Use Of Electrochemical Oxidation Research Articles

Degradation of carbendazim in aqueous solution by different settings of photochemical and electrochemical oxidation processes

The present study analyzed the performance of photochemical and electrochemical techniques in the degradation and mineralization of the pesticide carbendazim (CBZ). Direct photolysis (DP), heterogeneous photocatalysis (HP), photoelectrocatalysis (PEC), and electrochemical oxidation (EO) were tested, and the influence of UV radiation, current density (j), and supporting electrolyte concentration were evaluated. The results suggest that CBZ is only degraded by DP when UV-C254nm is used. For HP, the CBZ degradation was observed both when UV-A365nm or UV-C254nm were used, which is related to the reactive oxygen species (ROS) formed by the photocatalytic activity (photon-ROS). Neither DP nor HP were able to mineralize CBZ, demonstrating its resistance to photomediated processes. For EO, regardless of the j, there were higher CBZ degradation and mineralization than those observed when using DP and HP. The increase in the supporting electrolyte concentration (Na2SO4) did not affect the levels of degradation and mineralization of CBZ. Concerning the PEC, a CBZ mineralization of 52.2% was accomplished. These findings demonstrate that the EO is the main pathway for CBZ mineralization, suggesting an additional effect of the electro-ROS on the photon-ROS and UV-C254nm. The values of mineralization, kinetics, and half-life show that PEC UV-C254nm with a j of 15 mA cm−2 was the best setting for the degradation and mineralization of CBZ. However, when the values of specific energy consumption were considered for industrial applications, the use of EO with a j of 3 mA cm−2 and 4 g L−1 of Na2SO2 becomes more attractive. The assessment of by-products formed after this best cost-efficient treatment setting revealed the presence of aromatic and aliphatic compounds from CBZ degradation. Acute phytotoxicity results showed that the presence of sodium sulfate can be a representative factor regarding the toxicity of samples treated in electrochemical systems.

Decontamination of real urban sewage-comparison between Fenton and electrochemical oxidation.

Advanced oxidation processes have been used for wastewater treatment due to their capacity to reduce the organic loading and for their fast reactions. In this paper, we explore the viability of isolated and sequential use of electrochemical oxidation and Fenton processes into treatment of real raw urban sewage. The electrochemical process was carried out using DSA®-Cl2 electrodes and factorial planning in order to investigate the influence of pH, current density, and electrolyte. Fenton reaction was also used and H2O2 and Fe2+ concentration effects were investigated. The efficiency was estimated by chemical oxygen demand (COD) removal and in the optimized conditions the effluent was characterized by turbidity, suspended/dissolved/total solids, ammonia, chloride ions, free chlorine, nitrite, and potassium analysis and bioassays with Artemia ssp. and Lactuca sativa. The study demonstrated that the use of electrochemical technique followed by Fenton allowed an improvement in the degradation of organic matter and reduction of turbidity and solid content, reaching reductions of 86.8, 96.4, 99.4, 56.1, and 66.7% for COD, turbidity, SS, DS, and TS, respectively. The associated treatment also contributed to the reduction of energy consumption by 74.9%, from the 23.9 kWh m-3 observed during the electrochemical treatment isolated to the 6 kWh m-3 during the associated process. All the treatments presented toxicity reduction, with the electrochemical process achieving the best results.

Degradation of dexamethasone in water using BDD anodic oxidation and persulfate: reaction kinetics and pathways

AbstractBACKGROUNDThe presence of micro‐pollutants in conventional wastewater treatment plants raises environmental concerns due to their insufficient removal. Non‐biological methods are needed to treat such compounds and this work demonstrates the use of electrochemical oxidation for the degradation of the drug dexamethasone (DEX).RESULTSA cell consisting of a boron‐doped diamond anode and a stainless steel or carbon cloth cathode was employed, with Na2SO4 being the electrolyte. DEX degradation rate, at the low level of mg L−1 (0.25–2 mg L−1), increases with increasing current (0.02–0.2 A m−2), as well as in the presence of sodium persulfate (50–250 mg L−1); the latter is electrochemically activated to produce additional oxidants and enhances degradation in a synergistic way. A rate constant of 0.194 min−1 was recorded for 0.5 mg L−1 DEX degradation at 0.2 A m−2 with 150 mg L−1 persulfate. The water matrix had little effect on performance compared to experiments in pure water; the only exception was the presence of chloride (50–250 mg L−1), which substantially improved rates due to the formation of active chlorine species (up to about five times). Carbon cloth accelerated DEX removal by up to three times compared to stainless steel and this was partly due to its adsorptive capacity; similarly, reactions involving DEX transformation products (TPs) also occurred faster. Seven TPs were identified and profiles were followed; reaction pathways involve hydroxylation, oxidation, decarboxylation and ring‐opening reactions, followed by fluorine release in the liquid phase.CONCLUSIONA hybrid technology based on electrochemical oxidation and persulfate activation is proposed for the treatment of residual pharmaceuticals in environmental matrices. © 2021 Society of Chemical Industry (SCI).

Pt Nanoclusters Anchored on Hollow Ag-Au Nanostructures for Electrochemical Oxidation of Methanol

The synthetic method of Pt nanocluster-anchored hollow Ag-Au nanostructures and measurements of their electrocatalytic properties for methanol oxidation reaction (MOR) are reported here. In this synthesis, uniform Ag nanospheres were prepared by reduction of silver nitrate (AgNO3) with sodium borohydride (NaBH4) and then hollow Ag-Au nanostructures were synthesized via galvanic replacement of the as-prepared Ag nanospheres with Au3+. Finally, the reduction of potassium tetrachloroplatinate (II) (K2PtCl4) with ascorbic acid was performed to deposit Pt nanoclusters on the surface of hollow Ag-Au nanostructures. The hollow interior of Pt nanocluster-anchored Ag-Au nanostructures and change in the size of Pt nanoclusters by varying the injected molar ratio of Pt/Au were observed by transmission electron microscopy (TEM). Moreover, other morphological, compositional, and optical information of the obtained nanoscale materials were analyzed by X-ray diffraction analysis (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and ultraviolet-visible spectroscopy (UV-vis). The electrocatalytic ability of the obtained Pt nanocluster-anchored hollow Ag-Au nanostructures toward MOR was confirmed by the results of cyclic voltametric (CV) measurements. The ease of three-step synthetic strategy and good electrocatalytic performance of the Pt nanocluster-anchored hollow Ag-Au nanostructures displayed their promising potential in the use of electrochemical oxidation of methanol.

Cellular Reference Materials for DNA Damage Using Electrochemical Oxidation.

Reference materials are needed to quantify the level of DNA damage in cells, to assess sources of measurement variability and to compare results from different laboratories. The comet assay (single cell gel electrophoresis) is a widely used method to determine DNA damage in the form of strand breaks. Here we examine the use of electrochemical oxidation to produce DNA damage in cultured mammalian cells and quantify its percentage using the comet assay. Chinese hamster ovary (CHO) cells were grown on an indium tin oxide electrode surface and exposed 12 h to electrochemical potentials ranging from 0.5 V to 1.5 V (vs Ag/AgCl). The resulting cells were harvested and analyzed by comet and a cell viability assay. We observed a linear increase in the percentage (DNA in tail) of strand breaks along with a loss of cell viability with increasing oxidation potential value. The results indicate that electrochemically induced DNA damage can be produced in mammalian cells under well-controlled conditions and could be considered in making a cellular reference material for the comet assay.

Azo dyes degradation and mutagenicity evaluation with a combination of microbiological and oxidative discoloration treatments

This work evaluated the degradation of the Acid Blue 161 and Procion Red MX-5B dyes in a binary solution by the filamentous fungus Aspergillus terreus and the yeast Saccharomyces cerevisiae in systems with and without electrochemical oxidation as the pretreatment process. UV–Vis spectrophotometry, high-performance liquid chromatography with (HPLC), Fourier transform infrared (FT-IR) spectroscopy and Salmonella/microsome assay (Ames test) were applied towards the degradation analysis of the dyes. Adsorption tests with white clay immobilized on alginate were also conducted after the discoloration treatments to remove intermediate metabolites formed during the degradation of the dye molecules. The discoloration treatments led to the complete color removal of the solutions in all the systems tested. The clay demonstrated affinity for the metabolites formed after discoloration treatments, the removal rates were variable, but the all systems has proved efficient. The Salmonella/microsome assay (Ames test) with strains TA98 and TA100 in the absence and presence of exogenous metabolism (S9 microsomal system, Moltox) revealed that the initial molecules and by-products of the metabolism of the dyes were direct mutagens. The electrochemical/A. terreus/clay system was able to discolor the solutions and transform the direct mutagens into non-mutagenic compounds in addition to reducing the mutagenic potency of the pro-mutagens to the Salmonella strain TA100/S9, which demonstrates the high efficiency of this system with regard to discoloring and degrading azo dye molecules and their by-products. Therefore, this study showed that although not having standard treatment system for this type of pollutant, the combination of treatments can be considered promising. The use of electrochemical oxidation along with microbiological treatment may lead to the degradation and mineralization of these compounds, reducing or eliminating the environmental impact caused by the improper disposal of these dyes in aquatic environments.

Influence of Molecular Size on the Electrochemical Oxidation of Fractioned Cork Boiling Wastewater

AbstractThe performance of electrochemical oxidation (EO) using a boron doped diamond (BDD) anode was assessed for cork boiling wastewater (CBW) molecular size fractions of >100 kDa, 50–100 kDa, 20–50 kDa, 10–20 kDa and <10 kDa, obtained through sequential use of ultrafiltration (UF) membranes. The best EO results were found in the experiments performed with no addition of supporting electrolyte and at the lowest applied stirring speed, the more economical and environmentally friendly conditions. The highest EO treatment efficiency was observed for the fraction >100 kDa, which presented also the highest organic load. EO treatment led to an increase in the biodegradability of the fraction >100 kDa and to a decrease in the biodegradability of the fraction <10 kDa. Moreover, samples toxicity was not affected by the EO process, suggesting that the treated samples can be forwarded to biological post‐treatment processes. UF fractionation showed to be advantageous in combination with EO, since it enables the selective use of EO where it is more effective regarding biodegradability and current efficiency.

Electrochemical mineralization and detoxification of naphthenic acids on boron-doped diamond anodes.

Electrochemical oxidation (ELOX) with boron-doped diamond (BDD) anodes was successfully applied to degrade a model aqueous solution of a mixture of commercial naphthenic acids (NAs). The model mixture was prepared resembling the NA and salt composition of oil sands process-affected water (OSPW) as described in the literature. The initial concentration of NAs between 70 and 120mg/L did not influence the electrooxidation kinetics. However, increasing the applied current density from 20 to 100A/m2 and the initial chloride concentration from 15 to 70 and 150mg/L accelerated the rate of NA degradation. At higher chloride concentration, the formation of indirect oxidative species could contribute to the faster oxidation of NAs. Complete chemical oxygen demand removal at an initial NA concentration of 120mg/L, 70mg/L of chloride and applied 50A/m2 of current density was achieved, and 85% mineralization, defined as the decrease of the total organic carbon (TOC) content, was attained. Moreover, after 6h of treatment and independently on the experimental conditions, the formation of more toxic species, i.e. perchlorate and organochlorinated compounds, was not detected. Finally, the use of ELOX with BDD anodes produced a 7 to 11-fold reduction of toxicity (IC50 towards Vibrio fischeri) after 2h of treatment.

Reduction in energy consumption of electrochemical pesticide degradation through combination with membrane filtration

A significant challenge for large-scale use of electrochemical oxidation (EO) is high energy consumption, and for EO to become accepted as a standard technique, the amount of energy consumed in the process must be reduced.In this study, it was investigated how the energy consumption of EO could be lowered by combining the process with membrane filtration, in a setup where EO was applied to the membrane retentate stream. Use of two types of membranes, a nanofiltration (NF) and a reverse osmosis (RO) membrane, was investigated, and to provide realistic estimates on the energy consumption of the treatment, natural groundwater spiked with the pesticide residue 2,6-dichlorobenzamide (BAM) was used as matrix in the experiments. To understand the effect of the membranes on the energy consumption, their effect on the EO degradation efficiency was also determined.The results showed that membranes significantly reduced the energy consumption of the EO processes. Using the RO membrane with a recovery of 90%, the energy consumption of the combined EO and membrane setup used 95% less energy (0.96kWh/m3) compared to the stand-alone EO treatment (18.5kWh/m3). The reduction in energy consumption was found to be a result of primarily two factors; (1) a smaller volume of water was in need in the energy intensive EO treatment, and (2) the high rejection of chloride by the RO membrane increased the rate of degradation through mediated active chlorine oxidation in the membrane retentate. It was not possible to obtain the same positive benefits using the NF membrane, which was mainly due to a lower chloride rejection and a too low rejection of BAM. The investigation showed that combining RO filtration with EO of the contaminants in the concentrate provides a promising strategy for the dissemination of advanced oxidative treatment techniques in larger scale and actual use for protection of the environment.

Treatment of Alkaline Waste Water Generated by the Hydrolysis of Rice Husk

This article shows the results of research on finding ways to purify waste water produced by alkaline hydrolysis of rice waste - rice husk. Two methods were used: baromembrane filtration and electrochemical oxidation of organic substances. It was found that in the results of baromembrane processing of hydrolyzate on the membranes mainly stay silicon compounds partially sorbing organic substances contained in the feedstock. Through the membranes there pass the major part of microbiologically oxidated organic matter, so its difficult to reach the required waste water treatment stage. The use of electrochemical oxidation of organic substances extracted by alkaline hydrolysis of rice husks into a solution allows more qualitatively treat the solution. A range of indicators (chemical oxygen demand, permanganate demand, polyphenols) evaluating the content of organic compounds in the desilicated solution showed that in order to remove them effectively enough electrolyte concentration of sodium chloride is 4 g L-1, formed by the desilication and dilution of the solution with the distilled water 1:10.

Advanced Electrochemical Oxidation of Ultrafiltration Permeates from Cellulose Bleaching Effluents

AbstractThis paper reports experimental results on the use of electrochemical oxidation to reduce the organic load in ultrafiltration permeates from cellulose bleaching effluents. Alkaline and acid bleaching effluents from industrial production of ECF bleached kraft cellulose from pinewood, were treated by ultrafiltration at 20 kDa, 10 kDa and 1 kDa, using a laboratory scale high performance UF unit. Electrochemical treatment of UF permeate was conducted in a dual cell electro-reactor, featuring stainless steel cathode, and graphite, DSA-RuO2 and DSA-Pt anodes. Experiments were conducted under potentiostatic conditions, at 2V with current densities in the range 1-5 A/m

Competition between electrochemical advanced oxidation and electrochemical hypochlorination of acetaminophen at boron-doped diamond and ruthenium dioxide based anodes

This work was undertaken to distinguish four pathways for the electrochemical oxidation of acetaminophen as a model organic substrate: (i) direct electron transfer from the substrate to the anode, (ii) reaction of the substrate with HO• at boron-doped diamond anodes, (iii) non-radical (two-electron) oxidation of the substrate at Ti/RuO2 anodes, and (iv) electrochemical hypochlorination if Cl– is present. Pathway (i) was isolated as a slow reaction when boron-doped diamond (BDD) was used as the anode in the range of water stability, whereas in the corresponding reaction with Ti/RuO2 only pathway (iii) could be detected. Pathway (ii) predominated for BDD in the potential range of water oxidation, and was the only mechanism leading to mineralization of the substrate. Comparison between chemical hypochlorination and electrochemical oxidation at Ti/RuO2 in the presence of chloride ion indicated that the latter process principally involves mediated hypochlorination. Oxidation at boron-doped diamond anodes in the presence of chloride was the most complex mechanistically, with competition between hypochlorination and the electrochemical “advanced oxidation process”; this led to the formation of chlorinated byproducts. The observation of mineralization under these conditions demonstrated cross-over between reaction pathways (ii) and (iv), even though hypochlorination appeared to be the initial pathway for loss of acetaminophen. The presence of chloride ion did not significantly retard mineralization of acetaminophen in the initial stages of oxidation, but significantly increased the energy requirement for complete mineralization. The results are discussed in the context of the use of electrochemical oxidation in waste management.

Making the most of your ultrasonic system: Understanding critical variables can help maximize the return on your cleaning system investment

Titanium and its alloys are the most commonly used materials in biomedical applications. Among years, the number of Ti-based alloys, mainly binary and ternary, used as implants increased significantly. Naturally, scientists are still searching for methods of improvement of the mechanical, protective, and biological properties of such materials. Hence modification of alloys with the use of electrochemical oxidation (anodization) which allows for the fabrication of nanostructural oxide layers on the metal surface gained much interest. Moreover nanotopography of these layers allows not only to mimic the structure of natural bone, enhancing cell’s adsorption but also gives various possibilities of their impregnation with antibacterial agents, drugs, or growth factors. Therefore the synthesis of multifunctional and biocompatible materials is possible. This chapter aims to give an overview of the influence of anodization parameters on the morphology of anodic oxide layers on titanium alloys. Overall the corrosion resistance of such materials, their antibacterial properties as well as biocompatibility and several surface modifications enhancing the biological response of the potential implant are presented. Finally, a summary of the most promising strategies when it comes to implantable materials is given.

Synthesis of Dibenzocyclooctadienes by Anodic Oxidation

Abstract the use of electrochemical oxidation was applied to the synthesis of dibenzocyclooctadiene lactones related to steganacin skeleton. This reaction, performed with compounds 1 and 2, led to results comparable with the oxidation with RuTFA, TTFA and VOF3.

ChemInform Abstract: New Synthesis of 4‐Acetoxy‐2‐azetidinones by Use of Electrochemical Oxidation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New synthesis of 4-acetoxy-2-azetidinones by use of electrochemical oxidation

4-Acetoxy-2-azetidinone was synthesized from 4-carboxy-2-azetidinone by Kolbe-type electrolysis. Optically pure 4-acetoxy-3-[1-(t-butyldimethylsiloxy)ethyl]-2-azetidinone, which is an important intermediate for the synthesis of thienamycin, and (+)-PS-5 were synthesized by use of this method.

ChemInform Abstract: Ring Construction of Bicyclic γ‐Lactams by Use of Electrochemical Oxidation.

AbstractElectrolysis of pyroglutamic acid (I) in the presence of sodium acetate (II) results in decarboxylative substitution to give the 5‐acetoxypyrrolidone (III).

ChemInform Abstract: Electrosynthesis of Porphyrins from a,c‐Biladienes.

AbstractFor the first time it is shown that the Cu(II) oxidant commonly used to cyclize biladienes to porphyrins can be eliminated by use of electrochemical oxidation at 0.8 V. From (Ia) the porphyrin (IIIa) is obtained (yield 42%) and the Zn(II) complex of (Ia) yields the Zn(II) porphyrin of (IIIa) (40%).

Ring Construction of Bicyclic g-Lactams by Use of Electrochemical Oxidation

α-Acetoxy lactam derivatives generated from α-carboxy lactams by the use of electrochemical oxidation in the presence of AcONa in MeCN-AcOH were useful intermediates for the synthesis of bicyclic lactams

ChemInform Abstract: New Synthesis of 4‐Acetoxy‐2‐azetidinones by Use of Electrochemical Oxidation.

AbstractElectrochemical oxidation of the azetidinones (I), (IV), and (V) in the presence of acetic acid (II) gives the 4‐acetoxyazetidinones (III) or (VI).