Solute permeation through perfluorocarboxylate membranes

The sorption and permeability of tetraalkylammonium chlorides and alkali chlorides in perfluorocarboxylate membranes were determined. The water content and density of the membranes were found to change with treatment in boiling water and with different tetraalkylammonium cations as counterions for the carboxylate fixed charge. This is attributed to a change in the structure of the membrane matrices. DSC measurements suggested the existence of three distinct phases in the membranes, i.e. a free water phase, a bound water phase, and nonfreezable water. The nonfreezable water was assumed to be in the fluorocarbon phase. The permeability sequence of the tetraalkylammonium chlorides was found to be TEACl > TMACl > TBACl. To interpret the results, a parallel permeation model was proposed.     

The effect of the concentration of TBACl on the electrodeposition of zinc from chloride and perchlorate electrolytes

The effect of the concentration (5 to 220 mg l^–1) of tetrabutylammonium chloride (TBACl) on zinc deposition overpotential and on the degree of levelling of Zn electrodeposited on a Zn RDE was studied by cyclic voltammetry, galvanostatic measurements and SEM examination. The overpotential for Zn electrodeposition initially increases with increasing TBACl concentration until reaching a limiting value, at which point the surface becomes blocked by adsorbed TBA⁺. The optimum degree of deposit levelling is obtained for intermediate TBACl concentrations, whose value depends on the concentration (1 or 2.5m) of NaCl supporting electrolyte. When NaClO₄ is substituted for NaCl in the bath, the overpotential for Zn electrodeposition markedly increases and consequently the levelling power of TBACl decreases.     

Effect of chromate ion on zinc electrowinning from acid sulphate electrolyte

The effect of chromate ion and its interaction with antimony and glue on zinc electrowinning from acid sulphate electrolyte were studied. During electrolysis at 430 A m^–2 and 45°C, the chromate ion was found to polarize the cathodic reaction resulting in a refined zinc deposit having a morphology featuring a vertical orientation of the zinc platelets. Although chromium did not codeposit, the current efficiency for zinc deposition was dramatically decreased in the presence of > 1000 mg dm^–3. This effect became more pronounced when the electrolyte also contained additives such as antimony and glue.     

Zinc deposit structures obtained from synthetic zinc chloride electrolyte

Zinc deposits electrowon from synthetic zinc chloride electrolyte were characterized by a morphology which featured clusters of large platelets with rounded edges and by a preferred crystallographic orientation, namely (0 0 2) (1 0 3) (1 0 5). These deposit characteristics persisted over a wide range of experimental conditions which included variations in the current density and changes in anode material, cell design, and the zinc and hydrochloric acid concentrations. Although the addition of HCl to the electrolyte improved the physical characteristics of the deposit, it did not alter the deposit morphology or orientation. The addition of animal glue or tetrabutylammonium chloride resulted in smooth, compact deposits having a (1 1 0) orientation at 0·24 M H⁺. Jaguar C-13 additions gave a (1 1 2) orientation, while gum arabic and tetraethylammonium chloride only affected the grain size. The various deposit morphologies and orientations obtained showed only some correspondence to changes occurring in the zinc deposition polarization voltages. The presence of metallic impurities, Cu, Co, Fe, and Sb, caused the morphology and orientation of the deposits to become more basal and the current efficiency to decrease. The presence of Cd resulted in a (1 1 2) (1 1 4) orientation and Pb gave a (1 0 1) orientation.     

The effect of cadmium on zinc deposit structures obtained from high purity industrial acid sulphate electrolyte

The effect of cadmium on cathodic zinc crystal growth was studied in high purity industrial electrolyte, with and without additives, in an attempt to establish a correlation between morphology, polarization and the extent of cadmium contamination. Cadmium additions to acid zinc sulphate electrolyte did not have a significant effect on the zinc deposit orientation but did substantially refine the deposit grain size. The refinement in deposit grain size is directly related to the level of cadmium in the zinc deposits. Cadmium, in combination with glue and optimum amounts of glue and antimony, also reduced the deposit grain size: the preferred deposit orientation remained (1 1 2) with a slight tendency to (1 0 1) at high glue concentrations. Cadmium in combination with antimony resulted in an increased depolarization of zinc deposition and a basal (0 0 2) deposit orientation. Lead additions to zinc electrolyte containing cadmium resulted in increased deposition overpotentials and intermediate to vertical deposit orientations.     

Aluminium cathode effects in zinc electrowinning from industrial acid sulphate electrolyte

The effects of aluminum cathode grain size and surface conditioning treatments on zinc electrodeposition from purified industrial acid sulphate electrolyte were investigated. The Al cathode grain size had no effect on the long-time (15–60 min) deposit characteristics although deposits obtained using large-grain Al cathodes were often easier to strip. A study of the initial zinc nucleation (5–80s) showed that fine-grain Al cathodes had more zinc nucleation sites than largegrain cathodes. The influence of cathode preconditioning and glue on the initial zinc nucleation were also determined.     

Corrosion of the zinc negative electrode of zinc–cerium hybrid redox flow batteries in methanesulfonic acid

Corrosion of zinc in aqueous methanesulfonic acid has been evaluated over a wide range of concentrations of acid (0.5–5 mol dm^?3), dissolved zinc (0.5–2 mol dm^?3), and electrolyte temperature (22–50 °C). The corrosion rate of zinc, in terms of weight loss and the volume of hydrogen evolved, varied with time and it was found to be highly dependent on the surface state and electrolyte conditions. With an initial active layer of zinc present, the corrosion rate rapidly increased following a decline when the proton concentration in the solution decreased to ca. 0.56 mol dm^?3. Organic and inorganic inhibitors were added to the electrolyte to suppress the zinc corrosion in 1 mol dm^?3 methanesulfonic acid. The strong adsorption and blocking effects of cationic organic adsorption inhibitors, such as cetyltrimethyl ammonium bromide and butyltriphenyl phosphonium chloride, led to a significant decrease in zinc corrosion over a 10 h immersion period. With the addition of indium and lead ions inhibitors, the zinc surface showed less activity. Zinc corrosion continued to a smaller extent in the presence of these metallic inhibitors during the first few hours, but the metallic layer of the inhibitors did not cover the surface completely resulting in continued hydrogen evolution and making the inhibitors less effective at longer times.     

Hydrogenation of Tasmanian alginite in the presence of tin(II) chloride and zinc chloride

A Mersey River (Tasmanian) alginite concentrate was heated (3 °C min^?1) to temperatures of 200–480 °C in a small capacity, high-pressure, single-cell differential thermal analysis, batch autoclave under nitrogen or hydrogen (initial pressure 9.8 MPa) with or without 10 wt% zinc chloride or tin(II) chloride. An organic solvent (vehicle) was not used in these experiments. Although there is an almost complete conversion of alginite to gaseous and liquid products between 425 and 450 °C, the compositions of the autoclave gas samples, the yields and compositions of the hexane-soluble material derived from the autoclave products, and the optical properties of the hexane-insoluble residues, reflect the experimental conditions, in particular the influence of the metal chlorides. Principal phases of hydrogen uptake by alginite occur at different temperatures in a hydrogen atmosphere depending on the presence and nature of the metal chloride. The autoclave gas compositions reveal a clear distinction between the uncatalysed and catalysed experiments. The hydrocarbon gas ratios permit a distinction to be made between catalytic (carbonium ion mechanism) reactions and thermal (free radical mechanism) reactions; at higher temperatures the latter are dominant, even in the catalysed experiments. The metal chlorides lower the organic sulphur and nitrogen contents of the hexane-soluble material; zinc chloride being more effective than tin(II) chloride. Incident light fluorescence microscopy suggests that zinc chloride and tin(II) chloride give rise to different hydrogenation reactions between 300 and 425 °C. Incident light fluorescence microscopy is a most useful method of studying the petrography of alginite in the hexaneinsoluble residues.     

Electrodeposition of nickel-cobalt-zinc alloys from a borate bath

The electrodeposition has been studied of nickel-cobalt-zinc alloys from a borate bath containing nickel sulphate (120–140 g dm^–3), cobalt sulphate (30–46 g dm^–3), zinc sulphate (144–168 g dm^–3), boric acid (30 g dm^–3) and ammonium chloride (2 g dm^–3). The operating conditions were: current density, 2.0–5.0 A dm^–2; temperature, 30–40°C and pH, 2.4 to 5.4. Light grey, semibright, stressed films have been obtained. However, the deposits consist partially of black powder when the concentration of the various components is increased. The brightness is found to increase with decreasing temperature and pH of the solution. The total cathode efficiency increases when the pH and temperature of the solution decrease, whereas at any particular pH and temperature it first decreases, reaches a minimum and then increases with increasing current density.     

Friedel-Crafts acylations with modified clays as catalysts

Friedel-Crafts acylations are very effectively catalyzed by clays modified through exchange of the interlamellar cations or through impregnation of metal chlorides. The acidic K10 montmorillonite exchanged with iron(III) gives outstanding results in quantitative (98–100%) acylation of anisole (15 min), mesitylene (15 min), and p-xylene (3 h) at 140–160 °C. Clays impregnated with zinc chloride, such as the K10 montmorillonite, or Japanese acidic clay show near-equivalent catalytic performance.     

Effect of sodium and potassium sulphates on zinc electrowinning

In order to evaluate the intrinsic effect of high concentrations of sodium and potassium sulphates in zinc electrowinning solutions, measurements of coulombic efficiency were carried out under mass transfer-controlled conditions in synthetic solutions of very high purity. A solution composition of 1 mol dm^–3 ZnSO₄+1.5 mol dm^–3 H₂SO₄ was employed with and without additions of 0.5 mol dm^–3 Na₂SO₄ and/or 0.25 mol dm^–3 K₂SO₄. With temperature and current density similar to plant practice (37° C, 650 A m^–2) and electrode rotation rates of 10 and 45 s^–1, the coulombic efficiency for three successive batch tests (200 mg zinc) increased by an average of 1.2% (from an average of 96.0%) for additions of 0.5 mol dm^–3 Na₂SO₄+0.25 mol dm^–3 K₂SO₄. The results were evaluated in terms of available theories, solution purity and predicted changes in solution composition (zinc and hydrogen ion activities) and physical properties following additions of Na₂SO₄/K₂SO₄. It was concluded that in the plant situation the increase in coulombic efficiency would probably be offset by an increase in cell voltage of about 2%, the net effect on power efficiency being a decrease of about 1%. The zinc deposit morphology and preferred orientation were also studied. The addition of sodium and/or potassium sulphate to the solution resulted in rougher, darker zinc deposits, a slight grain refining effect, and a change from random to predominantly basal (002), (004) crystal orientation (at 45 s^–1).     

Selective Transport of Cu(II) across a Polymer Inclusion Membrane with 1-Alkylimidazole from Nitrate Solutions

The selective transport of copper(II), zinc(II), cobalt(II), and nickel(II) ions from nitrate solutions across polymer inclusion membranes (PIMs), which consist of cellulose triacetate as polymeric support, o-nitrophenyl pentyl ether as plasticizer, and 1-alkylimidazole (alkyl from hexyl- to decyl) as ion carrier was reported. PIM was characterized by using atomic force microscopy (AFM) technique. The results show that Cu(II) can be separated very effectively from other transition metal cations as Zn(II), Co(II), and Ni(II) (at a concentration of 10^?3 mol/dm³ each). Alkyl substituents at position 1 of the imidazole ring have been found to affect the hydrophobic properties and initial flux of the transported metal ions. The efficiency of separation of metal ions by 1-alkylimidazole followed the sequence: Cu(II) > Zn(II) > Co(II) > Ni(II). The highest selectivity coefficient for Cu(II) was found with 1-hexylimidazole and its 1 mol/dm³ solution in PIM. Separation of the ions was more effective for the nitrates(V) than for chlorides.     

The effect of thiourea on zinc electrowinning from industrial acid sulphate electrolyte

The effect of thiourea, with and without glue and antimony additions, on the current efficiency (CE) and polarization behaviour of zinc deposition and on the morphology and preferred orientation of the zinc deposits electrowon (at 430 A m^–2 and 35°C) from industrial acid sulphate electrolyte (55 g l^–1 Zn and 150 g l^–1 H₂SO₄) has been determined. Increasing concentrations of thiourea in the electrolyte decreased the CE for zinc deposition; the additional presence of antimony did not significantly alter the decrease in CE but the presence of glue resulted in a further substantial decrease in CE. Thiourea changed the zinc deposit morphology and orientation, and also altered the shape of the zinc deposition cyclic voltammogram.     

The effects of saponin,antimony and glue on zinc electrowinning from Kidd Creek electrolyte

The effects of Saponin alone and in combination with antimony and glue on zinc deposition current efficiency and polarization and on the morphology and orientation of 6h and 24h zinc deposits electrowon at 500 A m^–2 and 38°C from Kidd Creek zinc electrolyte were determined. Saponin, at concentrations to 100mgl^–1, was weakly polarizing, changed the preferred deposit orientation from basal to intermediate and decreased the current efficiency. At optimum glue + antimony levels, Saponin concentrations 5mgl^–1 resulted in an increase in zinc deposition current efficiency and consistently gave either a <114><112><103><102><101> or a <101><112> preferred deposit orientation depending on the antimony + glue combination used. Tests run for 24h for selected combinations of Saponin, antimony and glue confirmed the results obtained for the 6h studies.     

The effects of As(III) and As(V) on zinc electrowinning from industrial acid sulphate electrolyte

The effects of As(III) and As(V), with and without glue and glue+antimony additions, on the current effeciency and polarization behaviour of zinc deposition and on the morphology and preferred orientation of 1-h zinc deposits electrowon from industrial acid sulphate electrolyte have been determined. As(III) had no effect on the current efficiency and did not alter significantly either the zinc deposition polarization curve or the zinc deposit morphology and orientation. Increasing concentrations of As(V) resulted in a significant decrease in the current efficiency for zinc deposition from addition-free electrolyte and from electrolytes containing added glue and glue+antimony. As(V) also changed the zinc deposit morphology and orientation, and significantly altered the shape of the zinc deposition cyclic voltammogram.     

Electrochemical Recovery of Lithium Ions in the Aqueous Phase

Abstract

The electrochemical insertion of lithium ions into a Pt/λ-MnO₂ electrode was investigated in various metal chloride solutions. The Li⁺ insertion occurred effectively in LiCl solutions with higher concentration than 10 mmol/dm³, but it could hardly occur in a 0.1 mmol/dm³ LiCl solution. Alkaline earth metal ions showed a stronger inhibition effect against the Li⁺ insertion into the Pt/λ-MnO₂ electrode than alkali metal ions. However, since only Li⁺ ions were taken up from a mixed solution of lithium and alkaline earth metal chlorides, a high selectivity of the electrode for lithium ions was shown.

It was possible to recover lithium ions from geothermal water by this electrochemical method using the Pt/λ-MnO₂ electrode; the lithium uptake was 11 mg/g-MnO₂.     

On the effects of antimony and glue on zinc electrocrystallization behaviour

An investigation has been made to determine the effects that additions of glue and antimony have on the electrowinning of zinc from acid sulphate solutions. In particular, the zinc crystal growth and cathode current efficiencies were studied in an attempt to establish a correlation between morphology and the nature of the additives. Operating conditions of 55 A ft^–2#x002A; and 35°C were used for most of the experiments with electrolyte concentrations of approximately 55 gl^–1 zinc and 150 gl^–1 H₂SO₄. Additional runs were made at 40,75 and 100 Aft^–2 at 30,40 and 50°C in order to verify certain trends. Primarily by means of scanning electron microscopy (SEM) techniques, it was possible to categorize deposit morphologies according to the type and concentration of the additives. The general effect of antimony was to refine the grain size and cause the basal plane platelets to lie parallel to the substrate. Glue also caused some refinement, but caused the platelets to become aligned perpendicular to the substrate. Level deposits were obtained in the latter case, which would effectively prevent dendritic growths. A relationship between the relative amounts of glue and antimony in solution and the current efficiency was also obtained.     

The effect of antimony,chloride ion,and glue on copper electrorefining

A study has been made to determine the effect of antimony, chloride ion, and glue on copper electrorefining. All deposits were made at a temperature of 65° C on a titanium cathode. Current densities of 398 A m^–2 and 133 A m^–2 were used. The deposits were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) to determine morphology and crystal orientation. Atomic absorption (AA) and Auger spectroscopy (AES) were used to study the chemical composition of the deposits and a simple bend test was used to determine structural integrity. It was found that when the antimony concentration in the electrolyte exceeded 300 ppm, brittle deposits were produced containing considerable amounts of antimony. Very small amounts of chloride ion (1.5 ppm or above) decreased the codeposition of antimony greatly and produced ductile deposits. However, at a chloride ion level of 15 ppm or above, the back side of the deposit had a very rough, powdery appearance. The effect of glue was to counteract this and to produce a mirror-like finish on the deposit back.     

Effects of salt on homogeneous succinoylation of lignocellulosic fibers in dimethyl sulfoxide/tetraethylammonium chloride under mild condition

Effects of salt in the homogeneous succinoylation of ball milled mulberry wood in dimethyl sulfoxide (DMSO)/tetraethylammonium chloride (TEACl) was investigated using viscometry and two‐dimensional nuclear overhauser effect NMR spectroscopy (2D NOESY). The intrinsic viscosity of mulberry wood solution strongly depends on the TEACl dosage indicating that the change in hydrodynamic size of polymers caused by the interactions between salt and polymers in solution. 2D NOESY spectra reveal that TEA⁺ cations bind to the cellobiose in DMSO by the interactions between methenyl of TEA⁺ and C(1)/C(1′) group of cellobiose and the intensities of the crosspeaks increased with an increase in TEACl dosage. Taking cellobiose as a model compound for cellulose, it can be expected that TEA⁺ cations and cellulose forms a polyelectrolyte‐like complex. The yields of homogeneous succinoylation of mulberry wood in DMSO/TEACl benefits from the interactions between TEA⁺ cations and cellulose evidenced by weight percent gain, Fourier transform infrared spectra as well as CP/MAS ¹³C‐NMR spectra. © VC 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41912.     

Effect of plating mode, thiourea and chloride on the morphology of copper deposits produced in acidic sulphate solutions

The influence of plating mode, chloride and thiourea (TU) on morphology of copper deposits has been studied. All experiments were conducted on disc electrodes rotating at 500 rpm and an average current density of 4 A dm⁻² to produce 10 μm thick deposits. In additive-free solutions, the use of pulsed current (PC) improved deposit morphology and brightness over DC plating. In the presence of thiourea (no Cl⁻), the deposits obtained by DC and PC plating were similar under most plating conditions. The presence of thiourea generally improved deposit quality over that obtained in additive-free solutions, but caused the formation of microscopic nodules and the deposits to appear slightly cloudy, resulting in lower reflectances than that of a polished uncoated copper surface. The addition of Cl⁻ to thiourea-containing solutions strongly influenced deposit morphology at both microscopic and macroscopic scales depending on chloride concentration and pulse conditions. It prevented nodule formation and created microscopically bright and reflective deposits, but caused extreme macroscopic roughness. Nevertheless, PC plating at 50 Hz in solutions containing appropriate amounts of thiourea and Cl⁻ was found to yield macroscopically and microscopically smooth deposits with reflectance similar to that of a polished uncoated copper substrate.