Desorption of isoamylene from loaded acid liquors

The desorption of 2-methyl-2-butene (isoamylene) from loaded sulphuric acid solutions, having an acid strength of about 60 per cent (w/w) and loading upto 0·45 g mole of isoamylene per g mole of H₂SO₄, was found to be preceded by a fast reaction, which occurred in the film adjacent to the interface. The specific rates of desorption of isoamylene into inert hydrocarbons—n-heptane and toluene and an inert gas—nitrogen, were found to be proportional to the isoamylene concentration j, expressed as g mole of isoamylene per g mole of H₂SO₄, and agreed among themselves at the same value of j.The technique of desorption preceded by a fast reaction was employed for the measurement of effective interfacial area in liquid—liquid and gas—liquid agitated contactors. The absorption of isobutylene into fresh and loaded solutions of sulphuric acid was also used for the measurement of effective interfacial area in gas—liquid agitated contactors for comparative purposes. The values of effective interfacial area for the gas—liquid system obtained by the desorption technique were found to be comparable with those obtained from the absorption of isobutylene in fresh and loaded solutions of sulphuric acid, under otherwise comparable conditions.     

The electrodeposition of metals from their trifluoroacetate-amide baths

This paper will deal with the electrodeposition of copper and nickel from the Cu(CF₃COO)₂-HCONH₂ bath, Ni(CF₃COO)₂-HCONH₂ bath, Cu(CF₃COO)₂-HCON(CH₃)₂ bath and Ni(CF₃COO)₂-HCON(CH₃)₂ bath. The properties of these baths and the mechanism of the electrodeposition of copper and nickel from these baths were studied. While solvolysis occurs in the HCONH₂ bath, it does not occur in the HCON(CH₃)₂ bath. A complex is formed in each bath. Since the bond between the metallic ion and the solvent in the HCON(CH₃)₂ bath is stronger than that in the HCONH₂ bath, and since the dielectric constant of the solvent in the former is also lower than in the latter, is difficult to electrodeposit metal and Cu₂O is formed at cathode in the Cu(CF₃COO)₂-HCON(CH₃)₂ bath. The specific conductance in the HCON(CH₃)₂ bath is lower than that in the HCONH₂ bath. It is possible to obtain a better copper electrodeposit over a wider range of current density in the Cu(CF₃COO)₂- HCON(CH₃)₂ bath containing citric acid than in the same bath containing no citric acid. This range almost coincides with that in the Cu(CF₃COO)₂-HCONH₂ bath. While it is possible to obtain better nickel electrodeposit in Ni(CF₃COO)₂-HCONH₂ and Ni(CF₃COO)₂-HCON(CH₃)₂ baths containing appropriate additives, the range of current density which permits one to obtain a superior electrodeposit in the latter bath is narrow. The electrodeposit of nickel or copper obtained from the HCONH₂ and HCON(CH₃)₂ baths has a granular structure. The values of η_cE_c, and b_c in the copper electrodeposition reaction from the Cu(CF₃COO)₂-HCON(CH₃)₂-200 g/l citric acid bath are higher than those in the same reaction from the Cu(CF₃COO)₂-HCONH₂ bath, while the values of i_oc and α_c are lower, so the electrodeposition of copper from the former can be said to be more difficult. On the other hand, the value of n is always about 1 for both the baths. It may be concluded in view of this fact that the deposition of copper from HCONH₂ and HCON(CH₃)₂ baths takes place through Cu⁺ and that the deposition of nickel from HCONH₂ bath takes place through Ni⁺.     

The electrodeposition of zinc from acidified zinc sulphate solution

In the electrodeposition of zinc from acidified zinc sulphate solutions the loss in current efficiency (CE) due to evolution of hydrogen at the cathode has often been attributed to the presence of metal impurities, and it has been thought that in a pure solution the CE would be 100%. In this paper it is argued that, whatever the degree of purity achieved, hydrogen must always be produced simultaneously with zinc. At the start of electrolysis the CE is determined solely by the zinc/acid ratio, but when impurities are present the CE falls progressively as electrodeposition proceeds. Further, colloid silica which is always present in plant solutions is not responsible for the CE falling below 100%, nor are the lead anodes that are used in practice. Some effects of manganese, both at the anode and the cathode, are reported. The deleterious influences of cobalt and manganese together are also discussed.     

The electrodeposition of aluminium from xylene and ether-hydride electrolytes

A comparative study of aluminium electrodeposition from xylene and ether electrolytes is presented. The kinetic parameters of aluminium deposition from the tetrahydrofuran (THF) and xylene electrolytes are presented. In the case of the THF and diethylether solutions investigations of aluminium nucleation were also made. It was found that the rate of aluminium deposition was highest in the THF electrolyte composed of AlCl₃ and LiAlH₄ in a ratio 1:1. This electrolyte is recommended for deposition of aluminium protective coatings of thickness over 20 µm     

The electrodeposition of arsenic from aqueous and non-aqueous solutions

Preliminary studies of the electrodeposition of arsenic from aqueous solutions indicated that solutions of As₂O₃ in hydrochloric acid were more promising than caustic cyanide solutions. Bright, coherent coatings of arsenic of thickness not greater than 0·0005 in. were obtained from acid baths at laboratory temperature over a wide range of current densities, and As₂O₃ and HCl concentrations. The chief factor responsible for the limitation of the thickness of the applied coatings is the rapid decrease in the cathode current efficiency with time of electrolysis.The electrodeposition of arsenic from non-aqueous electrolytes has also been studied. The conductivities of arsenic-trichloride—acetone solutions have been measured at 25°C. Arsenic coatings of good quality and of thickness 10–15 × 10⁻³ in. were obtained, at high cathode current efficiencies, over a fairly wide range of operating conditions. Thick coatings of arsenic of good quality were also obtained from an arsenic-trichloride—methyl-ethyl-ketone bath operating at 20° and 80°C. Excellent coatings were obtained from an arsenic trichloride—diethyl-ketone bath operated at 100°C, but at thicknesses greater than 5 × 10⁻³ in the coatings tended to blister.The stability of arsenic and the uses of the element and its compounds in the field of corrosion protection are briefly summarized.     

The electrodeposition of metals onto polypyrrole films from aqueous solution

It is demonstrated that several metals may be electrochemically deposited onto polypyrrole films from aqueous solutions. Palladium, platinum and lead may be deposited even on thick films of the polymer (c. 0.5–2.0 m) but ruthenium only deposits on much thinner films. The effect of the polypyrrole film on the kinetics of nucleation and growth is described and the influences of the deposition potential and the thickness of the polypyrrole layer on the characteristics of the deposition reactions are discussed.     

ZnTe electrodeposition from organic solvents

The electrodeposition of zinc telluride was investigated from various organic solvent baths such as methanol, acetonitrile, propylene carbonate. The potential window increases with increasing boiling point of the solvents. In particular, ZnTe with high crystallinity could be obtained in propylene carbonate by the under-potential deposition (UPD) of Zn. The current efficiency for ZnTe deposition in propylene carbonate was enhanced considerably compared to that in acidic aqueous solutions. A single-phase ZnTe film close to the ideal stoichiometric composition of ZnTe could be obtained at 423 K and −0.8 V versus Ag/AgCl in propylene carbonate with a molar ratio of Zn(II)/Te(IV) = 10 and a low Te(IV) concentration; the film had a smooth and dense granular crystal morphology.     

Ultrafiltration of kraft cooking liquors from a continuous cooking process

Two cooking liquors and a black liquor were fractionated by ultrafiltration. The liquors were withdrawn from different stages in a kraft pulp mill employing continuous digestion. The ultrafiltration was performed at 90°C with two ceramic membranes with cut-offs of 5 kDa and 15 kDa. Only small differences in membrane performance were observed when concentrating the three liquors to 90% volume reduction. The average flux was 55 l/m² h for the 5 kDa membrane and about 115 l/m² h for the 15 kDa membrane. The concentration of lignin was on average 230 and 155 g/L in the retentate from the 5 kDa and 15 kDa cut-off membranes. The ash content was reduced from 37–40 g/g total dry solids to 20–30 g/g after ultrafiltration.     

The kinetics of the gaseous extraction of gallium from mica

The gaseous reduction of gallium in white mica has been studied using natural gas as the reducing gas. From a study at three temperatures, the initial extraction was observed to be linear with time and independent of particle size. The results suggest that delamination of the mica lattice is important. The measured activation energy for the loss of gallium from the white mica is 184 × 21 kJ mol^?1.     

The mechanism of manganese electrodeposition

The mechanism of manganese electrodeposition from a sulphate bath on to a stainless-steel substrate has been studied by using current efficiency data to resolve the totali-E curves. A simple, two-step electron transfer mechanism: $${\text{Mn}}^{{\text{ + + }}} + {\text{e}}\xrightarrow{{{\text{r}}{\text{.d}}{\text{.s}}}}{\text{Mn}}^{\text{ + }} $$ $${\text{Mn}}^{\text{ + }} + {\text{e}} \to {\text{Mn}}$$ is proposed to explain the following experimentally obtained parameters: cathodic and anodic transfer coefficients, reaction order and stoichiometric number. The mechanism also explains the effect of pH oni _o,Mn and on the corrosion currents.     

The direct adsorption of low concentration gallium from fly ash

This study is mainly focused on the direct adsorption of low concentration gallium from the feed solution in pre-desilication soda-lime sintering process from coal fly ash. The adsorption kinetics, mechanism, and the influence of impurities, cyclic times, and eluant content are systematically researched. Results showed that the adsorption capacity was 2.89 mg/g resin with gallium concentration of 50 mg/L. The adsorption mechanism could be explained by the interaction between the oxygen atoms and nitrogen atoms of amidoxime group. Gallium was eluted efficiently by NaOH and Na₂S mixed solution and the concentration could be reached to 2400 mg/L.     

克拉霉素结晶母液回收工艺研究

通过克拉霉素结晶母液回收工艺研究提高产品的回收率,文中采用了4步过程回收克拉霉素结晶母液中的产品,包括粗品分离、二次溶剂萃取和产品结晶过程。实验结果表明:粗品分离过程中,浓缩物和水质量比为2.5∶1,过滤温度40℃时克拉霉素收率最高;溶剂萃取过程中,采用浓缩萃取液与改变温度的方法可提高产品纯度;克拉霉素的总收率达到47.8%,产品中克拉霉素和6,11-O-双甲基红霉素质量比由粗品中的约1∶1提高至52∶1。克拉霉素总回收率得到提高,给工业化生产带来较高的经济效益。     

The electrodeposition of aluminium from molten aluminium chloride/sodium chloride

The electrodeposition of aluminium from an AlCl₃/NaCl melt (80 wt % purified A1C1₃, 20 wt % NaCl at 175°C) has been studied and conditions established for the production of good quality electroplate on steel. To obtain a coherent, dendrite-free plate at current densities up to 16 mA/cm², the presence of not less than about 0.07 wt % hydrogen chloride was found to be essential. Under these conditions the current efficiency was 85%. Continued plating resulted in a progressive increase in current efficiency up to practically 100% and a progressive deterioration in plate quality. Addition of more HCl at this stage restored the original conditions. These observations explain inconsistencies in previously reported values for current efficiency and maximum current density. The mechanism of the action of HCl was not established but it is suggested that it may have an action akin to chemical polishing by dissolving off the high spots on the already deposited aluminium. Alternatively, the electrolytic reduction of hydrogen preferentially on active sites may block these off and so prevent the build-up of aluminium dendrites.     

The effect of additives on zinc electrodeposition from deep eutectic solvents

The electrodeposition of metals using ionic liquids has received considerable attention during the last ten years. Recent developments have taken these novel electrolytes from laboratory to commercial scale. One of the factors limiting the development into practical plating systems is the understanding of how brighteners function. In this study we describe the addition of three polar additives and their effect upon the nucleation mechanism of zinc and the resultant morphology. It is shown that the structure of the zinc deposits is controlled by double layer properties and it is proposed that the brightening effect of ethylene diamine and ammonia are caused by their ability to inhibit the adsorption of chloride at the electrode surface. The deposition of most metals using ionic liquids results in apparently amorphous deposits, which tend to be actually nano-crystalline. The additives used in this study produce macro-crystalline deposits, which resemble those obtained from aqueous solutions.     

Lead electrodeposition from very alkaline media

The electrodeposition of lead from very alkaline media has been studied by cyclic voltammetry, chronoamperometry under stationary and convective conditions. Experimental parameters like lead concentration and temperature have been varied. From NaOH 6 M the metal deposition takes place at about −0.90 V versus SCE far from the hydrogen evolution reaction (HER) which is seen at −1.30 V, but both processes are favoured by the lead content increase and the NaOH concentration decrease. The analyses of the chronoamperometric responses support the view of a 3D growth and suggest a substantial influence of lead concentration on the type of nucleation. Progressive nucleation is observed for the deposition from solutions with low content in lead but as this concentration increases a tendency towards instantaneous nucleation is revealed. The voltammetry with the rotating platinum disc electrode has confirmed that the lead electrodeposition is a mass transfer controlled process, and also allowed the estimation of diffusion coefficients.     

Barrel zinc electrodeposition from alkaline solution

This paper discusses the influence of electrochemical parameters on the concentration–time relationship in an electrolytic zinc deposition reactor using a three-dimensional electrode. The dynamic behaviour of a zinc plating unit is obtained from the fundamental material balance. Two stages are considered: (i) the batch electrolytic reactor, and (ii) the electrolyser surrounded by rinses (i.e., contribution of drag-out). This theoretical approach shows that good control of the operating parameters helps stabilise the zinc electrolyte and, therefore, the properties of the zinc deposits. The aim of the experiments is to investigate, in a statistically designed test program, the effects of the composition of the alkaline zinc electrolyte on cathode efficiency and on the morphologies/textures of the deposits.     

Model of nickel electrodeposition from acidic medium

A step-wise computer model is presented for simultaneous deposition of nickel and nickel hydroxide in aqueous solutions. In acidic solutions ({pH} 1), the potentiostatic current-time transient response on glassy carbon or titanium was analysed with respect to nucleation and radial growth mechanism. pH changes influence the current-time response greatly. A marked maximum in the current transient appears for slightly acidic solutions ({pH} 4.5) and a consecutive decrease in the deposition current density at long times is obtained. This behaviour is attributed to early precipitation of nickel hydroxide due to a local pH increase at the cathode surface.     

电子废弃物回收镓技术的研究进展

含镓电子废弃物通常可分为废弃电子产品及其生产过程中产生的含镓废料两类,由于伴生重金属、易燃有机物等有害物质而具有环境和资源的双重属性,其资源循环近年来受到广泛关注.镓在电子废弃物中主要以化合物形式赋存,具有伴生元素多、物理化学性质稳定等特征.本工作系统梳理了含镓电子废弃物回收处理现状,总结了湿法冶金、火法冶金及生物冶金...     

Investigations on electrodeposition of nickel from dimethylsulfoxide

Process of cathodic deposition of nickel mainly from Ni(BF₄)₂ solution in DMSO has been investigated using various experimental techniques. It has been found that this process is complicated. The collected experimental data indicate that passivation of fresh cathodic layer of Ni by chemisorption of DMSO molecules takes place. By basing on the rde methods the values of αn_m = 0.4 (± 0.05) and k_fh = f(E_c) have been estimated.