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Linoleic acid (LA) was investigated as an electron transfer catalyst in biomimetic lignin degradation with an electrolytic mediator system (EMS). Initial attempts of electro-oxidations of synthetic lignin, guaiacyl (G)-type dehydrogenation polymer (G-DHP), with LA alone at 0.8 V and 1.8 V, resulted in limited G-DHP conversion, suggesting that LA-mediated EMS is not effective when LA was used alone. Next, electro-oxidations of G-DHP with LA with O2-sparging as well as in the presence of co-catalysts, such as p-coumaric acid (PCA), tris(2,2′-bipyridine) iron(II) [Fe(bpy)3], and 1-hydroxybenzotriazole (HBT) were performed. The combined use of oxygen and co-catalysts appeared to be effective to promote G-DHP conversion. In particular, G-DHP conversion proceeded effectively in the electro-oxidation with LA/HBT at 0.6 V, as demonstrated by structural analysis of the electrolysis residues using nuclear magnetic resonance. HBT was also found to be a vital mediator when used alone in the present system. Overall, the combined use of oxygen and co-catalysts was essential for the EMS oxidation with LA, as reported in laccase mediator system (LMS) oxidation with LA. [ABSTRACT FROM AUTHOR]

The release of anaerobically digested dairy wastewater (ANDDW) without a treatment can lead to severe environmental pollution, prompting the exploration of effective and sustainable treatment methods. Amidst various wastewater treatment approaches, the electro-oxidation (EO) process is considered as a promising, clean, and adaptable solution. In this study, the major operational parameters viz. current density, electrolyte concentration, treatment time, and mixing speed of an EO comprising Ti/PbO2 anode and stainless-steel cathode, were optimized using response surface methodology (RSM) for efficient removal of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), orthophosphate (OP), total nitrogen (TN), and total Kjeldahl nitrogen (TKN) from ANDDW. Optimal conditions were identified as a current density of 90 mA cm−2, 0.08% electrolyte concentration, 180 min treatment time, and 400 rpm mixing speed. Under the optimum conditions, the COD, NH3-N, TP, OP, TN, and TKN removal efficiencies were 78.36, 63.93, 87.41, 92.39, 67.01, and 81.42%, respectively. Furthermore, the reaction rate followed the first-order kinetic model for the pollutants removal with correlation coefficients (R2) close to 1. The findings highlight the potential of using the EO process to treat high pollutant-laden ANDDW and encourage further studies to confirm the corresponding outcomes on a pilot scale. [ABSTRACT FROM AUTHOR]

The present research aimed to explore the durability of MMO electrodes through electro-oxidation (EO) in purifying secondary treated actual sewage wastewater using batch and pilot-scale setups. The main aim is to inactivate bacteria in sewage treatment plants before they are released into the environment, thus contaminating water and soil. Process parameters such as current density (j), NaCl dose (n), and treatment time (t) were optimized using response surface methodology in a lab-scale EO reactor under batch conditions. The results showed that optimization of current density at 5.90 mA/cm2 and NaCl concentration at 1.31 g/L led to 93.90% of bacterial inactivation (Q1) within 8 min of treatment and 0.48 kWh/m3 energy consumption (Q2). Biological analysis was conducted to validate bacterial cell destruction and count coliform bacteria in the EO-treated sewage wastewater. XRD, cyclic voltammetry studies, and FE-SEM/EDS analysis were done to confirm the MMO anode's durability and stability after 100 recycles. The study prioritized bacterial inactivation along with organic matter degradation. Besides that, a small pilot-scale study on the actual sewage wastewater with a volume of 10–50 L was done in batch mode under previously optimized conditions to analyze the efficacy of the MMO anodes in terms of bacterial inactivation. [ABSTRACT FROM AUTHOR]

Animal farming wastewater is one of the most important sources of ammonia nitrogen (NH4+-N) emissions. Electro-oxidation can be a viable solution for removing NH4+-N in wastewater. Compared with other treatment methods, electro-oxidation has the advantages of i) high removal efficiency, ii) smaller size of treatment facilities, and iii) complete removal of contaminant. In this study, a previously prepared DSA (W, Ti-doped IrO2) was used for electro-oxidation of synthetic mariculture and livestock wastewater. The DSA was tested for chlorine evolution reaction (CER) activity, and the reaction kinetics was investigated. CER current efficiency reaches 60–80% in mariculture wastewater and less than 20% in livestock wastewater. In the absence of NH4+-N, the generation of active chlorine follows zero-order kinetics and its consumption follows first-order kinetics, with cathodic reduction being its main consumption pathway, rather than escape or conversion to ClO3−. Cyclic voltammetry experiments show that NH4+-N in the form of NH3 can be oxidized directly on the anode surface. In addition, the generated active chlorine combines with NH4+-N at a fast rate near the anode, rather than in the bulk solution. In electrolysis experiments, the NH4+-N removal rate in synthetic mariculture wastewater (30–40 mg/L NH4+-N) and livestock wastewater (~ 450 mg/L NH4+-N) is 112.9 g NH4+-N/(m2·d) and 186.5 g NH4+-N/(m2·d), respectively, which is much more efficient than biological treatment. The specific energy consumption (SEC) in synthetic mariculture wastewater is 31.5 kWh/kg NH4+-N, comparable to other modified electro-catalysts reported in the literature. However, in synthetic livestock wastewater, the SEC is as high as 260 kWh/kg NH4+-N, mainly due to the suppression of active chlorine generation by HCO3− and the generation of NO3− as a by-product. Therefore, we conclude that electro-oxidation is suitable for mariculture wastewater treatment, but is not recommended for livestock wastewater. Electrolysis prior to urea hydrolysis may enhance the treatment efficiency in livestock wastewater. [ABSTRACT FROM AUTHOR]

In this study, the electro-oxidation reaction of ethanol over Pd–Cu supported on Cu porphyrin (TPPCu) was investigated. The catalyst was synthesized using the microwave-assisted polyol method and physicochemically characterized by XRD, XPS, SEM, EDS, TEM, EDAX, UV–Vis, FTIR, and RBS. A Cu-enriched catalyst with Cu3Pd, Pd,Cu, and TPPCu phases was identified using XRD and XPS. However, according to the RBS results, the catalytic surface was enriched with Pd, indicating that the interaction between TPPCu and Pd–Cu allowed the presence of Pd on the surface, thus enhancing the catalytic response of the material. This synthesis prevented the deprotonation of porphyrin on the electrocatalyst, as confirmed by XPS analysis. Electrochemical studies based on cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the response of the catalyst to variations in the scan rate and increasing ethanol concentration. The electrochemical response of PdCu/TPPCu improved with an increasing number of cycles, indicating improved mass transport, thus improving its electrochemical response and tolerance to CO contamination. This catalyst exhibited a high electroactive surface area of 49.4 m2/g, which could be related to the presence of TPPCu as a support. The behavior of the catalyst on the anode of a fuel cell fed with ethanol, bioethanol, and bioethanol residues was evaluated. [ABSTRACT FROM AUTHOR]

In this study, the removal of indigo dye, which is used in the denim industry, by using the electro-oxidation method was investigated. Experiments were carried out using Sn/Sb/Ni–Ti anode and Pt–Ti cathode electrodes of indigo dye aqueous solution with an initial concentration of 100 mg/L, which was prepared synthetically in the laboratory. In the first stage of the study, appropriate support electrolyte (NaCl, KCl, Na2SO4, K2SO4) detection investigations were carried out. As a result of the trials, NaCl electrolyte was chosen as the supporting electrolyte type because it is both affordable and has high removal efficiency compared to other electrolytes. Color and COD removal were established according to the effective factors (pH, current density, supporting electrolyte concentration and electro-oxidation time) for the electro-oxidation method using the central composite design (CCD) based response surface methodology (RSM). The design consists of four components and seven central experiments, each with three levels. According to the RSM result, ideal conditions were pH 11, current density 51.01 mA/cm2, supporting electrolyte concentration 1565.66 mg/L and duration 120 min. In ideal conditions, COD removal was determined as 97.43% and color removal as 98.93%, while energy consumption was determined as 17.49 kWh/kg COD. In the last stage of the study, pilot-scale tests were carried out in a spherical polyethylene (PE) tank with a bottom diameter of 65 cm and a height of 157 cm. Color and COD removal efficiencies obtained from the pilot scale under optimum conditions were calculated as 95.26% and 92.16%, respectively. [ABSTRACT FROM AUTHOR]

The development of economically viable anode catalysts for the alcohol oxidation reaction (AOR) has been a long-standing challenge in direct alcohol fuel cells (DAFCs). A series of Pd–Ag nanoparticles embedded in mesoporous carbon were fabricated in this study using a green approach that did not require the use of a surfactant, which exhibited better catalytic properties for AOR. Experiments and DFT calculations reveal that the d-band center of Pd is influenced by both strain and ligand effects, with the ligand effect predominating. The electrochemical studies demonstrated that the composite-optimized Pd–Ag alloy at a Pd/Ag molar ratio of 1:1 was the highest in terms of ethanol oxidation (EOR) and ethylene glycol oxidation (EGOR) catalytic activity. The mass activities of Pd1Ag1/MC for EOR and EGOR were 7921 mA mg−1 and 11,520 mA mg−1, respectively, which were 3.77 and 5.3 fold greater than Pd/C. The impressive performance of Pd1Ag1/MC catalyst could be attributed to the vital roles of the unique mesoporous structure of carbon sphere with abundant self-doping defect and the boosting effect of Ag (benefit from optimized d-band electronic structure and bi-functional mechanism). The present simple method of synthesizing low-cost, easy-to-use, and high-performance catalysts contributes to the exploration of the large-scale practical applications of direct alkaline alcohol fuel cells. [ABSTRACT FROM AUTHOR]

This study investigated the nano-metals (Cu, Ni, Co or Fe) and carbon composite catalysts for electro-oxidation of ethylene glycol (EG) both in acidic and basic medium. The physical surface area varied between 379 and 615 m2 g−1, while the electrochemical surface area was in the range of 20.8–44.3 m2 g−1. The average metal size ranged from 7.8 to 16.3 nm confirming the nano-metal structure. The work function values of different electrocatalysts were between 4.21 and 4.56 eV. The highest current density of 11 mA cm−2 was observed for 20Ni-AC in basic medium at 1 V in presence of EG, followed by that of 20Cu-AC (6.9 mA cm−2), 20Co-AC (6.6 mA cm−2) and 20Fe-AC (5.9 mA cm−2). The current density of the composite catalysts was much enhanced compared to individual components. The performance was directly related to the electrochemical surface area of the catalysts as well as work function values, and ability to form higher oxidation states of the catalysts. Time constants (τ1, τ2) obtained from EIS analysis revealed that the electrochemical process was the slower step in both acidic and basic mediums. The 20Ni-AC showed structural stability as anode electrode. [ABSTRACT FROM AUTHOR]

Electro-oxidation (EO) is an effective wastewater treatment technology but faces several challenges regarding its feasibility and economic acceptance, namely high operational and maintenance costs, insufficient oxidizing agent production, etc. The present study attempts to intensify the in situ EO treatment potential in a membraned and membrane-less electrochemical reactor (ECR) to treat blackwater (BW) at a single household (SHH) level by optimizing the dosing percentage of non-iodized sodium chloride (NaCl) in BW. The applied current density and electrolysis time were optimized for effective EO to maintain the total residual chlorine in the treated effluent within 5 ppm (WHO discharge limit). Comparatively, membrane-less ECR showed a better overall treatment than the membraned ECR. The membrane-less ECR was pre-integrated with vertical flow constructed wetland (VFCW) and post-integrated with the polyamine resin column. The average percentage removal of chemical oxygen demand, total ammoniacal nitrogen, nitrates, and ortho-phosphates achieved by the integrated treatment system was 87.95 ± 0.7%, 87.5 ± 2.1%, 95.99 ± 0.3%, and 99.82 ± 0.05%, respectively. The complete removal of Coliform with acceptable effluent pH (7.65 ± 0.2) was obtained in 1 h electrolysis time at 40.03 Am−2. The energy requirement was 6.24 ± 0.12 KWhm−3. The cost of the treatment was 36.13 INR m−3 (0.46 USD m−3) which is significantly lower than any treatment schemes that employ EO, thus making the integrated treatment system a potential technology for scale-up and real-time application. [ABSTRACT FROM AUTHOR]

In December 2019, the world experienced a new coronavirus, SARS-CoV-2, causing coronavirus disease 2019 originating from Wuhan.The virus has crossed national borders and now affects more than 200 countries and territories. Hydroxychloroquine has been considered as a drug capable of treating COVID-19. The objective of this work is to establish a simple platform for electrocatalytic detection of hydroxychloroquine in human urine samples and pharmaceutical samples (tablets) using a ZnO@CPE sensor constructed by simple and inexpensive hydrothermal methods using a square wave voltammetry method. The best results are obtained in a PBS electrolyte with irreversible behavior of the hydroxychloroquine complement and controlled by diffusion coupled with absorption phenomena. The ZnO@CPE shifts the oxidation potential of hydroxychloroquine with the formation of a single very intense peak at the position of Epa = 0.5 V/(vs Ag/AgCl) with a shift is ΔEp = 0.1 V(vs Ag/AgCl) compared to the unmodified electrode. The obtained ZnO@CPE hybrid nanocomposite was characterized by different techniques and showed excellent electrocatalytic activity and higher active surface area compared to the bare carbon paste electrode. Under the optimized experimental conditions, the ZnO@CPE sensor showed good analytical performance for the determination of trace amounts of hydroxychloroquine, a wide linearity range from 10–3 M to 0.8 × 10–6 M with a very low detection limit in the range of 1.33 × 10–7 M, satisfactory selectivity, acceptable repeatability and reproducibility. The calculated recovery and coefficient of variation for the two samples analyzed are very satisfactory, ranging from 97.6 to 102% and 1.2 to 2.3% respectively. The proposed applied method and the fabricated sensor offer the possibility to analyze traces of hydroxychloroquine in real human urine and water samples. Strategy for the electro-oxidation reaction of hydroxychloroquine on the electro-catalytic surface of the ZnO@Carbon graphite electrode and real-time detection of hydroxychloroquine. [ABSTRACT FROM AUTHOR]

As a result of the rapid development of industry and technology, a great increase has been observed in the use of chemicals and toxic substances harmful to the environment, especially in the last 20 yr. The harmful effects of industrial wastewater, which are formed as a result of the use of chemical and toxic substances as raw substances and by products in many technology branches, adversely affect the environment. Traditional treatment methods are quite inadequate in the treatment of industrial wastewater. Water pollution is one of the most important environmental problems of today. Since water is the most basic need of living things and the source of great economic activities, it is an indispensable resource for the continuation of living and non-living life. Acid dyes, one or more in the molecule contain a sulfonic acid group or a carboxylic acid group. Acid dyes are chemically classified as anionic dyes. Direct metal-complex and reactive dyestuffs containing sulfonic acid groups are also anionic. Basic dyes are in the form of hydrochlorides of organic bases and are found in the colored part of the cationic group dye. Basic dyes, contain N or S atoms as positive charge carriers. Different chemical, physical and biological processes such as chlorination, ozonation, adsorption and microfiltration are widely used in cleaning the environments where industrial wastes are present. However, in all of these methods organic substance can be removal by transferring it from one phase to another. However, due to increasing environmental pollution, the treatment process has changed to develop new methods that can decompose organic substances into CO2 and H2O instead of transferring them from one phase to another. Hybrid systems in which different oxidation processes are applied simultaneously in the same electrochemical cell, are widely used today in order to increase the efficiency of the electrochemical methods. [ABSTRACT FROM AUTHOR]

Electro-activated persulfate has displayed good performance in the oxidation of antibiotic pollutants in wastewater. However, high power consumption and the introduction of excessive sulfate ions hinder the application of this technology. This research provided a novel strategy for the applications of small power supply and simple devices in antibiotic pollutant treatment. It has been confirmed that sulfate radical ( SO 4 ∙ - ) could be generated at the boron-doped diamond (BDD) anode in both low and high current conditions. This study proposed a novel low current density electrochemical technology assisted by peroxymonosulfate (PMS) for the degradation of antibiotics. Adding 1 mg/L PMS at current density as low as 1.25 mA/cm2 increased the electro-oxidation rates of ciprofloxacin 5-fold from 1.92 ± 0.67 h−1to 9.70 ± 0.10 h−1. According to the Butler-Volmer equation, the introduction of PMS changed the mechanism of electrode reactions, thermodynamic properties of the system therefore changed. The electron spin resonance (ESR) test has confirmed that hydroxyl radical (•OH), SO 4 ∙ - , and singlet oxygen (1O2) are all generated in low current electrochemical systems. Quenching experiments illustrate that both radical and non-radical ways play essential roles in electro-oxidation processes. The contribution rates of •OH, SO 4 ∙ - , and 1O2 were 15.6%, 33.2%, and 40.5%, respectively. An oxidation peak was observed in cyclic voltammetry (CV) around +1.2 V, indicating that PMS electrolyte may drive oxidation at this potential. Besides, the reaction pathways of ciprofloxacin were speculated. Four transformation pathways including stepwise piperazine ring cleavage, OH/F substitution, cyclopropane ring cleavage, and decarboxylation were proposed for ciprofloxacin degradation. [ABSTRACT FROM AUTHOR]

Leachate concentrate is a highly complex effluent. This study compares the treatability of leachate concentrate by synergistic radical-based processes ((persulfate (PS) + O3 (ozone) + electrooxidation (EO)), (O2 state + zero-valent aluminum (ZVAl)) and (ZVAl + PS)). Process conditions for high color removal efficiency were optimized using the randomized response surface design. Under optimum conditions, operation cost (€/L wastewater), color and COD removal efficiency (%), and increase in BOD5/COD ratio (%) were determined as 1.1000, 84 and 50.66, and 195.20 for (PS + O3 + EO), 1.8425, 56.67 and 41.5, and 50 for (O2 state + ZVAl), and 4.1538, 70 and 64, and 147.61 for (O2 state + ZVAl + PS). Using the PROMETHEE approach, three processes were evaluated for operational cost, biodegradability, organic matter, and color removal criteria, and the most suitable process was selected. Process preference order was determined as (PS + O3 + EO) > (O2 state + ZVAl + PS) > (O2 state + ZVAl). The optimum operating conditions for (PS + O3 + EO) process were determined as pH of 9.96, duration of 146.69 min, PS of 4.02 g/L anion, electrode type of RuO2-IrO2, and ozone dose of 65.99%. [ABSTRACT FROM AUTHOR]

In this paper, a sensitive electroanalytical sensor by reduced graphene oxide (RGO) modified carbon paste electrode (CPE) was established for the determination of darunavir (DRV). For this goal, RGO was firstly prepared and recognized by different techniques. The oxidation potential of DRV was meaningfully decreased on the RGO/CPE surface versus CPE, and its anodic signal was amplified. In the optimal condition, the calibration curve for DRV was plotted from the DPV method. The linear dynamic ranges (LDR) and limit of detection (LOD) were achieved to be 0.5–900 µM and 0.41 µM, respectively. The diffusion coefficient and catalytic rate constant were calculated to be 1.02 × 10–5 cm2 s−1 and 8.4 × 106 cm3 mol−1 s−1, respectively. In addition, the practical presentation of RGO/CPE was performed by measuring the DRV in the tablet with good recovery. The suggested process is easy, cheap, and fast and might be utilized as a significant analytical tool in the quality control of the pharmaceutical production. It is worth mentioning that this study is the first to specifically address the electrochemical measurement of darunavir, making it novel in its field. [ABSTRACT FROM AUTHOR]

In the present study, the treatment of slaughterhouse wastewater (SWW) by electro-oxidation method and the energy consumption of the system during the process were investigated. The removal of chemical oxygen demand (COD), color, turbidity, and suspended solids (SS) from wastewater is emphasized. Ti/IrO2/RuO2 was used as the anode material and uncoated titanium was used as the cathode material in the experiments. The experiments were carried out in a glass reactor; the supporting electrolyte (SE) type, concentration, initial pH value, and current density were studied under different conditions. Na2SO4, NaNO3 NaCl, and KCl salts have been used as SE. Salt studies were carried out at 0.1, 0.2, 0.3 and 0.4 M concentrations. The current density was studied at 4.06 mA/cm2, 6.09 mA/cm2, 8.12 mA/cm2, 10.15 mA/cm2, 12.18 mA/cm2. Studies have been carried out at pH 3–9–11 and natural wastewater pH values. The optimum conditions to be used in electro-oxidation of SWW with high organic content have been determined. The results have revealed that as the current density increased, the efficiency increased, and the highest removal was achieved at the natural pH value of the NaCl salt. Studies have shown that color, turbidity, and SS removal for SWW is approximately 90%. COD was found to be 66.46% at the lowest current density. The energy consumption in the selected optimum conditions was found to be 183.6 kWh/m3. [ABSTRACT FROM AUTHOR]

The nanoparticles (NPs) of Ni with different sizes endows its distinctive physical and chemical properties, which represents a typical strategy for the development of high-performance catalysts. However, the size effect of metallic Ni-NPs on electrocatalytic performance remains ambiguous. Herein, the Ni-NPs with different sizes supported on nitrogen doped carbon (NC) has been synthesized by controlling the pyrolysis temperature, leading to the synthesis of Ni@NC-500 (8.3 nm), Ni@NC-280 (1.9 nm) and Ni@NC-200 (1.0 nm). The electrooxidation of benzyl alcohol (BA) over these nanocatalysts shows the yield of benzoic acid was 99%, 82%, 55% on Ni@NC-280, Ni@NC-200 and Ni@NC-500, respectively. The experimental and theoretical simulation demonstrate that the difference in the adsorption strength of reactant molecules by Ni-NPs is responsible for their different performance, where the Ni@NC-280 exhibits an optimal adsorption configuration between Ni@NC-280 electrode and BA. This work provides a new angle for designing and synthesizing efficient electrocatalysts, which may be extended to the exploration of various promising electrocatalytic systems. [ABSTRACT FROM AUTHOR]

Diazinon, an organophosphorus pesticide, widely used in agricultural activities, can be effectively degraded in aqueous solutions via advanced oxidation processes. Electrochemical oxidation is a promising technique for the degradation of recalcitrant organic micropollutants in water. Thus, this study evaluated the pesticide diazinon degradation by anodic oxidation. To carry out the experiments, a synthetic solution of diazinon was used, with an initial concentration of 40 mg L−1. Two types of electrodes were evaluated, a dimensionally stable anode type, with RuO2–IrO2 composition, and a boron-doped diamond (BDD) electrode. In addition, two supporting electrolytes (NaCl and Na2SO4), the electrolyte concentration, current density and also energy consumption were evaluated. All configurations were able to promote the degradation of total organic carbon. The anodic oxidation for the degradation of diazinon was more efficient with the BDD electrode, reaching 97.5% of diazinon removal after 180 min with 25 mM of Na2SO4, a current density of 42 mA cm−2 and pH 3. [ABSTRACT FROM AUTHOR]

Two electrochemical sensors based on modified glassy carbon electrodes with carbon nanostructures as graphene (GCE–EG) and carbon nanotubes (GCE–CNT) were evaluated for morpholine analysis. The carbon nanostructures were obtained and characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and cyclic voltammetry. All spectroscopic and microscopic techniques confirmed the procurement of graphene and CNT. The electrochemical studies proved the efficient behaviour of both electrodes GCE–EG and GCE–CNT in sensing and detection of morpholine via differential pulse voltammetry. The area of the anodic peaks was correlated with the concentration of the analyte. It was observed that the implementation of a thin film of EG and CNT on the GCE promoted the electrocatalytic activity towards morpholine electro-oxidation, and a considerable increase in the corresponding oxidation peak was observed in both cases. Theoretical detection limits of 1.0 and 1.3 mg l–1 were obtained for GCE–EG and GCE–CNT, respectively. These merit figures, both satisfactorily meet the requirements of the Food and Drug Administration for morpholine detection in real applications. Finally, the sample recovery for GCE–EG and GCE–CNT sensors were, respectively, 107 and 103%, at 20.0 mg l–1 morpholine in the boiler water. [ABSTRACT FROM AUTHOR]

The present work describes development of a simple and selective voltammetric sensor for the simultaneous determination of three DNA bases guanine (Gua), adenine (Ade) and thymine (Thy). The proposed poly(L-arginine)-electrochemically reduced graphene oxide modified glassy carbon electrode [p(L-arg)-ERGO/GCE)] exhibited well-resolved and well-defined peaks for the electro-oxidation of these DNA bases with an enhancement in peak current and reduction in peak potential, compared to bare electrode. The electro-catalytic efficiency might be due to the synergistic electro-catalytic effect of L-arginine and reduced graphene oxide. For simultaneous determination, the peak currents of Gua, Ade and Thy showed linear variations in the concentration range 1.00 × 10–4 – 3.00 × 10–6 M, 1.00 × 10–4 – 3.00 × 10–6 M and 1.00 × 10–4 – 1.00 × 10–5 M, respectively. Mechanistic aspects of the electro-oxidation of Gua, Ade and Thy on the surface of p(L-arg)-ERGO/GCE have been explored. The proposed sensor also displayed good selectivity toward Gua, Ade and Thy without any considerable interferences from coexisting species. The applicability of the proposed sensor was demonstrated by simultaneously determining the concentration of Gua, Ade and Thy in the spiked urine and blood serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Since the beginning of the last century, there has been a high demand for renewable energy sources due to the decrease in fossil-based energy sources and the intense pollution of these energy types. Bioenergy recovery from sludge biomass is an attractive renewable energy source. Electrochemical treatment is one of the investigated physicochemical methods to increase methane production from waste activated sludge (WAS) biomass. It can be used as a new and efficient pretreatment for the hydrolysis of WAS. In this study, electrochemical technology with platinum/titanium (Pt/Ti) mesh electrodes was first applied for WAS before aerobic digestion. The effects of various operating conditions such as current intensity and initial pH of the sludge were investigated. The study showed that the amount of soluble COD of WAS increased with increasing current intensity. In addition, the results obtained showed that pH values higher or lower than the pH value of WAS (6.2) are favorable for the degradation of organic substances. An approximately 358% increase in COD solubility was detected at the end of the reaction time of 30 min at a current intensity of 25 A. The conducted study showed that electrochemical pretreatment is feasible and that increasing the methane production rate for anaerobic digester-containing wastewater treatment plants in Turkey has the potential to provide environmental and economic benefits. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Naphthalene (NAPH) and phenanthrene (PHEN) are two of the most abundant polycyclic aromatic hydrocarbons (PAHs) found in nature, and they are considered in the list of US EPA priority pollutants. The contribution of this research lies in the comprehensive analysis of a strategy for the coupling of electro-oxidation (EO) and biodegradation in a submerged membrane bioreactor (SMBR) with the objective to remove PAHs, using NAPH and PHEN as model compounds. The electrochemical degradation of NAPH and PHEN in aqueous synthetic solution has been carried out using two different anodes: Ti/IrO2 and Ti/SnO2. The effects of EO operating parameters (current density, reaction time, and pH) on the NAPH and PHEN removals were investigated applying 23 factorial design with both electrodes. Additionally, the EO effluents were analyzed for COD, NH4-N, and biodegradability (respirometry tests). The highest removals of both compounds were reached with Ti/IrO2 anode, at acidic conditions (pH of 2), current density of 50 mA cm−2, and electrolysis time of 60 min. However, the Ti/SnO2 anode allowed greater reduction of the biomass inhibition, which means that the enhancement of the EO effluent biodegradability was reached; therefore, this electrode was selected for the coupled EO–SMBR system, applying the operating conditions that improved the biodegradability of the effluent. The EO process allowed NAPH and PHEN removal efficiencies of 96 ± 5% and 94 ± 3%, respectively. The membrane bioreactor was operated with organic load of 0.6 ± 0.1 gCOD gVSS−1 d−1, hydraulic retention time of 6 h, and solid retention time of 30 d, obtaining average COD, NH4-N, NAPH, and PHEN removals of 98±0.5%, 91±6.4%, 99.1±0.96%, and 99.7±0.4% respectively. The sorption of phenanthrene onto the biomass had a low contribution, 0.9±0.2%, concluding that biodegradation was the main removal mechanism in the bioreactor. The coupled system EO–SMBR allowed high NAPH and PHEN removal efficiencies of 99.99±0.01 and 99.99±0.02%, respectively. [ABSTRACT FROM AUTHOR]

Electrode fouling is a problem that commonly occurs during electro-oxidation water purification. This study focused on identifying the fouling behavior of Pt electrode associated with the formation of polymeric layer during electro-oxidation of phenol. The in situ electrochemical measurements and non-destructive observation of the electrode morphology were reported. The results demonstrated that the electrode fouling was highly dependent on thermodynamic process of electrode that was controlled by anode potential. At anode potential lower than 1.0 V vs SHE, the direct electro-oxidation caused the electrode fouling by the formation of polymeric film. The fouling layer decreased the electrochemically active surface area from 8.38 cm2 to 1.57 cm2, indicated by the formation of polymeric film with thickness of 2.3 µm, increase in mass growing at a rate of 3.26 µg/cm/min. The degree to which the anode was fouled was independent of anion in the electrolyte. In comparison, at anode potential higher than 2.7 V vs SHE, the anions (e.g., chloride) could exert a major influence to the behavior of electrode fouling. The presence of chloride was shown to mitigate the fouling of electrode significantly through preventing the formation of polymeric film by active chlorine (e.g., Cl• and Cl2) produced from anodic oxidation of chloride. Since chloride is the most abundant anionic species existing in both natural and engineered water system, this study not only offers a deep insight into the mechanism of electrode fouling, but also suggests strategies for anti-fouling in the presence of chloride in electro-oxidation process. [ABSTRACT FROM AUTHOR]

The rapid growth in the world population and fast developing industrialization have resulted in the acceleration of environmental pollution due to inadequate treatment methods accompanied by depletion of freshwater. The current research focused on the batch treatment of slaughter house wastewater (SWW) using the sequential three-step electro-coagulation (EC)–electro-oxidation (EO)–adsorption column (AC) processes and to compare the optimized values with the Omani National Standards for the application in irrigation purpose. The characterization of SWW before and after treatment was carried out by measuring chemical oxygen demand (COD), total organic carbon (TOC), total dissolved solids (TDS), turbidity, ammoniacal nitrogen (NH4–N) and conductivity. The optimization of the treatment processes was performed by response surface methodology (RSM) using central composite design. The maximum response obtained using EC unit was 99% with an operating cost of 2.78 USD/m3. The optimum treatment conditions in EC method were found to be 4.0 pH, electrolysis time of 30 min and electrolyte dosage of 5 g/L, with a current density of 18.11 mA/cm2. The maximum reduction in COD was 97% with an operating cost 0.32 USD/m3. The optimum COD reduction in EO method was 84.5% with an operating cost of 6.87 USD/m3. The optimum process parameters in the EO process were observed at 5.0 pH, 56.22 min electrolysis time with 5 g/L electrolyte dosage and a current density of 5 mA/cm2. The response shows 56.27% reduction in COD with an operating cost of 0.088 USD/m3. The study demonstrates that both EC and EO processes for the reduction of COD have a significant effect on the current density. Using adsorption column (AC) studies, the maximum reduction in COD was 76.8% with negligible operating cost. The optimum pH in the case of AC was 7.5, with an effluent flow rate of 8.63 mL/min, and the responses were found to be 76.067%, which indicates both pH and flow rate have significant effect on the % removal of COD. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the pollutant load from tannery effluents treated by chemical coagulation (CC) followed by electro-oxidation (EO), performed in two different experimental batch-recirculated setups, one with a BDD anode and the other with Ti/Pt/PbO2 and Ti/Pt/SnO2-Sb2O4 anodes (PS). Results were compared with those obtained from EO of the raw sample. CC was performed with a Fe3+ concentration of 0.25 g L−1, and the applied current densities for EO in each setup were 60 mA cm−2 for BDD and, in the PS setup, 20 and 40 mA cm−2 for Ti/Pt/SnO2-Sb2O4 and Ti/Pt/PbO2, respectively. During CC, removals of 27% in chemical oxygen demand (COD), 14% in total nitrogen, 100% in sulfide, and 73% in Cr(VI) were observed. COD removal in the EO of the raw sample was higher than that obtained for the combined CC + EO, for both setups, showing that the organic compounds removed by CC are mainly those that would be more easily removed by EO. For most of the other parameters related with carbon and nitrogen, the removals for CC + EO were higher than for EO alone. During EO, sulfide is converted to sulfate, especially with BDD. Concerning Cr(VI) concentration, it increases during EO, in particular for PS setup. Combined treatment, with both setups, proved to be an effective choice to treat tannery effluents. [ABSTRACT FROM AUTHOR]

Tetracycline hydrochloride (TCH) electro-oxidation by commercial DSA® and commercial DSA® modified by platinum electrodeposition was evaluated. The electrodeposition was carried out at constant potential (E = − 0.73 V vs RHE) in different times (1200, 2400, and 4800 s). Scanning electron microscopy (SEM) images show that Pt electrodeposits have elongated shape particle forming a uniform surface, and energy dispersive spectroscopy (EDS) data confirms the presence of Pt on the surface. The electrochemical characterization by cyclic voltammetry showed an increase of the electrochemically active area (EAA) in function of the Pt electrodeposition time. The electro-oxidation of the TCH 0.45 mmol L−1 in H2SO4 0.1 mol L−1 solution was evaluated according to the applied current densities (j = 25, 50, 100 mA cm−2). Both the amount of platinum deposited and j showed a slight improvement in the efficiency of TCH removal, reaching 97.2% of TCH removal to DSA®/Pt4800 and 100 mA cm−2. The TCH mineralization (TOC removal), the percentage of mineralization current efficiency (MCE%), and energy consumption were 15.8%, 0.2649%, and 7.4138 kWh (g TOC)−1, respectively. The DSA®/Pt electrodes showed higher stability to TCH electro-oxidation, indicating to be a promising material for the electro-oxidation of organic pollutants. [ABSTRACT FROM AUTHOR]

Vinasse wastewater from tequila industry that has been conventionally treated is usually characterized by a chemical oxygen demand (COD) above 150 mg L−1, which is the maximum content permitted for discharge by Mexican Regulation. In order to increase the wastewater quality, different processes were applied, and from the experimental results, the advantages and limitations were analyzed. In this way, although Fenton experiments showed acceptable COD removal efficiencies (79–90%), operation as well as cost limit its adoption as a viable technology. Therefore, additional experiments explored electro-Fenton (EF) as well as adsorption coupled to EF in a tubular reactor. The corresponding data revealed that there was no additional increase in COD removal performance probably due to the low oxygen solubility in the electrolytic solution and the high pH that prevents the existence of Fe2+ ions necessary for the Fenton mixture. In view of these results, when an activated carbon (AC) filter was coupled to polarization at current densities between 0.5 and 2 mA cm−2, removal efficiencies from 71 to 81%, corresponding to final COD of 78 to 33 mg L−1, were achieved. Also, the adsorbent surface was continuously regenerated, promoting a more efficient adsorption and a longer service life for the AC filter. In this case, by using a current density of 0.5 mA cm−2, COD was reduced to sufficiently small values for discharge into natural water bodies, maintaining low energy consumption and therefore acceptable operation costs. [ABSTRACT FROM AUTHOR]

Chromium is a major strategic mineral widely used in industrial processes, yet mineral resources are decreasing, calling for advanced recycling techniques to recover chromium from ores, waste and contaminated media. Here, we review chromium resources and methods to leach out Cr, such as calcium-roasting, sodium-roasting, acidic leaching, alkaline leaching and sub-molten technology. [ABSTRACT FROM AUTHOR]

The interest in new emerging pollutants (NEPs) does not only focus on the main compounds but also the degradation or intermediate products. It is important to have an effective primary treatment for the removal/degradation of NEPs from hospital and clinical wastewater to protect the environment. In this study, nifedipine degradation was performed by an electro-oxidation method using titanium-based mixed metal oxide (MMO) electrode. The determination of nifedipine was carried out by differential pulse voltammetry at hanging mercury drop electrode using Britton–Robinson buffer (BRB). The nifedipine oxidation peak was observed at + 0.7 V at a scan rate of 20 mV s−1 in BRB pH 8. Titanium-based electrodes with different metal oxide compositions were assessed as an anode material for nifedipine degradation as follows: TiO2/Ti, IrO2–TiO2/Ti, RuO2–TiO2/Ti, and IrO2–RuO2–TiO2/Ti. The electro-oxidation of nifedipine was monitored using cyclic voltammetric techniques, and the degradation intermediates were confirmed using LC–MS. Approximately 65–83% of nifedipine degradation was achieved using RuO2–TiO2/Ti and IrO2–TiO2/Ti electrodes. Interestingly, RuO2–IrO2–TiO2 electrode showed complete (100%) electro-oxidation of nifedipine at 30 min. Two nifedipine degradation intermediates were identified, namely 5-methoxycarbonyl-2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3-carboxylic acid (compound I) and 2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarbaldehyde (compound II) during the electro-oxidation process using RuO2–IrO2–TiO2 electrode. Finally, the degradation pathway of nifedipine by MMO electrode was proposed. This is the first report on the nifedipine degradation using MMO titanium electrode by the electro-oxidation process. [ABSTRACT FROM AUTHOR]

Presented in this work is an investigation of co-deposits of Pt and Bi on Au disk (Pt-Bi/Au) toward formic acid oxidation (FAO) using voltammetry and X-ray photoelectron spectroscopy (XPS). The co-deposits of Pt and Bi on Au were prepared using an irreversible method in a mixed solution of Pt ion (1 mM) and Bi ion (5 mM), and the amount of co-deposits was controllable by the number of deposition cycles. The voltammetric studies revealed that the Pt-Bi/Au surfaces presented the characteristics of Pt, Bi, and Au depending on the number of deposition cycles. A detailed analysis of semi-quantitative results of XPS combined with hydrogen coverage on Pt and covered fraction of Au surface suggested two aspects of Pt-Bi co-deposits. One is that during co-adsorption, Bi adsorbing with a low efficiency enhanced irreversible adsorption of Pt. The other is that the Pt-Bi co-deposits would be an alloy of Pt-Bi when the Pt amount was low or Pt deposits enriched with Bi in surface regions when the Pt amount was high. The best FAO catalytic efficiency among the investigated Pt-Bi/Au surfaces was ~ 14 mA/cm2, which was higher than that of plain Pt deposits on Au (~ 6 mA/cm2) and comparable to that of sequentially prepared Bi-modified Pt deposits on Au (Bi/Pt/Au, ~ 20 mA/cm2). Because of a similarity in compositions and catalytic performances of the best Pt-Bi/Au and Bi/Pt/Au, the preparation procedure was concluded not to be critical so that the co-deposition method was more beneficial in terms of the number of deposition cycles in manufacturing electrocatalysts toward FAO. [ABSTRACT FROM AUTHOR]

The characteristics of the electrochemical oscillations that emerge along the catalytic oxidation of small organic molecules critically depend on the coverage and nature of adsorbates. Herein we report experimental results on the electro-oxidation of formic acid and methanol on platinum and platinum-modified electrodes, and under conventional, i.e., cyclic voltammetry, and oscillatory conditions. The investigation was focused on the role played by surface-free sites and the presence of a step with a short-lived specie adsorbed on electrode surface. In order to reduce the coverage of adsorbed species, and thus to increase the main reaction pathway, chronoamperometry in platinum oxide region followed by potential sweeps or the adsorption of ad atoms, like tin, to mitigate the surface poisoning was adopted. Overall, those strategies considerably improved the electrochemical oxidation of formic acid, but had no effect for methanol. Our results show that the efficiency of formic acid electro-oxidation is preferred powered, compared with methanol, on a less poisoned electrode surface, which is obtained through a self-cleaning process driven by the oscillatory electro-oxidation of organic molecules. These results are rationalized in terms of peculiarities of the reaction mechanisms of both systems. [ABSTRACT FROM AUTHOR]

Co-deposited nickel–chromium (Ni–Cr) onto the glassy carbon electrode (GCE) is successfully used as new amperometric sensor for the determination of salicylic acid (SA). SA is detected by a surface catalyzed oxidation, involving nickel(III) oxyhydroxides in alkaline solution. The performance of the biosensor Ni–Cr/GCE is characterized by cyclic voltammetry, chrono-amperometry, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). The electrochemical behavior of the Ni–Cr alloy is qualitatively similar to that of pure nickel electrode. However, it is proposed that a higher degree of disorder of the oxyhydroxide layer structure is present on the top of the alloy. The electroactivity of Ni–Cr/GCE is studied as a function of the molar fraction (Xf%) of Cr3+ in the deposition bath. The results show that Ni–Cr/GCE exhibits a high electrocatalytic activity for SA oxidation. The Ni–Cr/GCE with 28Xf% Cr3+displays the best activity with a high response signal, a good sensitivity of 71.22 μA mM–1, a low detection limit of 0.1 μM (S/N = 3) and a fast response time (<3 s). Moreover, the reproducibility, selectivity and applicability of this electrochemical sensor are satisfactory evaluated. [ABSTRACT FROM AUTHOR]

Synthetic solutions of 2-chlorophenol (2-CP, 1 mM) were treated in an undivided continuous flow electrochemical reactor equipped with boron-doped diamond (BDD) electrodes. The process was conducted at different current densities (j = 0.10, 0.125, and 0.14 A cm−2), initial pH (4.0, 7.3, and 9.0), and volumetric flow rate (Q = 0.5, 1.0, and 1.5 L min−1). The results of this study showed that the best operational conditions were: j = 0.14 A cm−2, pH = 7.3, and y Q = 1 L min−1. Under these operational conditions the degradation and mineralization of 2-CP were, 100% and 96%, respectively, after 6 h of electrolysis time. The by-products were identified by UHPLC. Also, it was found that the electrochemical degradation of 2-chlorophenol follows a pseudo-first order kinetics. Furthermore, these results demonstrate that the electrolysis process employed in this work allows high percentages (96%) of mineralization of 2-CP, a relative low treatment cost ($ 3 MXN/ 2.5 L of synthetic solution), and that the process is applicable to remediate wastewater. [ABSTRACT FROM AUTHOR]

This study deals with disintegration of biological sludge by electro-oxidation process for the purpose of improving anaerobic biodegradability of sludge. A pair of titanium (Ti) electrode and a pair of titanium electrodes coated with RuO2 (Ti/RuO2) used for both anode and cathode and their effects on anaerobic sludge bio-processing were investigated. Process conditions were optimized by response surface methodology. Disintegration degree (DD) parameter was used as system response. Optimum conditions were found to be 20 V for 30 min for both electrode couples. DD = 13.9% was achieved for Ti electrodes application, addition of supporting electrolyte (10 g/L Na2SO4) improved disintegration the performance of sludge (DD = 17.3%). Ti/RuO2 electrodes provided higher DD values and the highest DD were determined as 16.6% and 10 g/L Na2SO4 supporting electrolyte addition increased the DD value to 20.4%. Biochemical methane potential (BMP) test results suggest that electro-oxidation enhanced the anaerobic biodegradability of sludge. Electro-oxidation with Ti/RuO2 electrodes allowed more methane gas formation in BMP test. Disintegrated sludge with the pair of Ti and Ti/RuO2 electrodes provided 11.8% and 34.1% higher methane production comparing to the raw sludge at the end of the 40 days of incubation, respectively. [ABSTRACT FROM AUTHOR]

The 3D flower-like Ni0.6Zn0.4O microspheres were prepared by calcination treatment of Ni–Zn LDHs (layered double hydroxides) that were obtained through a hydrothermal method. The yielded Ni0.6Zn0.4O microspheres were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The results showed that the calcinated microspheres of Ni0.6Zn0.4O still well maintained the flower-like architecture of Ni–Zn LDHs. The surface area, total pore volume, and average pore diameter of the Ni0.6Zn0.4O microspheres were obtained with the values of 36.106 m2 g−1, 0.111 cm3 g−1, and 5.676 nm, respectively. As modified anode active materials, the Ni0.6Zn0.4O microspheres exhibited excellent electrocatalytic performance and fast electrochemical kinetics for methanol oxidation in strong alkaline electrolyte where the high surface area of flower-like Ni0.6Zn0.4O microspheres provides the high contact probability between catalysts and reactants. The presence of Zn also improves the electron transfer within catalysts inside. Also, the Ni0.6Zn0.4O modified electrode maintained good electrocatalytic performance during the term of 36,000 s. [ABSTRACT FROM AUTHOR]

Pd, PdSn, PdBi and PdBiSn nanostructured thin films were prepared on Au substrate using the electrochemical atomic layer deposition technique. The activity of the nanostructured thin films towards the electro-oxidation of ethanol was tested in alkaline media using electrochemical methods. Scanning electron microscopy results showed that the nanoparticles were evenly distributed on the surface, while the elemental analysis confirmed the presence of all elements on the prepared materials. Cyclic voltammetry studies revealed that the addition of Sn and Bi on Pd improved the activity of Pd and that the ternary nanostructured catalyst was more active towards the oxidation of ethanol than the binary catalysts. [ABSTRACT FROM AUTHOR]

The reaction of electrochemically produced o-benzoquinone from oxidation of catechol as Michael acceptor with L-lysine as nucleophiles has been studied in aqueous solution with various pH values, different electrodes and different concentration of L-lysine using cyclic voltammetry, controlled potential coulometry and differential pulse voltammetry. The participation of reaction of o-benzoquinone with L-lysine at higher concentration of nucleophiles in the second scan of potential was observed. The products generated from the reaction are assumed to be 2-amino-6-((3,4-dihydroxyphenyl)amino)hexanoic acid that undergo electron transfer at more negative potentials than the catechol. The effect of pH of catechol in presence of L-lysine was studied by varying pH from 5 to 11. The reaction was strongly influenced by the pH as well as concentration of L-lysine. The reaction was mostly favorable in 2 mM of catechol and 70 mM of L-lysine at pH 7. The behavior of the reaction mechanism was of electron transfer, chemical reaction and electron transfer (ECE) type. [ABSTRACT FROM AUTHOR]

Rational hydrophobic anode has been considered as a promising approach for water pollution remediation. However, the construction method of the hydrophobic electrode is limited, such as adding hydrophobic polymer materials. Herein, we address this limitation by developing Ce-modified Ti-PbO2 electrodes with distinctive micro/nanostructures and surface hydrophobicity by the typical electro-deposition process. The Pb ions in the lattice of PbO2 crystals can be substituted by cerium ions and the PbO2 crystal grains were refined when the concentration of cerium ions is low. Specifically, as further increase of the cerium content in plating solution, the CeO2 gradually precipitated on the surface of PbO2 and the PbO2 phase was becoming more and more amorphous. Namely, the pyramid structure converted to surface outshoots with outward oriented-growth, and then evolved gradually to branched projections, until the coral-like architecture was constructed by assembling of small particles. More importantly, the micro/nanostructures and surface hydrophobic PbO2 coatings can significantly enhance generating and utilizing efficiency of hydroxyl radicals, charge transfer rate, and electrochemical active area. The excellent electrochemical performance is mainly attributed to superior catalytic activity arises from synergetic effects between cerium and PbO2 and distinctive micro/nanostructures hydrophobicity surface of Ce-modified Ti-PbO2 electrodes.Graphical abstractA novel Ce-modified Ti-PbO2 electrode with distinctive micro/nanostructures and surface hydrophobicity was fabricated by the typical electro-deposition process. The as-prepared Ce-modified Ti-PbO2 electrode possesses high generating and utilizing efficiency of hydroxyl radicals, fast charge transfer, and large electrochemical active area due to its higher OEP, lower charge transfer resistance, higher carrier density (ND value), and stronger surface hydrophobicity. Consequently, the Ce-modified Ti-PbO2 electrode exhibited better electro-oxidation performance for removing reactive brilliant blue KN-R, as compared with that of Ti-PbO2-reference (without Ce modifying). [ABSTRACT FROM AUTHOR]

Abstract: Wastewater from sugar industry has multiple combinations of organic and inorganic contaminants. It has an adverse impact on nearby environment and requires specific type of treatment to minimize the effect. To treat the sugar industry wastewater, an attempt has been made with the electrochemical process by using aluminum electrode. Four process parameters were selected, namely initial pH (pH 4-10), current density (44.5-133.5 A/m2), electrode spacing (10-20 mm), and experimental time (20-100 min) to optimize the condition with surface response methodology. At optimum condition maximum, 69.2% chemical oxygen demand and 88.6% color reduction were archived at pH 7, current 1 A, electrode distance 1.5 cm and treatment time 60 min. The coefficient of the model predicted (R2) value of 0.87 and 0.48, and adjusted (R2) value of 0.64 and 0.45 for chemical oxygen demand and color reduction were obtained. The physicochemical characteristic indicates that settling sludge has more inorganic material as compared to floating sludge; hence, settling sludge has low calorific value than floating sludge.Graphical Abstract: [ABSTRACT FROM AUTHOR]

This paper provides an overview of recent advances in urea electro-oxidation. Urea sources are abundant from human urine, urea-containing wastewater, and industrial urea, thus becoming an attractive option as anodic fuel for the application in direct urea fuel cells (DUFCs). Besides, as a hydrogen-rich chemical fuel, urea can also be electrolyzed to produce hydrogen for energy storage in the near future. The exact mechanisms of urea decomposition are pretty different in alkaline or neutral mediums and are separately discussed in detail. More importantly, the development of anodic electro-catalysts is of great significance for improving the electrochemical performance of both DUFCs and urea electrolysis cells, which is systematically summarized in our review. Challenges and prospects on the future development of urea electro-oxidation are particularly proposed. [ABSTRACT FROM AUTHOR]

Aiming to further promote the performance of PdNi for formic acid electro-oxidation (FAEO), ternary Pd-Ni-Ir/C nanocatalyst was synthesized via an ethylene glycol-assisted NaBH4 reduction process. The physical characterizations show that the PdNiIr nanoparticles with a small mean size are well dispersed on carbon support. The electrochemical measurements demonstrate that the PdNiIr/C catalyst exhibits the highest activity for FAEO. The onset and peak potential of FAEO on PdNiIr/C is about 70 mV more negative than that on the Pd/C and PdNi/C catalysts. The mass activity of Pd in PdNiIr/C at 0.14 V is 2830 mA mg−1Pd, which is about 1.65, 1.82, and 2.2 times as high as that of PdIr/C, PdNi/C, and Pd/C, respectively. The enhancement should be attributed to the electronic effect and bi-functional mechanism. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation of four different alcohol molecules (methanol, ethanol, n-butanol and 2-butanol) at electrodeposited Pt film and carbon-supported Pt catalyst film electrodes, as well as the effect of mass transport on the oxidation reaction, has been studied systematically using the rotating disk electrode (RDE) technique. It was shown that oxidation current decreased with an increase in the rotation rate (ω) for all alcohols studied over electrodeposited Pt film electrodes. In contrast, the oxidation current was found to increase with an increase in the ω for Pt/C in ethanol and n-butanol-containing solutions. The decrease was found to be nearly reversible for ethanol and n-butanol at the electrodeposited Pt film electrode ruling out the possibility of intermediate COads poisoning being the sole cause of the decrease and was attributed to the formation of soluble intermediate species which diffuse away from the electrode at higher ω. In contrast, an increase in the current with an increase in ω for the carbon supported catalyst may suggest that the increase in residence time of the soluble species within the catalyst layer, results in further oxidation of these species. Furthermore, the reversibility of the peak current on decreasing the ω could indicate that the surface state has not significantly changed due to the sluggish reaction kinetics of ethanol and n-butanol. [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) are considered a viable alternative power source for both stationary and mobile applications. Obstacles to widespread use of DEFCs include the slow electro-oxidation kinetics of ethanol, which has been countered by employing combinations of noble metals and organic compounds as catalysts, e.g., a platinum alloy and perylene-3,4:9,10-tetracarboxylic acid derivatives (PDIs). This study investigates the performance of a PDI functionalized with 4-amino pyridine (PDI1) and subsequently dispersed in Pt/C (Pt/C/PDI1) and PtSn/C (PtSn/C/PDI1). The performance of these catalysts in ethanol electro-oxidation (EOR) was compared to that of metallic catalysts (PtSn/C and Pt/C). The forward potential scan indicated that the peak current densities (j) on the catalysts Pt/C/PDI1 and PtSn/C/PDI1 were ~ 1.7 and ~ 1.3-fold that of Pt/C and ~ 1.8 and ~ 1.4-fold that of PtSn/C. Concerning ethanol oxidation, this indicates that Pt/C/PDI1 and PtSn/C/PDI1 exhibit better catalytic activity in EOR than Pt/C and PtSn/C do. [ABSTRACT FROM AUTHOR]

In this work, the electrochemical oxidation of catechols 1a and 1b was studied in the presence of pyrazolidine-3,5-dione ( 3a), as a nucleophile, in a mixture of ethanol and a phosphate buffer solution (0.1 M, pH 7), as a green medium, using the cyclic voltammetry and controlled-potential coulometry techniques. The results obtained indicated that the oxidized forms of these catechols ( 2a and 2b) participated in the Michael addition reactions with pyrazolidine-3,5-dione ( 3a), and converted, via an ECEC mechanism, to their corresponding benzofurans ( 7a and 7b). In this work, some new benzofuran derivatives were synthesized with good yields and high purities using a facile, one-pot, and environmentally friendly electrochemical method in the absence of any chemical catalyst, toxic solvent, and hard conditions. [ABSTRACT FROM AUTHOR]

In the present work, a novel WO-gCN/Pt-Sn-Os catalyst was synthesized and used for fabrication of a modified electrode for electro-oxidation of methanol molecules. The WO-gCN nanocomposite was transferred onto the surface of a glassy carbon electrode (GCE) and then, the surface of the modified electrode was potentiostatically coated with Pt-Sn-Os ternary alloy nanoparticles. The morphology of the prepared electrode (GCE/WO-gCN/Pt-Sn-Os), was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The electro-oxidation of methanol molecules on the surface of GC/WO-gCN/Pt-Sn-Os modified electrode was studied using various electrochemical methods such as cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The charge transfer resistance and the double layer capacitance were determined by the EIS measurements. The electro-oxidation of methanol molecules was also investigated from kinetic point of view using the proposed modified electrode. The electrocatalytic performance of the modified electrode was also compared with the other constructed electrodes for methanol oxidation. [ABSTRACT FROM AUTHOR]

Background: Annually, large quantities of dyes are produced and consumed in different industries. The discharge of highly colored textile effluents to the aquatic environments causes serious health problems in living organisms. This paper investigates the performance of each of the electro-oxidation and electro-reduction pathways in the removal of reactive red 120 (RR120) from synthetic textile effluents using a novel electrochemical reactor. Methods: In the current study, a two-compartment reactor divided by cellulosic separator was applied in batch mode using graphite anodes and stainless steel cathodes. Central Composite Design was used to design the experiments and find the optimal conditions. The operational parameters were initial dye concentration (100-500 mg L-1), sodium chloride concentration (2500-12,500 mg L-1), electrolysis time (7.5-37.5 min), and current intensity (0.06-0.3 A). Results: The results showed that electro-oxidation was much more efficient than electro-reduction in the removal of RR120. According to the developed models, current intensity was the most effective factor on the electro-oxidation of RR120 as well as in power consumption (Coefficients of 12.06 and 0.73, respectively). With regard to the dye removal through electro-reduction, electrolysis time (coefficient of 8.05) was the most influential factor. Under optimal conditions (RR120 = 200 mg.L-1, NaCl = 7914.29 mg.L-1, current intensity = 0.12 A, and reaction time = 30 min), the dye was removed as 99.44 and 32.38% via electro-oxidation and electro-reduction mechanisms, respectively, with consuming only 1.21 kwhm-3 of electrical energy. Conclusions: According to the results, electro-oxidation using graphite anodes in a cell divided by cellulosic separator is very efficient, compared to electro-reduction, in the removal of RR120 from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this study, central composite design at five levels (− β, −1, 0, +1, + β) combined with response surface methodology has been applied to optimize C.I. Reactive Yellow 186 using electro-oxidation process with graphite electrodes in a batch reactor. The variables considered were the pH ( X ), NaCl concentration (M) ( X ), and electrolysis time (min) ( X ) on C.I. Reactive Yellow 186 were studied. A second-order empirical relationship between the response and independent variables was derived. Analysis of variance showed a high coefficient of determination value ( R = 0.9556 and 0.9416 for color and COD, respectively). The optimized condition of the electro-oxidation of Reactive Yellow 186 is as follows: pH 3.9; NaCl concentration 0.11 M; and electrolysis time 18 min. Under this condition, the maximal decolorization efficiency of 99 % and COD removal 73 % was achieved. Detailed physico-chemical analysis of electrode and residues of the electro-oxidation process has also been carried out UV-Visible and Fourier transform infrared spectroscopy. The intermediate compounds formed during the oxidation were identified using a gas chromatography coupled with mass spectrometry. According to these results, response surface methodology could be useful for reducing the time to treat effluent wastewater. [ABSTRACT FROM AUTHOR]

Conducting polymer nanostructuring enables a substantial improvement of many electro-catalytic processes, e.g., formic acid (HCOOH, FA) electro-oxidation. In this case, a stainless steel (SS) electrode is first modified with poly(1-amino-9,10-anthraquinone- co- o-phenylenediamine) (COP) and then, by means of a template that can be chemically removed, poly(1-amino-9,10-anthraquinone) nanowires (P1AAQnw) are electro-synthesized; this procedure has allowed the effective FA electro-catalytic oxidation generating adsorbed CO, which is quickly converted to CO. Subsequently, when platinum nanoparticles (dispersed by electro-chemical techniques) are also incorporated on the polymeric nanowires, oxidation peaks are observed at ca. 1000 mV, with a current increase up to fourfold. In this way, the method provides a highly reproducible nanostructured electrode that is prepared solely by electro-chemical techniques offering promising results for FA electro-catalytic oxidation. [ABSTRACT FROM AUTHOR]