Electrochemical Technologies for Detecting and Degrading Benzoquinone Using Diamond Films

Electrochemical oxidation of surfactants as an essential step to enable greywater reuse

The practical application of electrochemical oxidation technology for the removal of surfactants from greywater was evaluated using sodium dodecyl sulfate (SDS) as a model surfactant. Careful selection of electrocatalysts and optimization of operational parameters demonstrated effective SDS removal in treating a complex greywater matrix with energy consumption below 1 kWh g-1 COD (Chemical Oxygen Demand), paving the way for a more sustainable approach to achieving surfactant removal in greywater treatment when aiming for decentralized water reuse. Chromatographic techniques identified carboxylic acids as key byproducts prior to complete mineralization. These innovative approaches represent a novel pathway for harnessing electrochemical technologies within decentralized compact devices, offering a promising avenue for further advancements in this field.

Towards the design of mechanical flexible electrodes for sensing: Self-standing polypyrrole-copper nanocomposites

Self-standing electrodes with intrinsic conductivity and high electrocatalytic activity emerge as an alternative to existing sensors given their promising flexibility and wearability. Herein we demonstrate the fabrication of flexible sensors based on a hybrid nanocomposite of self-supported polypyrrole electrodes modified with copper nanoparticles (PPy-Cu) for the electrochemical detection of dopamine. The surface morphology and composition of flexible nanocomposite electrodes was studied using scanning electron microscopy (SEM), in combination with elemental mapping through energy dispersive X-ray spectroscopy (EDS). Surface characterization by X-ray photoelectron spectroscopy (XPS) revealed that copper exists in both Cu(0) and Cu(II) forms. The incorporation of copper nanoparticles in the self-standing polypyrrole matrix introduced additional electroactive sites, further enhancing charge transfer, and improving the device's sensitivity. The sensing capability of self-standing PPy-Cu electrodes was evaluated using chronoamperometric measurements and optimized at various copper electrodeposition times. PPy-Cu 120s showed great performance for dopamine sensing with a low limit of detection of 1.19 μM and a linear range of 2.5 μM-250 μM. Additionally, the self-standing sensor is comprised entirely of Polypyrrole, a biocompatible polymer, and Copper nanoparticles, making it sustainable and environmentally friendly. These encouraging results pave the way for the development of next-generation flexible sensors for the detection of neurotransmitters and environmentally relevant analytes.

Electrochemical oxidation and sensing of para benzoquinone using a novel SPE based disposable sensor

Para-benzoquinone (PBQ) is an emerging micro-contaminant owing to its chronic toxicity to plants and animals as well as its potential to induce cytotoxicity in primary rat hepatocytes and kidney cell injury. Hence, it is of utmost importance to monitor this contaminant in industrial wastewater and groundwater. In this article, we devised a unique disposable sensor that is based on a screen-printed electrode using MnO2@Co-Ni MOFs/fMWCNTs nanocomposite and is able to detect PBQ. The as-produced nanocomposite was prepared via ultrasonic assisted reflux condition and thoroughly examined by several physicochemical characterisation methods such as SEM, EDX, TEM, Raman, AFM, UV-visible, and FT-IR. Moreover, electrochemical methods like CV, DPV, EIS, and chronoamperometry were used for detecting PBQ on MnO2@Co-Ni MOFs/fMWCNTs/SPCE. Sensor performance has been investigated thoroughly and optimized to enhance the analytical potential of the fabricated sensor. DPV analysis was done on MnO2@Co-Ni MOFs/fMWCNTs that exhibit high selectivity, low peak potential, a broader linear detection range (0.005 mM-30 mM), and a LOD of 0.0027 ± 0.0005 mM. The designed electrode has shown remarkable reproducibility and excellent repeatability, with relative standard deviations of 0.12%, and 0.17%, respectively. Additionally, MnO2@Co-Ni MOFs/fMWCNTs/SPCE have been used to analyse PBQ in industrial wastewater samples, and the results have shown a significant level of recovery between 96.91 and 105.67%. Moreover, the PBQ sensor displays high applicability and was verified via the use of HPLC techniques. This disposable sensor is quick, easy, and cost-effective, so it can be useful in the future for analysing other phenolic contaminants present in environmental samples.

Electrochemical degradation of ciprofloxacin through a DoE-driven optimization in a filter-press type reactor under batch recirculation mode

In this work, the electrochemical degradation of ciprofloxacin (CIP) was studied in a filter-press-type reactor without division in a batch recirculation manner. For this purpose, two boron-doped diamond (BDD) electrodes (as cathode and anode) were employed. Also, the optimal operating conditions were found by response surface methodology (RSM) following a central composite face-centered design with three factors, namely current intensity (i), initial pH (pH0), and initial concentration ([C]0) with two responses, namely remotion efficiency (η) and operating cost. Optimal operating conditions were i = 3 A, pH0 = 8.49, and [C]0 = 33.26 mg L-1 within an electrolysis time of 5 h, leading to a maximum removal efficiency of 93.49% with a minimum operating cost of $0.013 USD L-1. Also, a TOC analysis shows an 80% of mineralization extent with an energy consumption of 5.11 kWh g-1 TOC. Furthermore, the CIP degradation progress was followed by mass spectrometry (LC/MS) and a degradation pathway is proposed.

Hybrid electrolysis and membranes system for apple packing houses water treatment

The apple industry uses high flows of potable quality water to transport and clean the apple, which is regularly contaminated. Thus, it is necessary to implement an efficient water treatment system during the industrial process, providing reductions in the intake and release flows. A hybrid system was developed by applying the electrolytic treatment by electrocoagulation using a batch process (Step 1) and a continuous process (Step 2), followed by a microfiltration membrane separation (MSP) process (Step 3). The optimal conditions for removal of organic matter, chemical oxygen demand, total suspended solids (TSS), turbidity, color, and fungi obtained in Step 1 were a hydraulic detention time of 40 min, stirring at 40 rpm, current density of 20 A/m2, pH of 8.00, and temperature of 10 °C. These findings led to a successful implementation in Step 2, which evolved into Step 3, where tests in the combined continuous electrolytic reactor together with MSP showed significant removal rates, notably reaching up to 54% organic matter (OM) removal, 72% chemical oxygen demand (COD) removal, 83% TSS removal, 92% haze and color removal, and 100% mildew removal. The hybrid system proved to be a promising alternative for implementation in the processing industry, minimizing environmental impacts and costs.

Evaluating the catalytic effect of Fe@Fe2O3-modified granulated cork as an innovative heterogeneous catalyst in electro-Fenton degradation of benzoquinone in different aqueous matrices

This study investigated the potential of a novel biomass-derived cork as a suitable catalyst after its modification with Fe@Fe₂O₃ for in-situ application in heterogeneous electro-Fenton (HEF) process for benzoquinone (BQ) elimination from water. No attempts on the application of modified granulated cork (GC) as a suspended heterogeneous catalyst in the HEF process for water treatment have been published yet. GC was modified by sonification approach in a FeCl₃ + NaBH₄ solution to reduce the ferric ions to metallic iron in order to obtain Fe@Fe₂O₃-modified GC (Fe@Fe₂O₃/GC). Results clearly demonstrated that this catalyst exhibited excellent electrocatalytic properties, such as a high conductivity as well as relatively high redox current and possessed several active sites for water depollution applications. Using Fe@Fe₂O₃/GC as catalyst in HEF, 100% of BQ removal was achieved in synthetic solutions by applying 33.3 mA cm^-2 after 120 min. Different experimental conditions were tested to determine that best possible conditions can be as follow: 50 mmol L^-1 Na₂SO₄ and 10 mg L^-1 of Fe@Fe₂O₃/GC catalyst using Pt/carbon-PTFE air diffusion cell by applying 33.3 mA cm^-2. Nevertheless, when Fe@Fe₂O₃/GC was used in the HEF approach to depollute real water matrices, no complete BQ concentration was removal achieved after 300 min of treatment, achieving between 80 and 95% of effectiveness.

A fluorescent covalent organic framework for visual detection of p-benzoquinone

P-benzoquinone (PBQ) is toxic and harmful for health. The development of portable sensor to realize the detection of PBQ is of great significance. Herein, a novel covalent organic framework (COF_ML-TFPB) with intramolecular charge transfer and aggregation induced emission properties was proposed via condensation reaction of melem (ML) and 1,3,5-tris (4-formylphenyl) benzene (TFPB). COF_ML-TFPB shows strong fluorescence in both solution and solid state and can be used for the fluorescence detection of PBQ. Due to the internal filtration effect and photoinduced electron transfer effect, PBQ can quench the fluorescence of COF_ML-TFPB. The developed COF_ML-TFPB fluorescent sensor displayed a wide linear range for PBQ from 0.138 ng mL^-1 - 35 μg mL^-1, and the detection limit was 0.046 ng mL^-1. In addition, fluorescent test paper for rapid and portable detection of PBQ was also developed by depositing COF_ML-TFPB on filter paper directly. It reduces the cost and time of detection and realizes the semiquantitative detection of PBQ. Moreover, the fluorescence color was converted into digital RGB value to calculate the concentration of PBQ accurately by a smartphone. This method realizes the portable qualitative and semiquantitative determination of PBQ.

Tetracycline removal from aqueous solution by electrooxidation using ruthenium-coated graphite anode

This paper reports the electrochemical oxidation treatment of 80 mL of acidic aqueous solutions with 0.2 mM of the drug tetracycline in 25 mM Na₂SO₄ using a lab-scale electrochemical cell. The performance of tetracycline removal with Ru-coated graphite by the chemical bath deposition (CBD) and raw graphite anode has been demonstrated. The effects of operating parameters were tested such as pH, applied current, supporting electrolyte concentration, and initial tetracycline concentration. The best tetracycline degradation was obtained with Ru-coated graphite anode due to its higher oxidation power, which allowed the complete degradation of refractory compounds. The modified surface structure of the Ru-coated graphite anode was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray (EDX). The EO process with Ru-coated graphite anode allowed 93.8% tetracycline abatement after 100 min of electrolysis at an applied current of 100 mA. In all cases, tetracycline decay obeyed pseudo-first-order kinetics. The tetracycline removal performance of graphite electrodes with nano coating on graphite has offered a performing alternative. A Comparative study revealed that electrolysis with Ru-coated graphite acted as a better electrode material than raw graphite for the catalytic reaction.

An efficient Fe2+ assisted UV/electrogenerated-chlorine process for carbamazepine degradation: The role of Fe(IV)

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe²⁺ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe²⁺) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe²⁺ (AO-Cl/Fe²⁺) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe²⁺ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m³-log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of ^•OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO₂) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe²⁺ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., ^•OH and Cl^•) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation.

Highly porous seeding-free boron-doped ultrananocrystalline diamond used as high-performance anode for electrochemical removal of carbaryl from water

Boron-doped diamond (BDD) electrodes are regarded as the most promising catalytic materials that are highly efficient and suitable for application in advanced electrochemical oxidation processes targeted at the removal of recalcitrant contaminants in different water matrices. Improving the synthesis of these electrodes through the enhancement of their morphology, structure and stability has become the goal of the material scientists. The present work reports the use of an ultranano-diamond electrode with a highly porous structure (B-UNCD_WS/TDNT/Ti) for the treatment of water containing carbaryl. The application of the proposed electrode at current density of 75 mA cm^-2 led to the complete removal of the pollutant (carbaryl) from the synthetic medium in 30 min of electrolysis with an electric energy per order of 4.01 kWh m^-3 order^-1. The results obtained from the time-course analysis of the carboxylic acids and nitrogen-based ions present in the solution showed that the concentrations of nitrogen-based ions were within the established maximum levels for human consumption. Under optimal operating conditions, the proposed electrode was successfully employed for the complete removal of carbaryl in real water. Thus, the findings of this study show that the unique, easy-to-prepare BDD-based electrode proposed in this study is a highly efficient tool which has excellent application potential for the removal of recalcitrant pollutants in water.

Electrochemical oxidation of ciprofloxacin in different aqueous matrices using synthesized boron-doped micro and nano-diamond anodes

The present work investigates the electrocatalytic performance of two different morphologies of boron doped-diamond film electrode (microcrystalline diamond - MCD, and nanocrystalline diamond - NCD) used in electrochemical oxidation for the removal of the antibiotic ciprofloxacin (CIP). A thorough study was conducted regarding the formation of the MCD and NCD films through the adjustment of methane in CH₄/H₂ gas mixture, and the two films were compared in terms of crystalline structure, apparent doping level, and electrochemical properties. The physicochemical results showed that the NCD film had higher sp² carbon content and greater doping level; this contributed to improvements in its surface roughness, as well as its specific capacitance and charge transfer, which consequently enhanced its electrocatalytic activity in comparison with the MCD. The results obtained from CIP removal and mineralization assays performed in sulfate medium also showed that the NCD was more efficient than the MCD under all the current densities investigated. The effects of CIP concentration and the evolution of the final by-products, including short-chain carboxylic acids and inorganic ions, were also investigated. The electrochemical performance of the NCD was evaluated in different aqueous matrices, including chloride medium, real wastewater and simulated urine. The application of the NCD led to complete or almost complete CIP degradation, regardless of the medium employed. The kinetic constant rates obtained under the different media investigated were as follows: synthetic urine (0.0416 min^-1 - R² = 0.991) < real wastewater (0.0923 min^-1 R² = 0.997) < synthetic matrix containing chloride (0.1992 min^-1 - R² = 0.995); this shows that the pollutant degradation was affected by the type of aqueous matrix and the oxidants that were electrogenerated in situ. The results obtained from the analysis of electrical energy per order (EE/O) showed that the treatment of simulated urine spkiked with required the highest energy consumption, followed by the real effluent and synthetic matrix containing chloride. The present study proves the viability of electrocatalytic nanostructured materials to the treatment of antibiotics in complex matrices.

Application of boron-doped diamond, Ti/IrO2, and Ti/Pt anodes for the electrochemical oxidation of landfill leachate biologically pretreated by moving bed biofilm reactor

Conventional biological treatments used in most Indonesian landfill sites are mostly ineffective in treating stabilized landfill leachates to meet the standard regulation. Thus, a combination of biological and electrochemical process is offered to successfully treat leachates containing a high concentration of organic and nitrogenous compounds. In this study, a moving bed biofilm reactor (MBBR) was applied prior to electrochemical oxidation by using boron-doped diamond (BDD), Ti/IrO₂, and Ti/Pt anodes with applied current of 350, 400 and 450 mA. The objectives were to investigate the effect of anode type and the applied current on the removal of organics as well as total nitrogen from the MBBR-treated leachate with electrochemical oxidation. The optimum removal of chemical oxygen demand (COD) observed on the Ti/Pt anode was 78% by applying 400 mA, with an estimated energy of 56.7 Wh g L^-1. In the case of Ti/IrO₂ and BDD anodes, the optimum removal of COD was 76 and 85% with an energy consumption of 58.9 and 36.9 Wh g L^-1, respectively, both achieved at 350 mA. Although all anodes showed less-satisfactory performances for total nitrogen reduction, around 46-95% removal of nitrogenous compounds was achieved by MBBR, with their partial conversion to nitrates.

A novel gradient current density output mode for effective electrochemical oxidative degradation of dye wastewater by boron-doped diamond (BDD) anode

In order to solve the problems of high energy consumption and low current efficiency in electrochemical oxidation (EO) degradation under the traditional constant output process (COP), a gradient output process (GOP) of current density is proposed in this paper. That is, the current density is gradually reduced in a fixed degradation time, and the Reactive Blue 19 simulated dye wastewater was used as the degradation target. The general applicability of the process was further confirmed by studying the optimal gradient current density output parameters, the dye concentration, electrolyte concentration and other dye compounds with different molecular structures. The corresponding results show that the chemical oxygen demand (COD) removal (78%) and the color removal (100%) under the GOP are similar to those in the COP, and the overall energy consumption is reduced by about 50% compared with that in the traditional constant current mode. Moreover, the current efficiency in the middle and late stages of EO process has increased by 8.6 times compared with COP.