关键词： Sodium hydroxide  

摘要： This paper reports the comparison of the electrochemical properties of 3D PLA-graphene electrodes (PLA-G) under different activation conditions and through different processes. In this work, the performance of the electrodes was evaluated after polishing, electrochemical and chemical treatments and a combination of them. The best results were obtained with hydroxide activation using 1.0 mol L-1 NaOH for 30 min of immersion, which promoted the saponification of PLA exposing the graphene nanoribbon structures. The improvement was more evident also after electrochemical activation, which led to a great increase in surface area, defects, electron transfer rate and amount of edge sites. The analytical performance of the proposed PLA-G(NaOH-30-EC) electrode was evaluated in the presence of dopamine (DA) by three electrochemical techniques, presenting a broad linear range, and limits of detection of 3.49, 2.17 and 1.67 mu mol L-1 were obtained by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), respectively. The separation and quantification of DA in the presence of AA and UA was also reported. The sensor showed good repeatability and reproducibility and was successfully applied to DA determination in synthetic urine and human serum, showing good recovery, from 88.8 to 98.4%. Therefore, the activation methods were essential for the improvement in the 3D PLA-G electrode properties, allowing graphene surface alteration and electrochemical enhancement in the sensing of molecular targets.

关键词： Heterogeneous electro-Fenton   Heterogeneous Fenton   Mineral catalyst   Heterogeneous photoelectro-Fenton   Ponceau SS   Water treatment  

摘要： Modified sodium vermiculite, an iron-rich clay mineral, has been used in novel heterogeneous electro-chemical Fenton-based treatments, so-called electro-Fenton (EF)-vermiculite, UVA photoelectro-Fenton (PEF)-vermiculite and solar photoelectro-Fenton (SPEF)-vermiculite. Tests were made with 130 mL of 0.150 mM Ponceau SS diazo dye in 0.050 M Na2SO4 at pH 3.0, in the presence of 1.0 g L-1 catalyst microparticles. The electrolyses were performed in an undivided cell with a boron-doped diamond anode (BDD) and air-diffusion cathode for H2O2 production, at 33.3 mA cm(-2). Decolorization and mineralization were upgraded in the sequence: EF-vermiculite < PEF-vermiculite < SPEF-vermiculite. The removal of organics occurred by the combined action of center dot OH oxidant formed at the BDD surface and homogeneous and heterogeneous Fenton's reactions, along with the photolysis caused by UVA light or sunlight. The homogeneous Fenton's reaction resulted from iron ions leaching, but the heterogeneous mechanism was prevalent. Comparative treatments by anodic oxidation in the presence of H2O2 and homogeneous EF were less effective than EF-vermiculite. The diazo dye absorbance decays agreed with a pseudo-firstorder kinetics. SPEF-vermiculite was the most powerful process, yielding total decolorization and 84.1% mineralization after 300 and 360 min, respectively. The influence of catalyst concentration, current density and diazo dye content on PEF-vermiculite performance was examined. Oxalic, oxamic, malic, tartronic and acetic acids were detected as final short-linear carboxylic acids. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Oxidation  

摘要： The effect of process parameters on the electrochemical performance of a glutamate (Glu) microbiosensor was studied. Glu is a major excitatory neurochemical that is essential for regulation of several brain functions. Glu dysregulation is associated with several neuropathological conditions such as epilepsy, Parkinson's and Alzheimer's disease. Here, an enzymatic microbiosensor in the form of a ceramic-shank substrate enabled platinum (Pt) microelectrode array (MEA) was employed to investigate the effect of key process parameters such as MEA surface cleaning methods, the effects of GluOx concentration, GluOx loading and size-exclusion layer thicknesses on Glu sensitivity and selectivity towards common interferents. A two-step cleaning procedure demonstrated a 57.4% increase in hydrogen peroxide sensitivity, which is due to 80-fold and 2-fold reductions respectively in the charge transfer resistances of the Pt microelectrode grains and grain boundaries. The microbiosensor demonstrated an excellent combination of sensitivity (530 +/- 34 nA cm(-2)mu M-1), selectivity (841 +/- 54) and long-term stability (2 months). These results provide a detailed account of changes in electrochemical properties and sensitivities of Pt microelectrodes toward peroxide, the rationale for choosing a higher GluOx concentration (0.4 U/mu l) instead of 0.1 U/mu l, which is the most commonly used concentration in the literature and recommendations on the enzyme loading and placement of size-exclusion coatings and their deposition conditions, which significantly affects the biosensor performance. (c) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

关键词： Electrochemical impedance spectroscopy  

摘要： Electrochemical impedance spectroscopy (EIS) is an experimental technique that is frequently used in electrochemistry. While measuring EIS spectra is relatively simple, the interpretation of the data is hindered if the electrochemical system under study is not linear, causal, stable, and time-invariant. These requirements can be assessed by applying the Kramers-Kronig relations or Hilbert transform (HT) to the EIS data. Here, we develop a new probabilistic approach to compute the HT of impedance spectra. The method, called the Gaussian process Hilbert transform (GP-HT), leverages Gaussian processes that are constrained to comply with the HT. The GP-HT, which is an infinite-dimensional generalization of previously developed Bayesian HT, is used to predict the credible intervals of the real part of the EIS spectrum from its imaginary component. The quality of the measurements can then be assessed by benchmarking the prediction against the real part of the experimental EIS spectrum. It is foreseen that, as a new approach for calculating the HT, the GP-HT will stimulate more research on the probabilistic interpretation of the EIS and its consistency.

关键词： BiVO4   Doping   Heterojunction   Molybdenum   Photoconversion   Water oxidation  

摘要： Metal-doping is widely used to enhance charge generation and reduce carrier recombination of BiVO4 for catalyzing water oxidation. In this work, different Mo-doping levels are applied to synthesize Mo-doped BiVO4 (MBVO) on conductive glasses. Molybdenum plays multiple roles of dopant, structure-confined mediator, and sources for forming additional semiconductor. The MBVO with lower Mo-doping levels presents bi-layered structure with nanowire overlayer and nanorod underlayer, which can develop facile one-dimensional charge-transfer paths and efficient heterojunction. With preferable design of nanowire and nanorod layers, the high light absorption, small charge-transfer resistance and high carrier density are attained for MBVO with 1% Mo-doping, which shows the highest photocurrent density of 2.5 mA/cm(2) at 1.23 V-RHE, smallest onset potential of 0.22 V-RHE and highest maximum photoconversion efficiency of 2.20%. This work carefully illustrates the function of molybdenum and firstly constructs the unique bi-layered structure for MBVO to display outstanding photoelectrochemical performance for catalyzing water oxidation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Sugar beet wastewater   Electrooxidation   Electrochemical peroxidation   Response surface methodology   Reaction rate constant  

摘要： Sugar production is a water intensive process that produces a large amount of wastewaters with high concentration of chemical oxygen demand (COD), mostly consists of organic carbon compounds. Conventional treatment methods are limited to provide the necessary treatment of effluent COD to meet the regulatory limits prior to discharge. The treatment performance of electro-oxidation (EO) and electrochemical peroxidation (ECP) for organic removal were investigated in a laboratory scale study. The experimental conditions were optimized for both EO and ECP using Box-Behnken Design (BBD) and the models provided highly significant quadratic models for both treatment methods. The effects of pH, H2O2 dosage, current density, and operation time were investigated using BBD. The results showed that EO could remove 75% of organics at optimum conditions of pH 5.3;current density of 48.5 mA cm(-2);and operation time of 393 min. The predicted values were in reasonable agreement with measured values. ECP could remove total and soluble COD and total and dissolved organic carbon by 65, 64, 66, and 63%, respectively at optimum conditions of H2O2 dosage of 21 mL L-1;current density of 48 mA cm(-2);and operation time of 361 min. The methods were compared based on removal efficiency and energy consumption during operation. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Zinc oxide  

摘要： O-Polar ZnO(0001) single crystals and ZnO and Mg-doped ZnO (MgZnO) films which were subsequently deposited on the ZnO crystals by a pulsed laser deposition (PLD) method were electrochemically investigated through the interfaces with ionic liquid (IL) in a vacuum. The sample surfaces were confirmed to be atomically clean and flat by reflection high energy electron diffraction (RHEED) observation, prior to their electrochemical measurements. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were then performed, and the donor density, flat band potential of these ZnO samples, and the electric double layer capacitance at the IL/ZnO interfaces were successfully evaluated. The flat band potentials of ZnO and MgZnO films were found to shift to more negative potentials relative to those of the single crystal ZnO, with different values for thicker films, respectively. Some possible origins of the different flat band potentials between ZnO and MgZnO films, and their film thickness dependence of the flat band potential will be discussed in this paper.

关键词： Electro-oxidation   Urea   Mixed metal oxide   Energy consumed   Box-Behnken design   Optimization  

摘要： The present study investigates the electro-oxidation (EO) treatment of urea containing wastewater using mixed metal oxide (MMO) anodes. Box-Behnken design (BBD) was employed to analyze the effects of various operational process parameters like current density (j), NaCl dose (n), treatment time (t) and pH in an EO reactor in batch mode. The performance of the treatment process was evaluated in terms of % degradation and energy consumption. Under optimum conditions, the experimental results showed that more than 94.78% of degradation of urea was achieved. Electro-oxidation has effectively reduced the TOC (90%) under optimum conditions. Attempts were made to integrate the two process electro-oxidation and photocatalysis i.e. Photoelectrocatalysis within the same treatment unit for the enhanced degradation of target pollutant. The electro-oxidation process with mixed metal oxide anode has also attained a significant removal of nitrogen by transforming into the NO3- and NH4+ through the formation of OH center dot and reactive chlorine species. Characterization techniques like SEM-EDX and XRD have confirmed the durability of mixed metal oxide anodes even after 90 recycles of the experimental run. The total operating cost for electro-oxidation treatment of urea under optimized conditions is found to be 0.78 $/m(3). (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

摘要： INTRODUCTION Fluoride in drinking water is an inorganic anion and is among the most important elements for human health.1-3 The World Health Organization (WHO) guideline for the upper limit of fluoride in drinking water is between 1-1.5 mg.L-1.4 Excessive amounts result in various diseases such as dental and skeletal fluorosis, endocrine disruption, reproductive decline, immunopathy, decreasing intelligence quotient (IQ), and effects on hypertension as well as birth height and weight.5-11 Fluoride is found in the wastes and air from various industrial activities, especially electroplating, and the production of semiconductors, glass, steel, ceramics, and chemical fertilizers.1216 In Iran, the fluoride concentration in several areas is higher than 1.5 mg.L-1.17,18 Various methods are used to reduce the fluoride level in water.19-28 The electrochemical method has many advantages such as low operating cost, the capability of being used for a wide range of organic and inorganic pollutants, less contact time, and higher charged flocks entering the stilling basin.29 As a result of the health risks of high fluoride concentrations in drinking water and the mentioned benefits of the electrochemical process, the current study aimed to investigate the application of electrochemical processes to fluoride removal from artificially polluted water. According to the multiple linear regression model, to remove fluoride by the electrochemical process, the main effective factor on removing fluoride is the amount of electrical energy (P<0.001) while the initial concentration of fluoride has less effect on the removal efficacy (P=0.184). (ProQuest: ... denotes formula omitted.) Where: R = Fluoride removal efficiency E = electrical energy (kWh) Fjnjtjai = initial fluoride concentration (mg/L) CONCLUSION This research investigated the performance of the electrochemical process with aluminum electrodes, for fluoride removal from polluted water. At these current densities, the initial fl

关键词： Electro-oxidation process   Adsorption treatment   Ciprofloxacin   Caenorhabditis elegans   Detoxification   Environmental water  

摘要： Pharmaceutical-based contaminants are the major reasons for morbidity and mortality in aquatic animals and lead to several side effects and diseases in human community. Availability of proper, efficient, and cost-effective treatment technologies is still scarce. In this study, an efficient combined treatment technique (electrochemical oxidation and adsorption processes) was developed for the complete detoxification of most commonly used antibiotic, ciprofloxacin in aqueous solution. Electrochemical degradation of ciprofloxacin was performed using titanium-based tri-metal oxide mesh type anode, and the effective oxidative potential, electrolysis time, and pH for the degradation of ciprofloxacin were thoroughly evaluated. Sulfate, fluoride ions and toxic byproducts generated during electrochemical oxidation of ciprofloxacin were subsequently removed through a simple adsorption treatment using activated charcoal for 90 min. Further, the toxicity of the treated water was assessed with the nematode Caenorhabditis elegans species at different time intervals by observing the expressions of important stress-responsive genes viz., sod-3, hsp-16.2, ctl-1,2,3 and gst-4. The results exhibited that the combined process of electrochemical oxidation and adsorption treatment is simple, low-cost as well as effective to eliminate ciprofloxacin and its toxic byproducts in aqueous solution.