镍白铜废料中铜的低电流密度电解回收

对镍白铜合金废料进行直接低电流密度电解回收,考察了电解液温度、电流密度、明胶浓度对阴极铜纯度和表面质量的影响. 结果表明,一定范围内电解液温度升高阴极过电势降低,铜离子扩散速度加快,阴极表面铜离子缺乏程度缓和,阴极铜结晶细化;在Cu2+浓度45 g/L、H2SO4浓度180 g/L、电流密度100 A/m2的条件下,48 h内电流密度小于极限电流密度的0.1倍,电解区域处于塔费尔控制区,阴极铜产品平整光滑;控制明胶浓度40 mg/L、电解液温度60℃和电流密度100 A/m2时,镍白铜废料直接电解所得阴极铜纯度达99.98%,表面平整韧性良好,阳极残极率为17%~19%,铜回收率达98.6%.     

Electrodeposition at rotating cathodes from acidified copper sulphate solution

The variation of the relationship between polarisation and current density at a rotating copper cathode in an electrolyte of copper sulphate and sulphuric acid has been observed under conditions and concentrations similar to those employed in the plating industry, and during the formation of thick deposits. The effect of the following parameters was studied: time of electrolysis, agitation, temperature and composition of electrolyte, and the consequent effects upon the structure of the resulting deposits were noted. The possible effects of the co-deposition of hydrogen at the cathode is discussed in relation to the structure of the copper at high current density.     

Recovery of nickel powder from copper bleed electrolyte of an Indian copper smelter by electrolysis

When nickel concentration increases in the copper sulphate electrolyte during electrolysis, it starts electrodepositing on the copper cathode thereby affecting the purity of the copper. In order to produce high quality copper cathodes with less than 1 ppm Ni, it became necessary to bleed-off large volumes of foul electrolyte contaminated with nickel and other impurities. The study reported in this paper was part of the effort aimed at devising a cost effective and an ecofriendly method for the production of value added powders from a waste stream, for P/M application. A part of copper salts and regenerated acid was used back into the system. As discussed in our paper on copper recovery from copper bleed stream (CBS), a process involving decopperisation and crystallisation-solvent extraction (SX) separation-electrowinning (EW) has been attempted as an alternative to the conventional process. Optimum conditions for nickel recovery from this type of solution have been investigated through a series of experiments carried out in a rectangular electrolytic bath with SS as cathode and Pb-Sb as anode. A quantitative and selective recovery was found for nickel deposition under suitable conditions. The purity of the electrolytic nickel powders so produced was found to be 99.89%. The compact density of the annealed nickel powder was 7.72 g/cc. Other properties of the nickel powders such as flow-ability, particle size, etc. were also evaluated to assess its suitability for its use in P/M applications.     

高浓度含铜电镀废水膜电解处理与回用

随着电镀行业的发展，电镀废水排放造成的污染问题一直困扰着研究者。而针对其中高浓度含铜电镀废水少污染、可回收的目标，开发了单膜双室膜电解法处理并回收铜的新工艺，本实验研究了其运行方式、回收效果与机理并对回收的产物进行表征。在一个电解槽内阴阳两极之间放入一张阴离子交换膜，研究了初始Cu²⁺浓度、电流密度、pH、极板间距、温度和添加剂等运行参数对铜回收率和能耗的影响。在Cu²⁺初始浓度50g/L，阴极板电流密度400A/m²，温度40℃，极板间距30mm，阴极室pH=6.5，添加1g/L硝酸铵的最优工况下，测得铜回收率可以达到96.1%，电流效率超过70%，并且反应能耗为5737kWh/t。同时通过表征分析在最佳工艺条件下电解回收的铜，发现其颗粒较小、大小均匀、棱角分明，且其纯度高，具有较高的经济价值。     

High-speed jet electrodeposition and microstructure of nanocrystalline Ni-Co alloys

The jet electrodeposition from watts baths with a device of electrolyte jet was carried out to prepare nano-crystalline cobalt-nickel alloys. The influence of the concentration of Co²⁺ ions in the electrolyte and electrolysis parameters, such as the cathodic current density, the temperature as well as the electrolyte jet speed, on the chemistry and microstructure of Ni-Co-deposit alloys were investigated. Experimental results indicated that increasing the Co²⁺ ions concentration in the bath, the electrolyte jet speed and decreasing of the cathodic current density and decrease of the electrolyte temperature all results in an increase of cobalt content in the alloy. Detailed microstructure changes upon the changes of alloy composition and experimental conditions were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD results show the Ni-Co solid solution was formed through the jet electrodeposition. Phase constitution of solid solution changes progressively under different electrolyte concentration. Alloys with low Co concentration exhibit single phase of face-centered cubic (fcc) structure; The Co concentration over 60.39 wt.%, the alloys are composed of face-centered cubic (fcc) phase and hexagonal close-packed (hcp) phase. Furthermore, the formation of the nanostructured Ni-Co alloy deposit is investigated. Increasing the Co²⁺ ions concentration in the bath, the cathodic current density, the electrolyte temperature and the electrolyte jet speed all result in the finer grains in the deposits. Additives such as saccharin in the electrolyte also favor the formation of the finer grains in the alloy deposits.     

Electrochemical synthesis of cupric oxide powder Part II: Process conditions

Electrosynthesis of cupric oxide powder was carried out on a laboratory scale in an electrochemical cell under various experimental conditions. The electrolysis was appraised in terms of the particle size of the cupric oxide product and the anodic dissolution of the copper electrode. Using a previously determined pH value of 7.50, the other optimum electrolysis operating conditions established were a current density of 4000Am–2, temperature of 353K, and Na2SO4 concentration of 0.5m. The optimum values of current efficiency, cell voltage and specific energy consumption for the electrochemical synthesis of cupric oxide powder were determined.     

Design and performance of a laboratory cell for determination of current efficiency in the electrowinning of aluminium

A new and improved laboratory cell has been specifically designed for determination of current efficiency (CE) as a function of isolated variable parameters in the Hall-Heroult aluminium electrolysis process. The anode is designed to give enhanced and reproducible bubble induced electrolyte convection, while the wettable cathode gives a well defined cathode area, and thus a uniform cathodic current density. Results are given of CE and cathode polarization as functions of cathodic current density, and of CE as a function of interpolar distance. Experiments show reproducible and high values of CE, and low and consistent values of cathode polarization. The CE does not vary for interpolar distances between 10 and 40 mm in the present cell. The cell is well suited for experimental determination of CE as function of electrolyte composition, including impurity concentrations, temperature and current density.     

Zinc barrel electroplating using low cyanide electrolytes

The influence of plating conditions on the cathode efficiency of zinc barrel electroplating and the quality of deposited layers for low cyanide electrolytes is analysed. The investigations are carried out using factorial design methodology. The first part of the study shows how electrolyte components, such as brightening agent, sodium carbonate concentration, sodium hydroxide concentration, sodium cyanide concentration and zinc metal content, influence cathode efficiency and the morphology and the texture of the zinc electrodeposits. A mathematical model that fits experimental data is suggested and the pseudo three-dimensional plot of yield as a function of electrolyte composition for three significant component mixtures, brightening agent, sodium cyanide concentration and zinc metal content, is represented. The second part of the study shows how varying six process parameters influences current efficiency and metal thickness distribution. For the range studied, efficiency is affected by workload volume, current density, perforation and part size, but not by rotation speed and quantity of charge.     

脉冲电解法制备金属镍的工艺研究

研究了高电流密度下影响脉冲电解制备镍的因素,得到最佳工艺条件为:电解液中支持电解质硫酸氨用量为35～45g·L-1,阴阳极的极间距范围在4～6cm之间,添加剂用量:氯离子3.0mg·L-1,尿素0.25mg·L-1,甘油0.5mg·L-1.并采用激光粒度分析仪和扫描电镜对电解产品的粒度分布、粒径和形貌特征进行观察和分析...     

硫酸铬电解氧化反应的研究

为了制备间接电氧化合成菲醌的氧化剂Cr2O72-,对硫酸铬电解氧化反应进行了实验研究,考察了电流密度、电解时间、反应温度及硫酸含量对电解效率的影响。通过实验得出:在隔膜电解槽中,采用Pb作阴极,Pb-PbO2作阳极,Cr3 电氧化的最佳条件是反应时间4 h,电解液中硫酸浓度30%,电流密度67 mA/cm2,所得Cr2O72-收率为95%左右。     

Synthesis of Gadolinium-Doped Ceria Powders by Electrolysis of Aqueous Solutions

A gadolinium-doped ceria powder was produced by electrolysis of an aqueous solution containing Ce³⁺ and Gd³⁺ ions using direct and alternating current at 4–10 V of applied voltage between two platinum wire electrodes (anode and cathode). The powders produced were identified as a gadolinium-doped ceria solid solution by X-ray diffraction and chemical analysis. Large porous particles 60–70 μm in size were produced under a direct current field for 15 min. On the other hand, nanoparticles 40–250 nm in size were produced for 6–12 h of electrolysis using alternating current below 20 Hz of frequency. No particles were formed in the high frequency range from 100 Hz to 1 MHz. The nucleation and growth rates of the particles depended on the frequency of the alternating current and electrolysis time applied. The Gd₂O₃/CeO₂ ratio of the particles formed with alternating current was lower than that of the starting solution.     

A study of copper electrowinning parameters using a statistically designed methodology

This study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A m^–2), copper concentration (25 and 65 g l^–1), and temperature (40 and 60 °C). Pure, synthetic electrolyte with a constant acid concentration of 180 g l^–1 was used. The designed study produced a linear relationship where the independent variables of current density, copper concentration, temperature and their interactions were found to be statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to incorporate into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.     

Influence of cathodic overpotential on grain size in nanocrystalline nickel deposition on rotating cylinder electrodes

Nanocrystalline (nc) nickel was electrodeposited using rotating cylindrical electrodes (RCD) from a Watt’s bath containing saccharin. The effects of cathode rotation speed and saccharin concentration on the cathodic overpotential and grain size were studied. The grain sizes are presented as a function of the cathodic overpotential. All reported cathodic overpotentials were corrected for ohmic overpotentials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to determine the deposit grain size. In addition, the influences of cathode rotation speed and current density on the morphology of nanocrystalline nickel were observed by scanning electron microscopy (SEM).     

电铸铜制备小直径薄壁回转体零件

采用3D打印的圆柱体作为芯模电铸铜,得到小直径薄壁回转体零件。配方和工艺条件为:CuSO4·5H2O 200 g/L,浓硫酸60 g/L,Cl-0.05 g/L,pH 1,温度26℃,极间距3 cm,电流密度2~8 A/dm2,阴极表面线速率3.14~12.56 mm/s。研究了电流密度和阴极表面线速率对电铸铜表面形貌和显微硬度的影响。随电流密度或阴极表面线速率增大,电铸铜的晶粒得到有效细化,组织更均匀、致密,显微硬度先增大后减小。电流密度为4A/dm2,阴极表面线速率为9.42 mm/s时,电铸铜的表面形貌最好,显微硬度最高,所得回转体零件表面光滑、平整,厚度均匀。     

电化学方法处理酸性艳兰6B染料废水的研究

采用钛网作为阳极,钛网为阴极,对酸性艳兰6B模拟染料废水进行了实验研究,探讨了电解时间、电解质浓度、电流密度以及进水浓度对酸性艳兰6B脱色效率的影响。结果表明:增加电流密度,提高电解质浓度,延长反应时间有利于酸性艳兰6B色度的脱除,对于含有100 mg/L的酸性艳兰6B溶液,电解质NaCl的质量浓度为20.0 g/L,电流密度为2.5 A/dm2,电解时间25 min,溶液的脱色率达到93.75%。     

Electrochemical reduction of ethylpicolinate: Competitive aspects of pyridine nucleus hydrogenation and ester reduction

Electrolyses of ethylpicolinate in aqueous sulfuric acid solutions were performed on a lead cathode in galvanostatic mode. The reduction of the ester function was in competition with that of the pyridine nucleus. Study of the change in solution composition with time during electrolysis allowed evaluation of the influence of parameters such as acidity, current density, initial concentration of ethylpicolinate and temperature, on the competing formation of the different electrolysis products. Parameter values were chosen for synthesis of 2-hydroxymethylpyridine.     

Spray Drying of Mannitol as a Drug Carrier—The Impact of Process Parameters on Product Properties

Powders intended for the use in dry powder inhalers have to fulfill specific product properties, which must be closely controlled in order to ensure reproducible and efficient dosing. Spray drying is an ideal technique for the preparation of such powders for several reasons. The aim of this work was to investigate the influence of spray-drying process parameters on relevant product properties, namely, surface topography, size, breaking strength, and polymorphism of mannitol carrier particles intended for the use in dry powder inhalers. In order to address this question, a full-factorial design with four factors at two levels was used. The four factors were feed concentration (10 and 20% [w/w]), gas heater temperature (170 and 190°C), feed rate (10 and 20 L/h), and atomizer rotation speed (6,300 and 8,100 rpm). The liquid spray was carefully analyzed to better understand the dependence of the particle size of the final product on the former droplet size. High gas heater temperatures and low feed rates, corresponding to high outlet temperatures of the dryer (96–98°C), led to smoother particles with surfaces consisting of smaller crystals compared to those achieved at low outlet temperatures (74–75°C), due to lower gas heater temperatures and higher feed rates. A high solution concentration of the feed also resulted in the formation of comparably rougher surfaces than a low feed concentration. Spray-dried particles showed a volume-weighted mean particle size of 71.4–90.0 µm and narrow particle size distributions. The mean particle size was influenced by the atomizer rotation speed and feed concentration. Higher rotation speeds and lower feed concentrations resulted in smaller particles. Breaking strength of the dried particles was significantly influenced by gas heater temperature and feed rate. High gas heater temperatures increased the breaking strength, whereas high feed rates decreased it. No influence of the process parameters on the polymorphism was observed. All products were crystalline, consisting of at least 96.9% of mannitol crystal modification I.     

Morphologies of electrochemically formed copper powder particles and their dependence on the quantity of evolved hydrogen

Copper powder particles formed by electrolysis under different quantities of evolved hydrogen were analyzed using the scanning electron microscopy (SEM) technique. It was found that the structure of the powder particles strongly depended on the quantity of evolved hydrogen — that is, two types of powder particles were formed, depending on the quantity of evolved hydrogen. One type of particle was formed during the electrodeposition of copper when the quantity of evolved hydrogen was insufficient to change the hydrodynamic conditions in the near-electrode layer. This particle type comprised dendrites constructed of corncob-like structures as the basic element. The other type of particle was cauliflower-like and was formed when the quantity of evolved hydrogen was sufficient to change the hydrodynamic conditions in the near-electrode layer. However, both types of particle consisted of agglomerates of copper grains. The only difference lay in the size of the copper grains of which the agglomerates were constituted. The size of the grains was a function of the electrodeposition overpotential and, consequently, the quantity of evolved hydrogen, with a tendency to attain a steady value when the electrodeposition overpotential was increased.     

Electrochemical evaluation of copper deposition with gas sparging

The influence of gas sparging during copper electrolysis was studied using standard electrochemical techniques. The polarization behaviour of acid copper electrolytes was determined in the presence and absence of gas sparging on vertical electrodes. Tracer ion techniques were employed to determine the effect of gas sparging and forced circulation of the electrolyte on the mass transfer characteristics of the system. In addition to the potentiodynamic scans, 3-h copper deposits were produced for morphology and orientation studies. The effect of current density and temperature on deposition were also studied. The polarization experiments have shown that a mass transfer component becomes evident at about 40% of the limiting current density at which point the deposit becomes noticeably rougher.