин та оцінювання методики з погляду еколологічності

This work discusses the primary methods of preparing urine samples for voltammetric analysis. To serve as model analytes, well-known and commonly used medicinal substances were employed. These substances exhibit distinct pharmacological effects and undergo varying transformations at the electrodes under voltammetry conditions. The selected model analytes encompass two alkaloids of plant origin – quinine and platyphylline, the platyphylline metabolite – its N-oxide, and the synthetic antibacterial drug sulfadimethoxine. The determination of model analytes in prepared samples of urine was carried out using a boron-doped diamond electrode and a dropping mercury electrode. The action of ultrasound on the urine sample turned out to be the optimal method of sample preparation, which allows you to liquid or other types of extraction and significant dilution of sample urine. Furthermore, the environmental aspects of voltammetric analysis for medicinal substance determination in urine, exemplified by quinine, were assessed. Various approaches, such as AGREEprep, AGREE metrics, Green Certificate, and Blue Applicability Grade Index (BAGI), were employed to evaluate environmental considerations. All these assessments yielded high ratings, indicating compliance with the principles of green analytical chemistry for the voltammetric technique in quinine determination in urine.

Synthesis of gold nanoparticles with allicin to modify boron-doped diamond surface for oxygen sensor applications

Modification of surface of boron-doped diamond (BDD) film with gold nanoparticles (AuNPs) was carried out to increase its catalytic activity for an application as an oxygen sensor. Allicin was isolated from garlic by salting out extraction technique, and then used as the capping agent to synthesize AuNPs as it has a double bond structure that could be reacted to attach the BDD surface under UV light radiation. An average size of AuNPs at around 46,00 ± 9,06 nm was obtained, while the modification of the BDD surface by the synthesized AuNPs indicated that the surface of BDD could be covered by gold at around 0.6 % (w/w). Investigation of the AuNPs-modified BDD as a working electrode for the oxygen reduction by using cyclic voltammograms in 0.1 M phosphate buffer solution pH 7 observed a current peak at around -0.45 V (vs. Ag/AgCl). The current of this peak linearly increased proportionally to the dissolved oxygen concentrations (R2=0.9986). Moreover, a limit of detection of the dissolved oxygen of 0.12 ppm and limit of quantity 0.41 ppm could be achieved with excellent stability at 6.86% RSD with 6 repetitions and sensitivity at 19.086 μA/ppm indicated that the modified BDD is promising for applications as an oxygen sensor.

Core-shells particles grown in a tubular reactor: Influence of the seeds nature and MPCVD conditions on boron-doped diamond crystalline quality

A trend in the synthesis of Boron Doped Diamond (BDD) materials resides in increasing surface areas to exalt reactivity at the BDD/electrolyte interface. This can be achieved either by surface structuration of BDD films or conformal growth on 3D substrates. Another strategy considers isolated BDD particles, mainly obtained by milling of BDD layers that can be further deposited on surfaces or embedded in a conductive matrix. Here, we propose an alternative method to obtain boron-doped diamond particles using a core-shell approach, which consists in growing diamond coatings on spherical silica templates seeded with nanodiamonds. We investigated the effects of the nature and the density of diamond seeds as well as growth parameters on the crystalline quality of the coatings. The microstructure and the boron incorporation in the diamond shell was investigated by combining Scanning Electron Microscopy (SEM), UV Raman and X-ray Photoemission Spectroscopy (XPS) investigations. Such characterizations were compared to Scanning TEM (STEM) imaging, Energy Dispersive Spectroscopy (EDS) and Electron energy loss spectroscopy (EELS) performed on thin cross-sections of core-shells prepared by focused ion beam (FIB) milling.

Simultaneous estimation of total phenolic and alkaloid contents in the tea samples by utilizing the catechin and caffeine oxidation signals through the square-wave voltammetry technique

This work outlines the simultaneous estimation of the total phenolic and alkaloid contents in the tea samples by using catechin (C) and caffeine (CAF) oxidation signals at a non-modified boron-doped diamond (BDD) electrode. Two irreversible oxidation peaks, about + 1.03 (for C) and + 1.45 V (for CAF) vs Ag/AgCl in acetate buffer solution at pH 4.7, were seen in the cyclic voltammetric profile of the binary mixtures of C and CAF. In optimal conditions and utilizing the square-wave mode, the BDD electrode allows for simultaneous quantification of C and CAF within the concentration ranges of 5.0–100.0 µg mL−1 (1.72 × 10-5 − 3.45 × 10-3 mol/L) and 1.0–50.0 µg mL−1 (5.15 × 10-6 − 2.57 × 10-4 mol/L) respectively. The corresponding detection limits are 1.22 µg mL−1 (4.21 × 10-6 mol/L) for C and 0.11 µg mL−1 (5.66 × 10-7 mol/L) for CAF. Other phenolic compounds (like tannic acid, gallic acid, epicatechin, and epigallocatechin gallate) and other alkaloids (theophylline and theobromine) present in tea samples were examined for selectivity assessment. Ultimately, the applicability of the proposed approach was demonstrated by estimating the total phenolic and alkaloid contents in the black and green tea samples, expressed as C and CAF equivalents. The results obtained were contrasted against those acquired using UV–Vis spectrometry.

Platinum and Palladium Nanoparticles on Boron-Doped Diamond for the Electrochemical Detection of Hydrogen Peroxide: A Comparison Study

Neurodegenerative diseases such as Alzheimer’s and traumatic brain injury currently lacks a reliable diagnosis and treatment. This is, in part, due to knowledge gaps in the understanding of the mechanisms of brain injury. Hydrogen peroxide (H2O2) and other reactive oxygen and nitrogen species (ROS/RNS) are typical byproducts of oxygen metabolism and part of the inflammatory response cascades. Any disruptions in the uptake of ROS/RNS over an extended period of time can lead to oxidative stress, further adding to the neurodegeneration. While there are several modes of detection for ROS/RNS like H2O2, one of the major drawbacks is the lack of real-time detection. Electrochemical techniques offer real-time detection, are cheap, and easy to miniaturize. Carbon-based electrodes are particularly useful in electrochemical detection due to their ability to be adapted to different measurement systems. For neurochemical detection, carbon-fiber microelectrodes are most common but tend to foul with long-term exposure in a biological environment. Novel materials like boron-doped diamond (BDD) can mitigate this issue due to its general robustness and chemical inertness while also exhibiting small capacitive current, enhanced surface roughness, and a large potential window. As with other carbon-based electrodes, BDD can be modified to increase sensitivity towards a specific analyte like H2O2. In this work, we performed a comprehensive study of BDD electrodes modified with platinum (Pt) and palladium (Pd) nanoparticles for the detection of H2O2. The modification involves a 2-step wet chemical synthesis procedure directly onto the electrode surface. We look to expand the modification process not only to novel electrode materials, but also to metals that have not been used for this purpose previously. We optimized the modification process to find the parameters that yielded the best electrode for H2O2 detection. Several factors were investigated including the double-layer capacitance, electroactive surface area, electron transfer properties, and sensitivity to H2O2, among others. It was found that the modification yielded a 308x increase in sensitivity and a 36x decrease in limit of detection (LOD) and limit of quantification (LOQ) on Pd modified BDD when compared to bare BDD. A 256x increase in sensitivity and a 26x decrease in LOD and LOQ were observed on Pt modified BDD compared to the bare BDD. We found that the BDD modified with 1 mM Pd and electrodeposited to a 5 mC charge yielded an electrode with excellent sensitivity to H2O2 and provided a LOD and LOQ well within biological concentrations. The H2O2 measurements also exhibited excellent repeatability as the relative standard deviation (%RSD) was below 10% for all modifications. The future of this work will consist of two separate steps: 1) miniaturization of these modification methods to the microelectrode scale and 2) implementation of new materials in the modification process for H2O2 detections. In general, not only does this work further exemplify the versatility of diamond electrodes for the detection of biological H2O2, but the ease of this modification process makes the use of these electrodes fairly easy in any application where H2O2 is present.

Electrochemistry and Electronic Structure of the Deuterium-Grown Boron-Doped Diamond Interfaces

Integration of the first principles quantum mechanical simulations with electrochemistry represents a difficult research area due to the complexity and large size of real systems and computational limitations. On the one hand it is highly desirable to be able to predict electrochemical properties of materials and systems from simulations to limit the money expenditure for experimental work and accelerate applications [1]. On the other hand, utilization of ab-initio simulations to understand the experimentally observed phenomena is also required to embed them into a solid theoretical framework.To fulfill this task, several multiscale approaches are used with the density functional theory (DFT) being fundamental tool for investigation of electronic structure. DFT results can be further extended to build forcefields used in molecular dynamics (MD) [2] for larger scale simulations and non-equillibrium Green's functions for investigations of electronics and spintronics of nanodevices [3]. Semiconductor electrochemistry is one of the most important areas to explore this experiment-theory interface because of the necessity to develop new materials for photovoltaics, photoelectrochemistry, energy storage and conversion. The purpose of the following talk is to show the power of this paradigm by elucidation of the deuterium-grown boron doped diamond (BDD-D) material [4].A brief introduction to the material synthesis, chemical and physical properties is provided exploiting the synchrotron data of X-Ray absorption spectroscopy and X-Ray photoelectron spectroscopy. Then, a strong emphasis is put into merging the (photo)electrochemical data with the first principle results for better understanding of charge transfer phenomena in the nanoscale. Specifically, DFT calculations of projected local density of states clearly show the presence of highly occupied surface states on the (111) plane of BDD-D in contrast to its standard hydrogen-grown counterpart (BDD-H). The resulting surface states are capable of photocurrent generation in the visible light, which is strongly magnified in BDD-D. Moreover, photoelectrochemical measurements evidenced that photocurrents can be positive or negative depending on the bias - despite BDD being a p-type semiconductor. These confirm a profound role of surface states in the semiconductor electrochemistry and capability of photoinduced charge transfer in the modified materials. The proposed picture shines some new light on the commonly established paradigm of band bending as the key factor driving surface properties of the nanodiamond surfaces [5]. Figure. SEM images of a) BDD@D and b) BDD@H; c) grain size distribution among two samples; d) XRD patterns of the diamond films deposited in the D2/CH4 and H2/CH4 gas mixtures. Reflections at 2θ around 44°, 75°, and 91° correspond to the (111), (220), and (311) diamond lattice planes, respectively. Doubling of the reflections is related to the presence of Kα1 and Kα2 wavelengths in the X-ray radiation [4]. Acknowledgements: M.S., M.B., and M.F. thank Helmholtz-Zentrum Berlin (HZB) for the allocation of synchrotron radiation beamtime at HZB (Germany). M.S. gratefully acknowledges the financial support of these studies fromthe Gdansk University of Technology through the DEC-02/2021/IDUB/ II.1/AMERICIUM grant under the Americium – “Excellence Initiative – Research University” program. R.B. acknowledges the funding from the National Science Centre, Poland under the OPUS call in the Weave programme (Project number: 2021/43/I/ST7/03205).

Gas-Phase Electrochemical Conversion of Methane on Boron-Doped Diamond Gas Diffusion Anodes

Methane as the primary component of natural gas is used as fuel for energy supply and serves as a major feedstock for the chemical industry to produce hydrogen. In addition, renewable methane is becoming available via thermochemical, photo- or electrochemical, and biogenic routes. It remains a challenge, however, to efficiently activate the C-H bond of methane while keeping the reaction kinetics under control to form value added products (hydrocarbons or alcohols) and avoid complete oxidation to CO2 [1]. A promising way to selectively activate the C-H bond of methane is to utilize reactive oxygen species (ROS) [2]. ROS play a major role in the partial electrochemical oxidation of water to produce hydrogen peroxide with boron-doped diamond (BDD) anodes [3]. However, little is known about the role of ROS towards CH4 activation under electrochemical conditions. The goal of our work is to achieve control over product selectivity in the gas-phase electrochemical conversion of methane towards methanol or C2+ products [4, 5]. We also aim to explore the role of water in the methane conversion mechanism using in-situ electrochemical FT-IR spectroscopy.Experimentally, we use a BDD coated mesh as gas-diffusion anode electrode in a zero-gap gas-phase electrolyzer. The anode side of the cell is fed with humidified or dry CH4 (or He for control experiments) and humidified He or H2O are fed to the cathode side (to keep the Nafion 117 membrane humidified). The electro-oxidation of water is paired with hydrogen evolution.. The scheme of the membrane electrode assembly is shown on Fig. 1. A.In this talk, we discuss the effects of water content, gas flow rate and methane pressure on product selectivity. We observe the formation of CO2 and CO along with O2 when humidified CH4 is fed to the anode side of the electrolyzer (and H2O is fed to the cathode). CO2 and CO originate from the oxidation of CH4, as confirmed by control experiment with only He fed to the anode (Fig. 1. B). This suggests that ROS, generated at the BDD electrode by water partial oxidation, can oxidize methane. However, O2 is still the major product even in the presence of CH4 and both conversion and selectivity are low. The missing Faradaic efficiency (Fig. 1. C) can be related to non-detected CH4 oxidation products – for this, we are currently deploying additional analytical techniques besides gas-chromatography, e.g., IR, NMR, and HPLC, to detect minor products in both gas and liquid phases.When running experiments with humidified CH4 gas feed on the anode and humidified He gas feed on the cathode, we observe that the CO to CO2 ratio increases. This indicates that the selectivity changes significantly while the cell (and the membrane) dries out. Hence, we propose that the product selectivity can be controlled by tuning the humidity level.Finally, in experiments with dry CH4 gas fed to the anode and H2O recirculated to the cathode, we observe that both the increase of the CH4 gas flow rate (from 10 to 20 cm3 min-1) and pressure (atmospheric, +1 and +2 bar) lead to a consistent increase of the CO2 and CO formation yield. Hence, controlling CH4 gas flow rate and pressure provides further opportunity to control the conversion and selectivity.The results achieved so far motivate us to further investigate the joint effect of the above parameters by using a membrane capable to operate under dry conditions, in a system with improved H2O management.

Electroreduction of CO2 into CO Using Amine-Modified Diamond Electrode

Electroreduction of CO2 is promising to convert CO2 into value-added compounds since electroreduction does not necessarily require a catalyst because an electrochemical energy itself can activate the reactivity of CO2. Most of the reported studies on CO2 electroreduction use a metal electrode material, and the selectivity of reduction products depends on the metal species. However, as the use of noble or toxic metals should be avoided from the viewpoint of sustainability, a metal-free carbon-based material are desirable. Along these lines, we have focused on boron-doped diamond (BDD) as a carbon-based electrode in CO2 electroreduction. On the other hand, molecular modification of electrode surface is an important technique in various fields. Functional molecules can be covalently immobilized onto carbon electrodes by an electrografting method. Along these lines, we decided to immobilize amine on BDD surface, which integrates CO2 capture and storage technologies and CO2 electroreduction. Here, we prepared amine-modified BDD (NH2-BDD) to elucidate an effect of amine modification on CO2 electroreduction.Prior to the electrolysis experiments, linear sweep voltammetry (LSV) was performed to investigate the electrochemical difference between bare- and NH2-BDD. As an energetically equivalent criterion for the CO2 electroreduction, E red was defined as the potential at which the current density reached -30 µA/cm2; E red (vs. Ag/AgCl) were determined to be -1.56 and -1.16 V for bare-BDD and NH2-BDD, respectively. A positive shift of E red in the NH2-BDD electrode is probably because CO2 molecules form the C-N bond with the amino group on the electrode surface, which results in enhancing the electrophilicity of the carbon atom. Next, we investigated how amine modification affects the product selectivity in CO2 electroreduction. Products were CO, HCOOH, and H2 regardless of the type of electrode and applied potentials. Difference between the Faraday efficiencies (FE) of HCOOH and CO production was dependent on applied potentials in NH2-BDD. Particularly, in the most prominent case, the selectivity of CO production was 8 times higher for NH2-BDD than the case of bare-BDD. Since CO production requires the adsorption of intermediate species, CO2 • -, on the electrode surface, the adsorption of CO2 and CO2 • - would be promoted on NH2-BDD through the formation of C-N bond. In order to obtain the direct evidence for CO2 capturing by NH2-BDD during the electroreduction, in situ ATR-IR measurements were performed. We focused on the C=O (carbonyl) stretching vibration of the carbamate anion, observed in the region of 1700-1500 cm-1. In NH2-BDD, a broad peak attributed to the C=O stretching vibration was observed at around 1640 cm-1, and the peak intensity decreased as the applied potential became negative. This result strongly supports that CO2 was captured by amine at the BDD surface to form the carbamate anion and reduced to CO.The above discussion can be explained by the behavior of LSV of NH2-BDD, in which two drops were observed. The first drop at around -1.20 V (vs. Ag/AgCl) is probably ascribed to the reduction of CO2 captured by amine, and the second drop at around -1.70 V (vs. Ag/AgCl) is ascribed to the reduction of free CO2. Therefore, CO production would be favored at potentials between -1.20 and -1.70 V (vs. Ag/AgCl) and HCOOH production would be favored at potentials more negative than -1.70 V (vs. Ag/AgCl). These threshold potentials are in good agreement with the potentials at which the product selectivity switched. It is noted that, in bare-BDD electrodes showing the different E red, the selectivity of CO production was almost unchanged, which suggests that the potential dependence of product selectivity in CO2 electroreduction cannot be explained only by differences in E red. Therefore, the product selectivity was driven by the interaction between the surface amine groups and CO2, i.e. the reaction via carbamate formation. Figure 1

Low-Cost and Scalable Electrodes for Anodic Production of Hydrogen Peroxide Via 2e- Water Oxidation

Hydrogen peroxide (H2O2) is a crucial chemical that is widely utilized in various industrial processes. The conventional anthraquinone process for H2O2 production has limitations in terms of energy consumption, high costs, and waste generation [1]. An alternative, greener and more sustainable approach is the electrochemical production of H2O2 from oxygen and water using renewable energy. Our research group has been extensively investigating the two electron (2e-) water oxidation reaction (WOR) for production of H2O2 using various electrode materials, including metal oxides, commercial carbon materials, and boron-doped diamond (BDD) [2, 3]. We also investigated the role of carbonate ions (HCO3 - and CO3 2-) in the process of water oxidation to H2O2. The enhancing effect e of CO3 2- ions on anodic H2O2 production was studied in a continuous flow reactor, where the optimal flow rate, process configuration and cell design, and chemical stabilizer were determined. Among other parameters, chemical composition and pH regime of the electrolyte were found to be crucial.Recently, we explored the use of graphite bipolar plates (BPP) as a low-cost alternative to BDD electrodes for anodic H2O2 generation [4]. Three different commercial BPPs with varying fluoropolymer content were examined, and a correlation was found between fluoropolymer content and H2O2 generation. In that study we found that a BPP sample with high fluoropolymer content resulted in a stable H2O2 production for up to 100 hours at a current density of 200 mA cm–2, with a constant faradaic efficiency of 40%. The results demonstrate that low-cost commercial carbon electrode materials can selectively oxidize water to H2O2, enabling economically viable technical applications of anodic H2O2 production.

Anode Reaction Control for a Single-Compartment Electrochemical CO2 Reduction Reactor with a Surface-Activated Diamond Cathode.

The electrochemical reaction of carbon dioxide (CO2 ) in aqueous electrolyte solutions is attracting increasing attention for sustainable chemical production. Boron-doped diamond (BDD) electrodes have been previously shown to be very effective for the stable electrochemical production of formic acid from CO2 . Typically, the electrochemical production of formic acid by CO2 reduction (CO2 R) reaction is performed with a dual-compartment flow reactor equipped with a membrane separator. The problems caused by the membrane separator, such as scaling-up, complicated operational control and materials costs can be solved using a membrane free single-compartment reactor. Here we demonstrate anode reaction control for a single-compartment CO2 R flow reactor using a surface-activated BDD cathode and achieve a Faradaic efficiency for formic acid production of over 70 %.

Fast sequential determination of amoxicillin and clavulanate in pharmaceutical samples using batch injection analysis with amperometric detection

AbstractThe combination of amoxicillin (AMX) and clavulanic acid (CLA) is one of the most widely used antibiotic medicines in the world. This paper describes a novel electrochemical method for the fast sequential determination of AMX and CLA using batch injection analysis with amperometric detection (BIA‐AD) and boron‐doped diamond (BDD) as the working electrode. In the proposed strategy, AMX was selectively detected at +1.3 V and both compounds (AMX+CLA) at +1.8 V. The oxidation current from CLA was accessed by subtracting the currents detected at both potential pulses (i+1.8 V–i+1.3V) and using a simple correction factor. The developed method proved to be simple, cost‐effective, precise (RSD<1.3 %, n=10), rapid (>200 injection h−1), required simple sample preparation steps (dissolution and dilution only) and can be used in laboratories with minimal infrastructure (portable characteristics). The limits of detection were 0.31 (0.13) and 1.99 (0.47) μmol L−1 (mg L−1) for AMX and CLA, respectively. The results obtained by the proposed BIA‐AD method were comparable to those obtained by capillary electrophorese (95 % confidence level).

Sensitive and Selective Electrochemical Sensor for Antimony Using Boron-doped Diamond Nanoparticles

Sensitive and Selective Electrochemical Sensor for Antimony Using Boron-doped Diamond Nanoparticles

Carbon and nitrogen product distribution in the electrochemical degradation of nitrogen-heterocyclic compounds

We report for the first time the carbon and nitrogen product distribution during the electrochemical oxidation (EO) of pyrazine and related N-heterocyclic compounds (NHCs) present in the hard-to-treat wastewater from a biofuel production process. The experimental study was carried out using a boron-doped diamond anode. Identified and quantified intermediate products included oxamic acid, formamide, oxalic acid, and formic acid. Analysis of the C and N yields as a function of the extent of carbon removal reveals the influence of the current- and mass transfer-control operating regimes on product distribution. Carbon monoxide, which was detected among the gaseous products, suggests a possible decarbonylation pathway in the current-controlled regime. An apparent nitrogen gas and ammonium yields correlated linearly with the carbon removal, while nitrate yields significantly increased in the mass transfer-controlled regime. Nitrate and apparent nitrogen gas appear to form directly from organic nitrogen intermediates, rather than from the ammonium that also forms in the process. The research gives new insights into the NHCs degradation pathways, product distribution, and final water composition as a function of operating regime in the EO of recalcitrant wastewater.

Parametric Mathematical Model of the Electrochemical Degradation of 2-Chlorophenol in a Flow-by Reactor under Batch Recirculation Mode

2-Chlorophenol (2-CP) is a dangerous organic contaminant found in wastewater. In this work, 2.5 L of a 2-CP solution (1 mol/m3) was electrochemically treated in a flow-by reactor equipped with two boron-doped diamond electrodes (BDD) under batch recirculation mode for a period for 4 h, a current density of 0.14 A/cm2, a volumetric flow rate of 1 L/min, and pH = 7.3. In this work, a parametric mathematical model of the degradation efficiency of 2-CP was developed using an axial dispersion model and a continuous stirred tank for the flow-by reactor (FBR), which was constructed using a shell mass balance considering the dispersion and convection terms and the reservoir tank (CST), which was constructed using a mass balance of 2-CP. The parametric mathematic model of the electrochemical degradation of 2-chlorophenol was numerically resolved by employing the software package COMSOL Multiphysics® V. 5.3, where a mass transfer equation for diluted species and a global differential equation represents the FBR and CST, respectively. The results indicate that the parametric mathematical model proposed in this research fits the experimental results, and this is supported by the index performance values such as the determination coefficient (R2 = 0.9831), the mean square error (MSE = 0.0307), and the reduced root-mean-square error (RMSE = 0.1754). Moreover, the degradation efficiency of 2-CP estimated by the proposed model achieves 99.06%, whereas the experimental degradation efficiency reached 99.99%, a comparative error of 0.93%. This corroborates the predictive ability of the developed mathematical model and the effectiveness of the employed electrooxidation process. Finally, a 0.143 USD/L total operating cost for the electrochemical plant was estimated.

Synergistic roles of oxidation and self-aggregation in efficient ultrafiltration membrane fouling alleviation using a flow-through Sb-SnO2 anode during wastewater reclamation

The application of ultrafiltration (UF) in wastewater reclamation alleviates the demand for limited water supplies. However, the membrane fouling caused by the effluent organic matter (EfOM) becomes a major obstacle for UF application. In this study, a pre-oxidation strategy for UF using a Sb-SnO2 (ATO) anode in flow-through mode was proposed with the hopes to improve the performance of UF during wastewater reclamation. The results indicated that this flow-through ATO (FA) anode significantly outperformed a boron-doped diamond (BDD) anode in terms of EfOM degradation and membrane fouling control. It is noteworthy that apart from oxidation, the self-aggregation behavior of foulants was also involved in the mechanisms of membrane fouling mitigation. On the one hand, FA pre-oxidation relieved the burden of membrane fouling by decomposing the macromolecular EfOM into small molecular organic matter, and even mineralizing it. The effective destruction of unsaturated EfOM by FA pre-oxidation made a remarkable contribution to fouling mitigation due to the strong correlation between the total fouling index and UV254. On the other hand, the surface morphology of membrane and interface properties of foulants revealed the self-aggregation behavior of foulants. FA pre-oxidation made the foulants aggregate spontaneously and reduced the potential of forming a dense cake layer on the membrane surface, which was conductive for water permeation. Overall, FA pre-oxidation proved to be a feasible and chemical-free option for UF pretreatment to simultaneously produce high-quality reused water and alleviate membrane fouling during wastewater reclamation.