Electrochemical Oxidation Behavior Research Articles

Development of a glycine-MWCNT nanohybrid via electropolymerization for enhanced electrochemical detection of diclofenac

In this study, electropolymerization of glycine (Gly) was carried out to enhance the sensitivity of the carbon paste electrode (CPE) blended with multi-walled carbon nanotubes (MWCNTs) for electroanalysis of diclofenac (DCF). Analytical applications and electrochemical performance were examined using various voltammetric methods, including differential pulse voltammetry and cyclic voltammetry. Atomic force, scanning electron microscopy, dispersive X-ray, X-ray diffraction, and Raman spectroscopy were used to ascertain the surface topology of the modifier. The modified sensor with high electrocatalytic properties could electrochemically oxidize DCF, resulting in an enhanced current compared to the bare CPE when an anodic peak was detected at 0.77 V peak potential for the bare CPE, consisting of 0.1 mM DCF and 2.11 µA peaks current. The working electrode CPE was then modified with MWCNT and glycine. For MWCNT/CPE, a peak was seen at 5.20 µA and 0.75 V, and a more intense peak was observed for poly(Gly)-MWCNT/CPE at 11.52 µA and 0.74 V. The poly(Gly)-MWCNT/CPE exhibited a five-fold enhancement of peak current compared to bare CPE. The modified electrode displayed fast electron transfer, reproducibility, and repeatability. The study explored how factors like immersion time, pH variation, scan speed, and substance concentration could influence the peak current of DCF. Methods such as differential pulse voltammetry and cyclic voltammetry were utilized to examine the electrochemical oxidation behavior of DCF. The concentration variation is 0.5 µM to 7.0 µM, and the detection limit was 7.96 × 10-8 M. The rate constant (ks) for the electrochemical process was 1.710 s-1. The DCF of pharmacological and biological test substances was measured using the constructed modified electrode.

Oxidation stability of N-ethyl-2-pyrrolidinone under high voltage environments

This work was aimed at investigating the electrochemical oxidation behavior of poly(vinylpyrrolidone) (PVP, a popular dispersant in the process of battery production) under high voltage environments. N-ethyl-2-pyrrolidone (NEP) was selected as a compound representative of PVP. Working electrodes were designed and prepared with a mixture of NEP and ethylene vinyl alcohol (EVOH) as a vehicle, and conductive carbon black as the electron transport material. Linear sweep voltammetry (LSV) was used to monitor the reactions underwent by NEP. The oxidative products were analyzed with X-ray photoelectron spectroscopy (XPS) and gas chromatography coupled with mass spectrometry (GC–MS). LSV revealed electrochemical oxidation of NEP taking place at voltages higher than 4 V. XPS and GC–MS revealed that the electrochemical oxidative products contained an ammonium group derived from the loss of electrons of the NEP under the electric field. Two types of ammonium species were identified: (i) species resulting from the loss of four electrons followed by hydrolysis and; (ii) species of higher molecular weight as a result of the replacement of ethyl group on NEP with methoxy (from lithium methoxide) followed by loss of protons and electrons (two-electron-two-proton process) with hydrogen being exchanged with fluorine. A reasonable mechanism was proposed to explain these results.

Dual-structured oxide coatings with enhanced wear and corrosion resistance prepared by plasma electrolytic oxidation on Ti-Nb-Ta-Zr-Hf high-entropy alloy

The electrochemical oxidation behavior of high-entropy alloys (HEAs) is supposed to be different from that of traditional Ti-based alloys due to the presence of multi-principal elements. In this work, equi-atomic Ti-Nb-Ta-Zr-Hf bio-HEA (PEO-free) was subjected to plasma electrolytic oxidation (PEO) at 150 (PEO-150 V), 200 (PEO-200 V) or 250 V (PEO-250 V). Due to substrate oxidation, the PEO-formed coatings were composed of multiple metallic oxides in their complete oxidation states. Moreover, elements such as Ca, Si, Na and O from the electrolyte were also introduced into the coatings. Different from the amorphous nature PEO-150 V coating, the microstructures of PEO-200 V and PEO-250 V coating were characterized by Hf0.5Zr0.5O2 nano-crystals homogeneously dispersed in amorphous coating matrices, with PEO-250 V group (∼20 μm in diameter) possessing larger nano-crystals than PEO-200 V group (∼6 μm in diameter). The dry-sliding test identified an order of PEO-200 V > PEO-250 V > PEO-150 V > PEO-free group for the wear resistance. The corrosion resistance evaluated by electrochemical impedance spectroscopy followed the trend of PEO-150 V > PEO-200 V > PEO-250 V > PEO-free group. The in vitro experiments confirmed the favorable cyto-compatibility of PEO-treated surfaces. Together, the results indicate that the coating with appropriate amorphous/crystalline dual-structure on Ti-Nb-Ta-Zr-Hf bio-HEA surface is promising for biomedical applications.

Zinc Oxide–Graphene Nanocomposite-Based Sensor for the Electrochemical Determination of Cetirizine

A nanocomposite electrode of graphene (Gr) and zinc oxide (ZnO) nanoparticles was fabricated to study the electrochemical oxidation behavior of an anti-inflammatory drug, i.e., cetirizine (CET). The voltametric response of CET for bare CPE, Gr/CPE, ZnO/CPE, and the ZnO-Gr nanocomposite electrode was studied. The modifier materials were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray powder diffraction (XRD) to comprehend the surface morphology of the utilized modifiers. The influence of pH, scan rate, and accumulation time on the electrooxidation of CET was examined. It was found that the electrochemical oxidation of CET was diffusion-controlled, in which two protons and two electrons participated. The detection limit was found to be 2.8 × 10−8 M in a linearity range of 0.05–4.0 µM. Study of excipients was also performed, and it was found that they had negligible interference with the peak potential of CET. The validation and utility of the fabricated nanocomposite sensor material were examined by analyzing clinical and biological samples. Stability testing of the nanocomposite electrode was conducted to assess the reproducibility, determining that the developed biosensor has good stability and high efficiency in producing reproducible results.

Cream production and biological in vivo/in vitro activity assessment of a novel boron-based compound derived from quercetin and phenyl boronic acid

Boronic acids constitute an important class of synthetic intermediates due to their high chemical stability, ease of use, moderate organic Lewis acid properties, reduced reactivity profiles and numerous biological activities such as antibacterial and antioxidant. The present study documents the synthesis and characterization of a novel boronic ester compound (3,5,7-trihydroxy-2- (2-phenyl benzo [d] [1,3,2] dioxaborol-5-yl) −4H-chromen-4-a) which was derived from phenyl boronic acid and quercetin. The new boron-based compound was used in the cream formulation after evaluating its antioxidant, antibacterial, anti-enzyme, anticancer activities and electrochemical oxidation behaviour. Furthermore, the cream has been dermatologically and microbiologically tested. Also, histological evaluation of the agent was estimated on multiple rat organs by hematoxylin-eosin staining method. Antioxidant potential of the new compound was tested by ABTS cation radical (IC50: 0.11 ± 0.01 µg/mL), DPPH free radical scavenging (IC50: 0.14 ± 0.01 µg/mL), and CUPRAC (A0.5: 1.73 ± 0.16 µg/mL) methods, respectively. The compound determined to have a dominant antioxidant activity. In addition, the synthesized compound had no toxic effect on the healthy cell line (PDF), while having a very high (IC50: 18.76 ± 0.62 µg/mL) cytotoxic effect on the cancerous cell line (MCF-7). In general, the compound showed moderate acetylcholinesterase enzyme activity (IC50: 115.63 ± 1.16 µg/mL), high butyrylcholinesterase (IC50: 3.12 ± 0.04 µg/mL), antiurease (IC50: 1.10 ± 0.06 µg/mL), and antithyrosinase (IC50: 11.52 ± 0.46 µg/mL) enzyme activities. In addition, the compound was found to be effective against Escherichia coli (ATCC 25922) bacteria studied at concentrations of 6.50 mg/mL. Moreover, the test results of the boronic ester compound used in the cream formulation demonstrated that it was microbiologically and dermatologically appropriate. Histologic analysis showed that the control group and experimental group were at similar properties without significant change. The phenyl boronic acid derivative compound synthesized from quercetin may have higher biological activity potential than quercetin. Due to the high biological activity potential of the synthesized compound, it has the potential to be used in food, feed, pharmaceutical and cosmetic industries.

In-situ Raman spectroscopic studies on electrochemical oxidation behavior of chromium in alkaline solution

The electrochemical oxidation mechanism of Cr in alkaline solution was deduced by combining electrochemistry with in-situ Raman spectroscopy. • Combined electrochemistry and in-situ Raman spectroscopy to study the electrochemical oxidation behavior of chromium in the alkaline condition. • A method for the determination of chromate by chromium electrode was presented. • The method can be applied to the determination of chromate in the electroplating solution. Chromium is a metal with high hardness, and strong oxidation resistance, doping chromium in the alloy will improve the alloy's oxidation resistance and corrosion resistance. However, the mechanisms of chromium electrodeposition, electrochemical oxidation, and corrosion are still controversial and only stay in the field of electrochemical research and lack in-situ data support. Therefore, we combine electrochemistry and in-situ Raman spectroscopy to study the electrochemical oxidation behavior of Cr in 0.5 M NaOH solution. The results show that the electrochemical oxidation behavior of Cr in the alkaline solution includes two steps. The first step is that the Cr layer loses six electrons and combines with OH − oxidized to CrO 4 2− , the second step is CrO 4 2− enriched on the Cr layer, and the Cr layer loses six electrons again oxidized to Cr 2 O 7 2− . We develop an electrochemical method for CrO 4 2− concentration detection in the chromium plating solution based on this mechanism. We obtain the linear correlation curve between CrO 4 2− concentration (0.1∼2.0 mol·L −1 ) and peak current density, which has simple, fast, and broad linear range characteristics.

RETRACTED: 4-dimethylaminopyridine: Discovery of a co-reactant system providing outstanding and reliable emission in electrochemiluminescence

• 4-DMAP, a novel co-reactant, has been explored for improving Ru(bpy)32 + ECL. • Ru(bpy)32+/4-DMAP system enhances 28 times stronger ECL emission than Ru(bpy)32+/TPrA system. • It exhibits electrochemical oxidation behaviour like TPrA. • The efficient ECL is in the pH range of an environmental and biological system or immunoassay. Ru(bpy) 3 2+ has received significantly increasing interest in clinical diagnosis and scientific research because of its high sensitivity, wide dynamic range, good stability, solubility, and ECL efficiency in aqueous solutions. As the electrochemiluminescence (ECL) results from electrochemical reactions between Ru(bpy) 3 2+ and co-reactant, extensive research has been focused on exploring novel co-reactants for the highly sensitive determination of Ru(bpy) 3 2+ . Therefore, co-reactant plays a critical role for the electrochemiluminescence (ECL) application. Herein, 4-DMAP has been explored as a potential co-reactant for enhancing Ru(bpy) 3 2+ ECL. It is much more effective than tripropylamine (TPrA) at gold and platinum electrodes, although it shows an ECL emission mechanism similar to TPrA. The presence of amine group at para position with pyridine ring in 4-DMAP structure considerably enhances ECL intensity. The ECL intensities of the Ru(bpy) 3 2+ /4-DMAP system are approximately 28 and 25 times stronger than that of the Ru(bpy) 3 2+ /TPrA system at gold and platinum electrode, respectively.

Effect of magnetic field on the behavior of Electrochemical oxidation of Aluminum in 3.5% NaCl solution

An irreversible electrochemical reaction from material interaction with the environment and causing degradation is known as corrosion. The electrolyte changes significantly affect the corrosion's reaction kinetics. Unknown factors and various notable factors influence the corrosion rate of a particular material in the environmental system. Significant interest in magnetic fields and their effects on electrochemical reactions have recently been gained. This paper studies the effect of an external magnetic field on the electrochemical oxidation of Aluminum (Al) in a 3,5% NaCl solution. The magnetic field 0; 0,8; 1,4; and 2,1 Tesla were used to expose the samples during corrosion testing. We found that the effect of a magnetic field on electrochemical oxidation shifts the oxidation potential to higher or lower than the oxidation potential without a magnetic field. Moreover, the oxidation potential's value depends on the magnetic field's intensity.

Oxidation mechanism of arsenopyrite under alkaline conditions: Experimental and theoretical analyses

In this study, arsenopyrite leaching test was conducted by sodium hydroxide solution with pH = 10, 12, and 13.5. The electrochemical oxidation behavior of arsenopyrite in sodium hydroxide solution at pH = 10, 12, and 13.5 was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. The elemental composition and chemical state of arsenopyrite after surface oxidation was investigated by X-ray photoelectron spectroscopy. The hydroxylation and electronic configuration of surface atoms of arsenopyrite were calculated by density functional theory. The concentration of Fe3+ in the solution was found to increase by one order of magnitude with increasing pH of the sodium hydroxide solution. The total As content in the solution also increases with increase in pH value as a result of sharp increase in the ratio of As(Ⅲ)/As(Ⅴ). In sodium hydroxide solution with pH = 10, the surface of arsenopyrite undergoes two oxidation stages. At pH = 12 and 13.5, the second stage (oxidation of the S-rich zone) disappears. The hydroxylation of Fe and As atoms on the arsenopyrite surface is the first step in the oxidation process. As atoms are then oxidized to As(Ⅲ) and enter the solution while Fe and S atoms form Fe(OH)3 and S-rich zone covering the arsenopyrite surface. Finally, As(Ⅲ) in the solution is oxidized to As(Ⅴ), and the S-rich zone is oxidized to SO42−. The oxidation dissolution rate of arsenopyrite increases sharply with increasing pH. The research results have important theoretical significance for the backfilling process of tailings containing arsenopyrite.

Evaluation of Antioxidants Using Electrochemical Sensors: A Bibliometric Analysis

The imbalance of oxidation and antioxidant systems in the biological system can lead to oxidative stress, which is closely related to the pathogenesis of many diseases. Substances with antioxidant capacity can effectively resist the harmful damage of oxidative stress. How to measure the antioxidant capacity of antioxidants has essential application value in medicine and food. Techniques such as DPPH radical scavenging have been developed to measure antioxidant capacity. However, these traditional analytical techniques take time and require large instruments. It is a more convenient method to evaluate the antioxidant capacity of antioxidants based on their electrochemical oxidation and reduction behaviors. This review summarizes the evaluation of antioxidants using electrochemical sensors by bibliometrics. The development of this topic was described, and the research priorities at different stages were discussed. The topic was investigated in 1999 and became popular after 2010 and has remained popular ever since. A total of 758 papers were published during this period. In the early stages, electrochemical techniques were used only as quantitative techniques and other analytical techniques. Subsequently, cyclic voltammetry was used to directly study the electrochemical behavior of different antioxidants and evaluate antioxidant capacity. With methodological innovations and assistance from materials science, advanced electrochemical sensors have been fabricated to serve this purpose. In this review, we also cluster the keywords to analyze different investigation directions under the topic. Through co-citation of papers, important papers were analyzed as were how they have influenced the topic. In addition, the author’s country distribution and category distribution were also interpreted in detail. In the end, we also proposed perspectives for the future development of this topic.

β-Cyclodextrin capped gold nanoparticles and nanodiamond assembled on a porous gold mini-chip as a disposable electrochemical sensor for bisphenol A

ABSTRACT Herein, a disposable electrochemical sensor was constructed from a gold DVD (GDVD) mini-chip modified with pores, β-cyclodextrin capped gold nanoparticles (AuNPs@β-CD), and nanodiamond (ND). For this purpose, the LSV method was employed to deposit a silver film on the surface of the mini-chip. Then, the silver was replaced with gold using galvanic replacement, after which etching of silver by nitric acid and ammonia was accomplished to obtain a porous GDVD mini-chip (PGDVD). Next, AuNPs@β-CD and thereafter, an aqueous ND dispersion were successively drop-cast on the PGDVD. Finally, the as-prepared mini-chip was exposed to air to obtain the PGDVD@AuNps@β-CD@ND mini-chip. The electrochemical oxidation behaviour of BPA showed an irreversible oxidative wave with decreased oxidation overpotential and increased current response for BPA. The calibration curve was linear over the concentration range of 5 × 10−5 M to 1 × 10−3 M of BPA. According to the 3sb/m and 10sb/m criteria, the limits of detection (LOD) and quantitation (LOQ) of the method were obtained to be 1 × 10−5 M and 5 × 10−5 M, respectively. Also, the reproducibility of the method (RSD%) was obtained to be 4%. The proposed sensor was employed for the analysis of spiked tap water and apple juice samples.

Proving the Availability of Ni–Fe Anode for Electro-Reduction of Solid V2O3 in Molten Fluoride Salts

The availability of casting Ni–Fe alloy as inert anode for direct electro-reduction of V2O3 in molten Na3AlF6-K3AlF6-AlF3 was investigated. The electrochemical oxidation behavior of anode as well as microstructural evolutions of formed oxide scale were systematically studied. The electrochemical characterization and reaction mechanism of the cathode oxide were also investigated to evaluate the influence of alloy anode on cathodic reduction process. The in situ formed three-layered oxide scale is compact and coherent, which is composed of an outermost Fe2O3 + FeAl2O4 skin layer, a Fe2O3 middle layer and a FeAl2O4 inner layer. The skin layer has a continuous, smooth structure and shows electrochemical activity. The Fe2O3 layer with a compact structure prevents inward diffusion of electrolyte and outward migration of metal cations. The innermost FeAl2O4 layer shows a loose structure and functions as a buffer layer to improve the peeling resistance of oxide scale. With the continuous extension of polarization time, the inner FeAl2O4 layer is slowly oxidized and becomes thinner, simultaneously, the dense Fe2O3 layer becomes thicker. Ultimately, metal vanadium product with fine rod-like particles can be obtained and the oxygen content in the metal vanadium is below 0.3 mass% within electrolyzing time of 2 h. The corresponding current efficiency is around 63%.

Electrochemical saturation of antimony-lead melts with oxygen: Cell design and measurement

Liquid metals have emerged as potential materials for fuel cell and battery applications due to their suitable redox potentials, fast redox kinetics, and/or active participation in electrode reactions. In this work, we study the electrochemical oxidation behavior of antimony-lead melts by the use of a robust, yttrium-stabilized zirconia based, test setup that can avoid the necessity for the use of precious metals as current collectors. Impedance spectroscopy results obtained at 700°C as a function of applied anodic polarization reveal the presence of two main contributions: an interfacial resistance, occurring at high-frequencies, related to the transference of oxygen-ions between the electrolyte and the anode melt and a low-frequency contribution, related to the diffusion of oxidized species within the bulk of the melt. These electrode mechanisms were followed as a function of the extent of melt oxidation, with suggested links made to the degree of melt segregation supported by SEM and XRD analyses.

ZIF-L Derived Bimetallic N-Doped Porous Carbon-Prussian Blue Composite as Efficient Catechol Electrochemical Sensor

The development of effective and accurate catechol (CC) electrochemical sensors is critical for environment and life health perspectives. A facile pyrolysis of 2D bimetallic (Zn/Co) zeolitic imidazolate framework (Zn/Co-ZIF-L) was employed to prepare Zn and Co nanoparticles encapsulated in N-doped porous carbon (Zn/Co@NPC). Prussian blue (PB) was synthesized in situ via the co-precipitation of ferricyanide ([Fe(CN)6]3−) and iron (II) ion originated from the reduction of Fe3+ by Zn/Co@NPC and then served as the main active substance of CC detection. The morphology and composition of the final composite Zn/Co@NPC-PB were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). The Zn/Co@NPC-PB modified glass carbon electrode (GCE) exhibits two concentration linear ranges of 4.13 μM − 1.08 mM (R2 = 0.999) and 1.08 mM−11.82 mM (R2 = 0.999) for CC electrochemical detection with a limit of detection 1.05 μM (S/N = 3). At the same time, the Zn/Co@NPC-PB/GCE shows great selectivity to electrochemical oxidation behavior of CC in presence of 20 folds dihydroxybenzene interferents such as hydroquinone and resorcinol. Furthermore, it showed a long-term stability and near 100% recovery for the detection of a real sample in Yellow River water.

Influence of Ferric Ions on the Electrochemical Dissolution Behaviors of Arsenopyrite in Sulfuric Acid of pH 1

ABSTRACT This study investigated the electrochemical oxidation behaviors of arsenopyrite in sulfuric acid (pH 1) containing various concentrations of ferric ions by cyclic voltammetry, Tafel polarization curves and electrochemical impedance spectra (EIS) measurements. Results indicated that the addition of ferric ions did not affect the electrochemical dissolution mechanism of arsenopyrite. With the increase of the ferric concentration, the corrosion potential of arsenopyrite shifted positively, and the corrosion current density increased. EIS tests showed that arsenopyrite oxidation consisted of two charge transfer processes, i.e., the release of iron and arsenic from arsenopyrite lattice and the oxidation of elemental sulfur formed on the arsenopyrite surface. The overall oxidation of arsenopyrite was controlled by the oxidation of elemental sulfur. The presence of ferric ions decreased the electron transfer resistances of both processes, contributing to the accelerated dissolution of arsenopyrite. Cyclic voltammetry and Tafel plots implied that the enhanced cathodic reaction was the dominant reason for the improved dissolution of arsenopyrite in the presence of ferric ions.

Alternating current-enhanced carbon nanotubes hollow fiber membranes for membrane fouling control in novel membrane bioreactors

A novel electro-assisted membrane bioreactor (EMBR) was built up with alternating current (AC) voltage applying on carbon nanotubes hollow fiber membranes (CNTs-HFMs) as the basic separation unit (AC-EMBR). Herein, a combination effect of electrostatic repulsion, electrochemical oxidation and translational motion behaviors was used to mitigate membrane fouling with +1.0 V for 1 min and −1.2 V for 1 min repeatedly applying on CNTs-HFMs. During the 73-day operation, the CNTs-HFMs in AC-EMBR exhibited a superior antifouling capability with a lower average fouling rate of 0.017 bar/d comparing to control groups, which were 0.021 bar/d in EMBR with CNTs-HFMs as cathode (C-EMBR), 0.025 bar/d in EMBR with CNTs-HFMs as anode (A-EMBR) and 0.029 bar/d in MBR without voltage, respectively. The AC potential led pollutants to loosely attach on membranes, which reduced irreversible fouling as well as reduced unrecoverable fouling levels. Bound extracellular polymeric substances (EPS) concentration in biomass of AC-EMBR was lower than those in the other reactors, which also contributed to suppressing membrane fouling. Meanwhile, an excellent effluent quality was obtained in AC-EMBR with COD removal rate higher than 96% and effluent NH4+-N concentration lower than 2 mg/L. Microbial community diversity has been promoted by AC electric field according to the microbial community analysis. The results of this study suggested the effectiveness of utilizing AC for membrane fouling mitigation and wastewater treatment in MBR systems.

In-Situ Electrochemical Mapping of Lithium-Sulfur Battery Interfaces Using AFM-SECM

Although lithium-sulfur (Li-S) batteries hold significant promise as the next-generation technology to replace lithium-ion batteries, their development is still hampered by several challenges such as rapid capacity fade, short cycle life, and poor coulombic efficiency(1, 2). To address these issues, extensive research efforts were devoted to finding better electrode and electrolyte materials. However, only a limited emphasis was given towards understanding the true nature of lithium polysulfides (LiPS) interactions at the electrode/electrolyte interface mainly due to the nonexistence of a comprehensive tool to grasp the working mechanism in real-time. While much of the in-situ studies envisage the nature of LiPS reactivity along with their chemical identity in different electrolytes(3-6), a detailed temporal and spatial mapping of LiPS interactions on the electrode surface is not explored much(7, 8). Herein, we introduce the atomic-force-microscopy-based scanning electrochemical microscopy (AFM−SECM) technique to study the Li−S interfacial redox reactions at nanoscale spatial resolution in real-time. In situ electrochemical mapping of the discharge end products during oxidation revealed heterogeneity in the particle’s electrochemical activity and spectroscopic evidence demonstrated the presence of Li2S and Li2S2 species. During charging, Li2S2 was found to undergo facile oxidation compared to Li2S to produce intermediate LiPS. Subsequently, the unoxidized Li2S chemically/electrochemically reacts with the intermediate LiPS. At higher oxidation potentials, the as-reacted LiPS turns into insulating products, which accumulate over cycling, resulting in the reduction of active material utilization and ultimately leading to capacity fade. The interdependence of the topography and electrochemical oxidative behavior of Li2S on the carbon surface by AFM−SECM reveals the Li2S morphology−activity relationship and provides new insights into the capacity fading mechanism in Li−S batteries.

Cations stress on low-grade nickel sulfide ore oxidation leaching

The effects of cations stress of magnesium ion and sodium ion on the low-grade nickel sulfide ore oxidative leaching in simulated sulfuric acid solutions were investigated. This study was performed in two courses, including the effect of the cations on the valuable metals leaching efficiencies of the nickel ore and its influences on the electrochemical oxidation behavior of the nickel ore. The leaching results present that parts of magnesium-containing gangues and ferrous sulfide are preferentially dissolved into lixivium, and the leaching efficiencies of Ni and Cu decreased much related to the leached concentrations of Mg2+ increased. The results of electrochemical measurements show that the oxidation leaching of the low-grade nickel sulfide ore is controlled by the intermediates oxidative diffusion. Mg2+, as well as Na+, affects the transformations of the Fe3+/Fe2+ couple and sulfur-containing species, and those cations are apt to be attracted by the anions and directionally adhere to the negative active site of the metal sulfide surface, causing an increase in the electrochemical activities, which facilitates the electron transfer between the ore and leaching mediums. By comparative study of the role of Mg2+ and Na+, it is found that Mg2+ negatively affects the oxidative diffusion of the intermediates through promoting the generation of a compact film, which lowers the metals leached efficiencies, and the unfavorable effect of Na+ tends to be the coupled effect of the leached Mg2+ and Fe3+.

Anodic Stripping Voltammetric Methods for Determination of Brexpiprazole and its Elec-Trochemical Oxidation Behavior in Pure Form and Pharmaceutical Preparations

Anodic Stripping Voltammetric Methods for Determination of Brexpiprazole and its Elec-Trochemical Oxidation Behavior in Pure Form and Pharmaceutical Preparations

Investigation of Electrochemical Oxidation Behaviors and Mechanism of Single-Crystal Silicon (100) Wafer under Potentiostatic Mode

Electrochemical oxidation (ECO) has been used widely to oxidize single crystal Si wafers. Aiming at optimizing the ECO assisted machining methods, the oxidation behaviors of single- crystal silicon (100) wafer under potentiostatic mode are experimentally investigated. It is shown that the Si wafer can be electrochemically oxidized and the oxidized film thickness reaches to 239.6 nanometers in 20 min. The hardness of the oxidized surface is reduced by more than 50 percent of the original surface. The results indicate that the oxide thickness and the hardness can be controlled by changing the voltage. Based on the experimental findings, a hypothesis on the ECO mechanism under potentiostatic mode was proposed to explain the fluctuations of current density under specific applied voltage. The occurrence of the multiple peaks in the current density curve during the oxidation process is due to the formation of discharge channels, which was initiated from the defects at the interface between the oxide bottom and the substrate. This breaks the electrical isolation and leads to the discontinuous growth of the electrochemical oxide layer. The present work contributes to the fundamental understanding of the ECO behaviors for the single-crystal Si (100) wafer under potentiostatic mode.