Electrochemical synthesis of thiocarbamates

The possibility of indirect and direct electrosyntheses of thiocarbamates is studied. The indirect synthesis is based on producing monochloramines by the chlorination of an aqueous solution containing an amine and sodium chloride on a dimensionally stable anode (DSA) in diaphragm electrolysis and a subsequent interaction of monochloramines with potassium xanthate. Optimum synthesis conditions are found ensuring a current efficiency for thiocarbamates of 43-60%. These are:c _amine = 0.17-2 M, c_NaC1 = 4 M,j_a = 20-30 A dm^-2, electrolysis temperature 10‡C, the chloramine : potassium xanthate : amine molar ratio of 1 : 1.1 : 2, and the temperature of the reaction between chloramine and potassium xanthate of 8‡C. The direct synthesis of thiocarbamates is realized in diaphragm electrolysis when oxidizing an aqueous solution containing an amine, potassium xanthate, and sodium chloride on DSA. With the electrosynthesis of ethyl ester of methylthiocarbamic acid as an example, conditions are found that allow one to obtain a target product with a current efficiency of about 44%. However, the direct synthesis is accompanied by the destruction of the anode material.     

Magnetic separation of heavy metal ions and evaluation based on surface‐enhanced Raman spectroscopy: Copper(II) ions as a case study

A new approach was developed for the magnetic separation of copper(II) ions with easy operation and high efficiency. p‐Mercaptobenzoic acid served as the modified tag of Fe₂O₃@Au nanoparticles both for the chelation ligand and Raman reporter. Through the chelation between the copper(II) ions and carboxyl groups on the gold shell, the Fe₂O₃@Au nanoparticles aggregated to form networks that were enriched and separated from the solution by a magnet. A significant decrease in the concentration of copper(II) ions in the supernatant solution was observed. An extremely sensitive method based on surface‐enhanced Raman spectroscopy was employed to detect free copper(II) ions that remained after the magnetic separation, and thus to evaluate the separation efficiency. The results indicated the intensities of the surface‐enhanced Raman spectroscopy bands from p‐mercaptobenzoic acid were dependent on the concentration of copper(II) ions, and the concentration was decreased by several orders of magnitude after the magnetic separation. The present protocol effectively decreased the total amount of heavy metal ions in the solution. This approach opens a potential application in the magnetic separation and highly sensitive detection of heavy metal ions.     

Numerical Study of a Free-Burning Argon Arc with Copper Contamination from the Anode

The present modeling of a free-burning argon arc accounts for copper vapor contamination from the anode. Simulations are made for an atmospheric arc that has a length of 10 mm and an electric current of 200 amps. Predicted results for two different anode evaporation rates are compared to those from a pure argon arc with no copper vapor contamination. Copper vapor concentration, temperature, electric potential, and current density profiles are presented. Included in this analysis are radiation losses from both the argon and copper by using recently calculated net emission coefficients. It was found that evaporation of copper from the anode results in a cooling of the arc in a region close to the anode, but has an insignificant influence on the arc close to the cathode. Due to the arc flow characteristics most of the copper vapor tends to be confined to the anode region.     

Electrochemical dissolution of chalcopyrite studied by voltammetry of immobilized microparticles

The characteristics of anodic electrochemical dissolution of chalcopyrite (CuFeS₂) powder in hydrochloric acid medium with sodium chloride have been studied. Cyclic voltammetry and chronopotentiometry of immobilized microparticles using paraffin-impregnated graphite electrode was employed. Present work is focused on electrochemical identification of chalcopyrite cathodic and anodic reaction products within the potential range of −0.7 to +0.8 V (vs. SCE) in hydrochloric acid solution containing sodium chloride and/or copper(II) chloride.     

Coulometric titration of copper(II) with electro-generated chromium(II)

The current efficiency for the electrogeneration of chromium(II) for use as a coulometric titrant was studied for several supporting electrolytes. With a mercury cathode and a 0.1 M chromic sulfate-0.1 M potassium chloride medium, 0.8 to 2.8 mg of copper (II) in 110 ml of solution can be titrated using potentiometric end-point detection.     

Über Kupfer(I)-carboxylate und Chlorocuprate(I)

In mixtures of 7 vol. acetonitrile and 3 vol. acetic acid, solutions or suspensions of copper(II) acetate can be reduced with hydrazine hydrate to solutions of copper(I) acetate. In this way, purely white copper(I) acetate can be isolated. Other copper(I) carboxylates can be prepared by reduction of copper(II) carboxylates or by reaction of solid carboxylic acids with copper(I) acetate. By adding acetyl chloride to solutions of copper(I) acetate in acetonitrile/acetic acid mixtures, solutions of chlorocuprates(I) are formed. From these, highly pure copper(I) chloride can be obtained. By adding alkali acetate or tetramethyl ammonium chloride to solutions of chlorocuprates(I), the pure compounds Cs₃[Cu₂Cl₅], Rb₂[CuCl₃] and NMe₄[Cu₂Cl₃] were obtained.     

苯酚在热氧化法制备的SnO2/Ti 电极上的电氧化研究

A SnO₂/Ti electrode prepared by thermal oxidation was used as the anode for galvanostatic electrolysis in acidic solution containing phenol, the time-dependances of phenol concentration,chemical oxygen demand in solution(COD)and instantaneous current efficiency were determined during electrolysis.The results show that with the SnO₂/Ti anode instead of Pt,the COD significantly decreases at the same charge passage, and average current efficiency of oxidation increases by three times The mechanism for phenol oxidation at two electrodes was discussed.     

Electrocatalysis of copper deposition from acid sulphate solutions by sulphite and selenite ions

The effects of traces of chloride, sulphur, selenium and tellurium dioxide and the selenate and tellurate ions on the electrodeposition of copper from acid copper sulphate have been studied. Low concentrations of chloride have little effect on deposition kinetics but concentrations up to 20 ppm significantly affect nodule formation. Sulphur dioxide and selenium dioxide are true electrocatalysts for deposition, with SeO₂ the more effective. Molecules in solution immediately adjacent to the electrode appear to be the active catalyst. The catalytic mechanism may be a reduction oxidation cycle involving the elements in unstable forms. The chloride ion is adsorbed according to a Langmuir type isotherm. Adsorbed chloride inhibits catalysis by SO₂ and SeO₂. The electrocatalysts have been used to demonstrate the effect of overpotential on the structure of copper deposited at constant current density.     

A solvent extraction study of molybdenum chloride and molybdenum thiocyanate complexes

The effect of reducing agents on molybdenum(VI) solutions in hydrochloric acid was studied by a solvent extraction technique to elucidate the composition of the colored molybdenum thiocyanate complex. Neither copper(I) chloride nor ascorbic acid have any effect on the extraction of MoO₂Cl₂; it is inferred that tin(II) chloride reduces Mo(VI) stepwise to a polynuclear Mo(V)·Mo(VI) complex and then to Mo(V). The colored thiocyanate complex produced by copper(I) and by ascorbic acid differs only slightly in extraction characteristics from the uncolored Mo(VI) complex. It is suggested that the color may be produced by an isomerization reaction of MoO₂(SCN)₂, and thus that the colored species may be a hexavalent rather than pentavalent molybdenum complex.     

Zeolite ZSM-5 containing copper ions: The effect of the copper salt anion and NH<Subscript>4</Subscript>OH/Cu<Superscript>2+</Superscript> ratio on the state of the copper ions and on the reactivity of the zeolite in DeNO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Isotherms of copper cation sorption by H-ZSM-5 zeolite from aqueous and aqueous ammonia solutions of copper acetate, chloride, nitrate, and sulfate are considered in terms of Langmuir’s monomolecular adsorption model. Using UV-Vis diffuse reflectance spectroscopy, IR spectroscopy, and temperatureprogrammed reduction with hydrogen and carbon monoxide, it has been demonstrated that the electronic state of the copper ions is determined by the ion exchange and heat treatment conditions. The state of the copper ions has an effect on the redox properties and reactivity of the Cu-ZSM-5 catalysts in the selective catalytic reduction (SCR) of NO with propane and in N₂O decomposition. The amount of Cu²⁺ that is sorbed by zeolite H-ZSM-5 from aqueous solution and is stabilized as isolated Cu²⁺ cations in cationexchange sites of the zeolite depends largely on the copper salt anion. The quantity of Cu(II) cations sorbed from aqueous solutions of copper salts of strong acids is smaller than the quantity of the same cations sorbed from the copper acetate solution. When copper chloride or sulfate is used, the zeolite is modified by the chloride or sulfate anion. Because of the presence of these anions, the redox properties and nitrogen oxides removal (DeNO _x ) efficiency of the Cu-ZSM-5 catalysts prepared using the copper salts of strong acids are worse than the same characteristics of the sample prepared using the copper acetate solution. The addition of ammonia to the aqueous solutions of copper salts diminishes the copper salt anion effect on the amount of Cu(II) sorbed from these solutions and hampers the nonspecific sorption of anions on the zeolite surface. As a consequence, the redox and DeNO _x properties of Cu-ZSM-5 depend considerably on the NH₄OH/Cu²⁺ ratio in the solution used in ion exchange. The aqueous ammonia solutions of the copper salts with NH₄OH/Cu²⁺ = 6–10 stabilize, in the Cu-ZSM-5 structure, Cu²⁺ ions bonded with extraframework oxygen, which are more active in DeNO _x than isolated Cu²⁺ ions (which form at NH4OH/Cu2+ = 30) or nanosized CuO particles (which form at NH₄OH/Cu²⁺ = 3).     

Electrochemical Behavior of Copper in a Water-Ethanolamine Medium

Dependences of the copper etching rate in a water-monoethanolamine medium on the solution pH and concentration of Cu(II) in the presence and absence of chloride ions are determined. An increase in the stability of univalent species and in the diffusion coefficient of Cu(I) at pH 10.30 is attributed to chelation. The mechanism of copper etching in the medium is proposed. The copper etching deceleration at pH > 10.30 is attributed to the metal blockage by surface compounds.     

Electric Field-Assisted Solid Phase Extraction: Devices, Development and Application with a Cationic Model Compound

This work describes novel devices for electric field-assisted solid phase extraction (E-SPE) and an application was carried out on the antimicrobial marbofloxacin (MAR). Conventional syringe-type SPE cartridges were easily adapted to receive two electrodes that were inserted and positioned below and above the sorbent. The adapted cartridges were coupled to a flow extraction system, which consisted of an electrophoresis power supply, a peristaltic pump and a homemade SPE manifold. These devices were used to apply electric fields during the extraction of MAR from fortified buffer and milk samples. The recovery of MAR was improved (2.3 times) or reduced (4.2 times) in comparison to conventional SPE when the top electrode was used as cathode (E-SPE_(?/+)) or anode (E-SPE_(+/?)), respectively. The results demonstrated that usual SPE cartridges can be easily and inexpensively adapted for applying an electric field in SPE. It was also concluded that the electric field applied in a usual SPE cartridge can be employed as a new suitable approach to enhance the extraction efficiency of ionic compounds in a complex sample matrix.     

TiO2纳米管阵列光电催化氧化处理氨氮废水

用电化学阳极氧化法制备了高度有序的钛基二氧化钛纳米管阵列薄膜。用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)表征样品的形貌与晶型特征。以二氧化钛纳米管阵列为光阳极,石墨为对电极,测试了不同pH值和外加偏压条件下的光电流响应和光电催化氧化降解NH4Cl水溶液(以N计,100 mg·L-1)的效率。结果表明:所制备的TiO2纳米管阵列具有锐钛矿和金红石的混晶结构,且主要晶型为锐钛矿。光电流响应的强弱与光电催化氧化效率的高低相对应,降解氨氮废水的最佳条件为pH=11,偏压为1.0 V。     

Properties of gold electrode modified with dimercaptosuccinic acid and electrochemical behavior of copper histidine complex

A self-assembled monolayer of meso-2,3-dimercaptosuccinic acid was prepared on the surface of gold disc electrode. The modified electrode was characterized using cyclic voltammetry in copper(II) solution and cyclic voltammetry and electrochemical impedance spectroscopy in the presence of potassium hexacyanoferrate( II)/(III) and hexaammineruthenium (II)/(III) chloride. Binding of copper(II) histidine complex (Cu–His) onto the electrode was successfully achieved for a wide range of tested concentrations, as shown with adsorption transfer stripping voltammetry. Electrode response (logΔI_p) was linearly proportional to logc(Cu–His) with correlation coefficient R³² = 0.9839.     

Effect of process parameters on the concentration,current efficiency and energy consumption of electro-generated silver(II)

Electro-membrane generation of Ag(II) in nitric acid was experimentally explored in a three-electrode laboratory cell with respect to various operating parameters. DSA-O₂, titanium plate and saturated Ag/AgCl were employed as the anode, cathode and reference electrode, respectively. The considered process parameters included anolyte temperature and Ag(I) initial concentration, electrolysis time, current density and supporting electrolyte concentration. Parameter effect on the Ag(II) concentration, current density and energy consumption were determined by the Taguchi and ANOVA methods for test design and data analysis, respectively. The results revealed that current density, AgNO₃ concentration and temperature had noticeable effect on the generation of Ag(II). On the other hand, AgNO₃ concentration and current density showed the most dominant effect on the Ag(II) current efficiency: 48.5% and 30.3%, respectively. AgNO₃ concentration and current density were also found to have the highest effect on the energy consumption: 72.4% and 15.9%, respectively. Validity of the Taguchi method was also assessed by collecting the actual data.     

The effects of ultrasound on the direct electrosynthesis of solid K<Subscript>2</Subscript>FeO<Subscript>4</Subscript> and the anodic behaviors of Fe in 14 M KOH solution

The effects of ultrasound on the direct electrosynthesis of solid K₂FeO₄ and the anodic behaviors of pure iron were investigated, and the physical properties of samples were characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The experimental results showed that the existence of ultrasound can decrease the formation potential of ferrate(VI) and the passivation extent of iron anode, and this leads to higher current efficiency for the direct electrosynthesis of solid ferrate(VI) at 65 °C in 14 M KOH solution. It was also found that, in the experimental scope suitable ultrasonic power (14.6 W), shorter electrolysis duration and smaller electrolysis current can improve the apparent current efficiency of the electrosynthesis, and the largest current efficiency under suitable experimental conditions reached 77.2%.     

Synthesis, spectroscopic and thermal studies of the copper(II) aspartame chloride complex

Aspartame adduct of copper(II) chloride Cu(Asp)₂Cl₂·2H₂O (Asp=aspartame) is synthesized and characterized by elemental analysis, FT IR, UV/vis, ESR spectroscopies, TG, DTG, DTA measurements and molecular mechanics calculations. Aqueous solution of the green solid absorbs strongly at 774 and 367 nm. According to the FT IR spectra, the aspartame moiety coordinates to the copper(II) ion via its carboxylate ends, whereas the ammonium terminal groups give rise to hydrogen bonding network with the water, the chloride ions or neighboring carboxylate groups. The results suggest tetragonally distorted octahedral environment of the copper ions.     

Preparing graphene oxide–copper composite material from spent lithium ion batteries and catalytic performance analysis

The wide use of lithium ion batteries (LIBs) has created much waste, which has become a global issue. It is vital to recycle waste LIBs considering their environmental risks and resource characteristics. Anode graphite from spent LIBs still possess a complete layer structure and contain some oxygen-containing groups between layers, which can be reused to prepare high value-added products. Given the intrinsic defect structure of anode graphite, copper foils in LIB anode electrodes, and excellent properties of graphene, graphene oxide–copper composite material was prepared in this work. Anode graphite was firstly purified to remove organic impurities by calcination and remove lithium. Purified graphite was used to prepare graphene oxide–copper composite material after oxidation to graphite oxide, ultrasonic exfoliation to graphene oxide (GO), and Cu²⁺ adsorption. Compared with natural graphite, preparing graphite oxide using anode graphite consumed 40% less concentrated H₂SO₄ and 28.6% less KMnO₄. Cu²⁺ was well adsorbed by 1.0 mg L^?1 stable GO suspension at pH 5.3 for 120 min. Graphene oxide–copper composite material could be successfully obtained after 6 h absorption, 3 h bonding between GO and Cu²⁺ with 3/100 of GO/CuSO₄ mass ratio. Compared to CuO, graphene oxide–copper composite material had better catalytic photodegradation performance on methylene blue, and the electric field further improved the photodegradation efficiency of the composite material.     

Electrodialytic separation of cobalt(II) and nickel(II) using liquid membranes based on tri-n-octylamine and trialkylbenzylammonium chloride

Electrodialytic separation of Co(II) and Ni(II) in the course of their transfer from 3–4 M HCl solutions into dilute solutions of various acids using liquid membranes that contain anion-exchange carriers was studied. The influence exerted on the metal transport rate and separation efficiency by the compositions of the feed and receiving aqueous solutions and of liquid membranes and by the electrodialysis current density was examined. Under optimal conditions, in metal recovery from a solution containing an equimolar mixture of 0.01 M CoCl₂ and NiCl₂, the separation factor β_Co/Ni is 147; when nickel in the feed solution is in excess, it reaches 330, and when cobalt(II) is in excess, it exceeds 400.     

Preparation of hydrophobic tannins‐inspired polymer materials via low‐ppm ATRP methods

The novel hydrophobic coating material was received for the first time by a two‐step synthetic route. Firstly, the 15‐functional brominated macroinitiator was prepared by the esterification methodology. Next step covers synthesis of star‐like polymers by poly(n‐butyl acrylate) (PBA) arms polymerization via three low‐ppm atom transfer radical polymerization (ATRP) approaches including application of copper and silver wire in SARA and ARGET ATRP, respectively, as driving forces in redox cycle of catalyst, and an external stimulus in the form of electric current (seATRP) as the third approach in copper(II) regeneration system. As expected, the electrochemically mediated technique allows synthesis of tannic acid‐inspired coating polymers in precisely controlled manner during the entire polymerization process, proved by linear first‐order kinetics plot in contrast to above‐mentioned methods, low dispersity (Ð = 1.18) of star‐shaped polymers, and high efficiency of initiation (? _i = 81%) determined after detaching of polymers side arms. Macromolecules received by all low‐ppm ATRP solutions were characterized by preserved chain‐end functionality (theoretical dead chain fraction; DCF_theo <1%). Adhesive and hydrophobic properties of received polymer materials were investigated by contact angles (θ) and free surface energy (FSE) calculations. Prepared polymer films besides excellent hydrophobic properties have great potential as a self‐healing solution.