Destruction of cyanide in aqueous waste by electrochemical oxidation

A laboratory study was carried out by electrochemical oxidation to destroy cyanide in aqueous waste. The electrode used in this study was a triple oxide coated titanium based mesh type anode and a carbon cathode. Direct and indirect methods were both carried out at alkaline conditions and indirect oxidation method in the presence of chloride was found to be more efficient.     

CO oxidation catalyzed by silver nanoclusters: mechanism and effects of charge

The mechanism of the CO oxidation promoted by a neutral Ag(55) cluster was investigated extensively, using density functional theory calculations. The CO oxidation process catalyzed by anionic and cationic Ag(55) clusters was also studied, to clarify the effects of the charge state. The Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) mechanisms were discussed in detail. Six reaction pathways were found for the Ag(55)-mediated CO oxidation. It was found that the ER mechanism competed with the LH mechanism. The rate-limiting step of the CO oxidation was the reaction of CO with the Ag(55)O species. All of the anionic, neutral, and cationic Ag(55) clusters were able to promote CO oxidation at low temperatures. The present results enrich our understanding of the catalytic oxidation of CO by nano-sized Ag-based catalysts.     

TEMPO mediated oxidation of carbohydrates using electrochemical methods

The oxidation of some readily available carbohydrates was investigated in aqueous medium using a catalytic amount of 2,2,6,6-Tetramethyl-1-piperidinyl-oxy (TEMPO) as redox mediator. The regeneration of oxoammonium (active form) was electrochemically performed in alkaline medium at a glassy carbon anode and at controlled potential (0.5 V vs. AgCl/Ag). The primary alcohol groups of the carbohydrates without free aldehyde group, were selectively oxidized to the corresponding sodium uronate with high Faradaic yields. The presence of free aldehyde or hemiacetal groups leads to a decrease in selectivities towards uronic acids and increases the amount of by-products.     

Sodium sulfite: A promising reagent in the electrochemical oxidation of metallic silver

Among the complexing agents suitable for the electrochemical silver recovery, a promising one is sodium sulfite forming silver complexes with high stability constants: according to our data, log β₁ ∼ 5.3, log β₂ ∼ 8.2. This reagent is accessible and cheap, but nevertheless it almost never has been used for these purposes. We studied the stability of the sodium sulfite solutions in air and showed a possibility of using them for a long period. Using the methods of potentiodynamic polarization and potentiostatic electrolysis, we have studied characteristics of the process of metallic silver oxidation in the sulfite media. The anodic polarization process of the silver dissolution is shown to occur with 100% yield with respect to the consumed current. Simultaneously, on the cathode deposited up to 90% of dissolved silver.     

Enzymatic and electrochemical oxidation of uric acid: A mechanism for the peroxidase catalyzed oxidation of uric acid

The oxidation of uric acid has been studied by thin-layer spectroelectrochemistry using an optically transparent gold minigrid electrode and enzymatically using peroxidase. Under both enzymatic and electrochemical conditions a u.v.-absorbing intermediate (λ_max=302–304 nm between pH 7–9.3) is observed. This intermediate is proposed to be an imine-alcohol species formed by rapid hydration of the primary reaction product which is a diimine. Under the conditions employed in both the enzymatic electrochemical studies the imine-alcohol intermediate is hydrated in a first order reaction with an observed rate constant of 3.5×10^?3s^?1 between pH 7–9.3. This study establishes the similarity between the electrochemical and enzymatic oxidation of uric acid and indicates that electrochemical investigations of the redox behavior of purines can provide unique insights into their biological redox properties.     

Kinetics and mechanism of silver(I) catalyzed oxidation of coordinated formate by peroxydisulphate

Summary The oxidation of coordinated formate in the complexcis [Co(en)₂(NH₂R)(O₂CH)]²⁺ (R=H, Me or Et) by peroxydisulphate is catalyzed by Ag⁽¹⁾. Comparison between the rates of oxidation and of acid catalyzed equation of the formato complexes shows that the former is not substitution controlled. The observed pseudo first order rate constant was found to be first order with respect to the concentration of each of the reactantsi.e. the complex, Ag⁽¹⁾, and the oxidant. The rate and activation parameters for the oxidation process are reported. The major product of oxidation was found to be thecis(aquo)pentamine cobalt(III) [cis[Co(en)₂(NH₂R)OH₂]³⁺]; cobalt(II) was produced only <5%. The oxidation largely involves two electron transfer from the formate ligand, which is consistent with the hydride transfer mechanism.     

2,2-二羟甲基丁醛氧化液的高效液相色谱分析

2 ,2 二羟甲基丁酸是一种新型的化工中间体 ,用于水溶性聚氨酯涂料及高分子聚酯的制备。由于 2 ,2 二羟甲基丁醛和 2 ,2 二羟甲基丁酸的分子组成及其结构的相似性 ,决定了两者在相同的色谱条件下色谱性质极其接近。在高效液相色谱中属于难分离物质对。在HRC CN柱上 ,以二次蒸馏水为流动相 ,加入 0 .5 %磷酸调节pH ,改善了色谱峰的峰形 ,使二者的分离度达到理想效果。1　实验部分1 .1　仪器和试剂高效液相色谱仪LC 1 0AT ,紫外检测器SPD 1 0AVP ,VP ODS柱 3.5 μm ( 1 5 0× 4.6mmI.D) ,HRC CN氰基柱 3.5 μm( 1 5 0× 4.6mmI…     

Allele-specific genotyping by using guanine and gold electrochemical oxidation signals

Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-specific genotyping is also one of the important research areas, where electrochemical approaches provide promising advances. Recently reported two methods based on electrochemical guanine and colloidal gold (Au) nanoparticle oxidation signals are reviewed and compared with the existing genotyping methods in this report.     

Ethylene oxidation over silver

Ethylene oxidation on silver has been studied at 448 K and oxygen and ethylene ( ) partial pressures of 0.08 and 2×10^–5–0.02 atm, respectively. The initial reaction orders with respect to ethylene in the selective and complete oxidation on silver surface purified by oxygen and hydrogen for =0.001–0.02 atm are close to 0.30–0.35 but upon decreasing to 2×10^–5 atm, they diverge and become equal to 1.7 and 1, respectively.

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448 , 0.08 ( ) 2×10^–5–0.02 . , 0.0001–0.02 0.30–0.35, 2×10^–5 1.7 1, .

     

Review on the electrochemical oxidation of endocrine-disrupting chemicals using BDD anodes

The application of synthetic diamond-based electrodes in water treatment has been shown to be promising, especially for boron-doped diamond (BDD). With a wide potential window and high overpotential for oxygen evolution among many more excellent qualities, BDD anodes surpass the capabilities of conventional electrodes. Currently, the synthesis and fabrication of low-cost BDD anodes are still in the primary stages of development. Electrochemical oxidation of EDCs on BDD anodes in water samples have been shown to be effective with very high removal efficiencies. The presence of this group of pollutants in wastewater effluents and various water matrices causes environmental concerns and requires an immediate solution due to their persistence and threat for both humas and wildlife. Extensive research on BDD continues to be carried out with various EDCs, such as parabens and pesticides, to determine the most suitable parameters, possible mechanisms of the degradation process, and its viability in large-scale applications. These efforts remain imperative as the presence of EDCs could severely affect human health and the surrounding environment. Although significant progress has been achieved, the advanced technology is unable to achieve feasible application in a large scale due to major hindrances. In this mini review, the focus was on the recent applications of electrochemical oxidation using BDD thin-film anodes (2019 to present) for the removal of a range of EDCs. The main factors that affect the performance of BDD anodes in the electrochemical oxidation of EDCs were discussed and evaluated, highlighting some ways to overcome the issues that prevent the technology from moving onto the next stage of development.     

Controlled electrochemical growth of silver microwires

The cathodic deposition of silver whiskers as microwires in the electrochemical cell Ag/AgBr/Ag has been investigated. From growth experiments observed with an optical microscope, we conclude that the growth process occurs exclusively at the interface of the silver wires with the solid electrolyte. The basal contacts of the microwires show different morphologies without clear correlation to the substrate. The silver crystals often show a hexagonal morphology, but XRD gives no definite information on the structure of the wires. The measured exchange current density is in the order of 100 mA/cm². The growth rate and the diameter of the microwires can be controlled by variation of the current.     

A biomimetic electrochemical system for the oxidation of hydrocarbons by dioxygen catalyzed by manganese-porphyrins and imidazole.

A biomimetic electrochemical system using manganese tetraphenylporphyrin chloride and imidazole as catalysts and acetic acid as a proton donor, activates dioxygen and epoxidizes various alkenes with good yields based on consumed pairs of electrons (around 50%) and rates (around 1 turnover per min), and oxidizes alkanes into alcohols and ketones.     

Chemiluminescence of luminol catalyzed by silver nanoparticles

Silver nanoparticles (AgNPs) are synthesized by chemical reduction method and characterized by UV-vis spectra, transmission electron microscopy, and high performance particle sizer. We have found that AgNPs could enhance the chemiluminescence (CL) intensity of luminol-H(2)O(2) system. In this reaction, luminol intermediate is generated under alkaline condition on the surface of AgNPs in luminol-H(2)O(2) system and enhances CL intensity. To validate the reaction mechanism, AgNPs are bound with thioglycolic acid (Ag-HSCH(2)COOH) and then joined to BSA protein (Ag-BSA). We investigate the CL intensity in the presence of Ag-HSCH(2)COOH or Ag-BSA comparing with that in the presence of AgNPs and conclude the catalytic reaction take place on the surface of AgNPs.     

Separation of glyceride positional isomers by silver ion chromatography

Separation of triglyceride and diglyceride positional isomers by silver ion high-performance liquid chromatography coupled with an evaporative light-scattering detector is described. The triglyceride isomers had a fatty acid composition of CLC and CCL, where C and L were caprylic acid and linoleic acid, respectively. Diglyceride isomers, 1,2(2,3)-diglyceride and 1,3-diglyceride, which contained caprylic acid were separated too. A solvent system based on n-hexane, 2-propanol, ethyl acetate, and acetonitrile with a flow-rate of 0.8 ml/min was developed. Calibration curves of CLC and CCL were achieved with triolein as internal standard. Using this method, the incorporation of linoleic acid onto specific a position of glycerol backbone can be monitored.     

Direct electrochemical oxidation of polyacrylates

A promising elimination treatment of non-biodegradable organic pollutants is the direct electro-oxidation. In this work has been proposed the electrochemical elimination of polyacrylates by using boron-doped diamond (BDD) as anodic material. The complete elimination of organic contaminants has been obtained and this is the first case of successful electrochemical treatment of polymeric and bio-refractory species. The tests of the electrochemical oxidation have been conducted at constant current conditions and a complete elimination of organic species has been reached. The decrease of the COD value with time follows the behaviour of an ideal anode as in the case of low molecular organic compounds.     

Copper catalyzed oxidation of organozinc halides

A wide range of organozinc substrates may be oxidized in the presence of catalytic copper to give carbon-carbon bonds in high yield.     

Separation of positional isomers of oxidation catalyst precursors

A series of polypyridyl ruthenium complexes of the general formula [Ru(tpy)(bpy')Cl]+ where tpy is 2,2':6',2"-terpyridine and bpy' is 4-carboxy-4'-methyl-2,2'-bipyridine (4-CO2H-4'-Mebpy), a proline derviative (4-CO-Pra-(Boc)(OMe)-4'-Mebpy), or 4-((diethoxyphosphinyl)methyl)-4'-methyl-2,2'-bipyridine (4-CH2PO3Et2-4'-Mebpy) are prepared. For each complex, two isomers exist, and these are separated chromatographically. The structure of the hexafluorophosphate salt of cis-[Ru(tpy)(4-CO2H-4'-Mebpy)Cl]+, cis-1, is determined by X-ray crystallography. The salt crystallizes in the monoclinic space group Cc with a = 12.4778(6) A, b = 12.6086(6) A, c = 20.1215(9) A, beta = 107.08200(1) degrees, Z = 4, R = 0.058, and Rw = 0.072. The structures of the remaining complexes are assigned by 1H NMR comparisons with cis-1. The complexes are potentially important precursors for the incorporation of RuIV=O2+ oxidants into polymers or peptides or for their adsorption onto oxide surfaces. Preliminary electrochemical results for the isomers of [Ru(tpy)(4-CH2PO3H2-4'-Mebpy)(H2O)]2+, 4, adsorbed on ITO (In2O3:Sn) surfaces add support to a recently proposed electron-transfer mechanism involving cross-surface proton-coupled electron transfer.     

Determination of dopamine-O-sulfate and norepinephrine-O-sulfate isomers and serotonin-O-sulfate by high-performance liquid chromatography using dual-electrode electrochemical detection

This report describes the use of high-performance liquid chromatography with dual series electrode electrochemical detection to quantitate dopamine (DA)-3-O-sulfate and DA-4-O-sulfate, as well as norepinephrine (NE)-O-sulfate isomers and serotonin (5-HT)-O-sulfate. An oxidation potential was maintained at the upstream (W1) electrode, and a reduction potential at the downstream (W2) electrode. For DA-and NE-sulfates, the sulfate moiety, hydrogen and electrons are most likely removed at W1 and the corresponding quinones formed. At W2, the electrons are recaptured, creating a reductive current (peak). Results indicate that this is a sensitive procedure for the determination of DA- and NE-sulfate isomers. It is less complex than a recently developed post-column hydrolysis procedure, and is at least equivalent to that procedure in terms of specificity and lower limits of detection (less than 1 picomole) for the DA- and NE-sulfate isomers. The procedure is relatively insensitive for 5-HT-O-sulfate, as well as for tyramine-O-sulfate, homovanillic acid-sulfate and 3-methoxy-4-hydroxyphenyl glycol sulfate. It should prove useful for investigations concerning the specific conjugates of DA or NE in body tissues and fluids.