Zinc Recovery via the Flame Reactor Process

A major objective of the zinc industry for the 1990s will be to maintain high zinc recovery while eliminating the disposal of copious quantities of hazardous iron residues. The flame reactor process has demonstrated the potential of meeting this objective by either treating the residues or smelting zinc directly. The process has been proven commercially viable for treating flue dusts generated during electric arc furnace steelmaking. Zinc, lead and cadmium are recovered from the dust as a crude oxide for recycle while a nonhazardous slag is produced for sale. Similar products are efficiently produced from electrolytic zinc plant neutral leach and iron precipitation residues. In addition, the reactor shows promise of fulfilling its original objective of being a low-energy primary zinc smelter by fuming and condensing zinc from roasted concentrates.     

Cadmium practice at Great Falls

Cadmium metal, for which the demand has increased many fold in the past several years, is a byproduct of zinc electrolysis. Here is presented the story of cadmium recovery and production in the electrolytic zinc plant of the Anaconda Co.’s Great Falls plant.     

Sb2O3在硫酸锌溶液净化除钴过程中的机理

Ｃｏ－Ｓｂ－Ｈ２Ｏ系电位－ｐＨ图表明，在锌粉置换除钴过程中，锑与钴形成金属间化合物，从而提高了锌粉置换除钴的热力学推动力。扫描电镜观察及Ｘ射线衍射结果表明，锑与镍和钴的存在形式相同，进一步说明钴与锑形成金属间化合物，而锌则以碱式硫酸锌、氧化锌和金属锌的形式存在。     

Kinetics of zinc sulfide concentrate direct leaching in pilot plant scale and development of semi-empirical model

The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined. All tests were carried out in the pilot plant. To allow the execution of hydrostatic pressure condition, the slurry with ferrous sulfate and sulfuric acid solution was filled into a vertical tube (9 m in height) and air was blown from the bottom of the reactor. The effects of initial acid concentration, temperature, particle size, initial zinc sulfate concentration, pulp density and the concentration of Fe on the leaching kinetics were investigated. Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinking core model (SCM). This process was controlled by a chemical reaction with the apparent activation energy of 49.7 kJ/mol. Furthermore, a semi-empirical equation is obtained, showing that the order of the iron, sulfuric acid and zinc sulfate concentrations and particle radius are 0.982, 0.189, ?0.097 and ?0.992, respectively. Analysis of the unreacted and reacted sulfide particles by SEM–EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lower than 60% Zn conversion and lixiviant in the face with sphalerite particles.     

Treatment of cadmium dust with two-stage leaching process

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Acid Leaching Extraction of Ga and Ge

The U.S. Bureau of Mines recently investigated sulfuric acid leaching to extract gallium and germanium from a zinc processing residue containing 0.32% Ga and 0.46% Ge. These metals can be extracted by leaching with sulfuric acid alone or by leaching with sulfuric acid and sulfur dioxide. A low temperature roasting treatment also aids in extracting 20% more germanium. A high percentage of the residue’s remaining zinc and cadmium is extracted using either technique.     

从铜镉渣中回收镉的试验研究

本文介绍了从铜镉渣中回收镉的试验研究情况，采用酸浸-铜镉渣中和-锌粉除铜法处理铜镉渣，工艺简单合理，镉直收率高，有一定的推广价值。     

The atmospheric corrosion resistance of electrodeposited tin-cadmium and tin-zinc coatings on steel

Abstract

A study has been made of the corrosion-resisting properties of tin-cadmium and tin-zinc coatings on steel in which both laminar and alloy coatings have been tested using atmospheric exposure and accelerated tests. It is concluded that electrodeposited coatings of zinc on a tin substrate or zinc alone possess a greater resistance to atmospheric corrosion in an industrial atmosphere than equivalent coatings of cadmium on tin or tin on cadmium, or tin-zinc alloy coatings. The corrosion resistance of tin-zinc laminar coatings depends primarily on the amount of zinc present. Alloy coatings of tin-zinc and tin-cadmium generally possess similar corrosion resistance to those of the tin and cadmium laminar coatings. Under simulated marine conditions (A.R.E. Salt Droplet test) the corrosion resistance of coatings containing cadmium is superior to that of corresponding coatings containing zinc.     

Study on Extracting Low Concentration Cadmium from Zinc Hydrometallurgy System by Liquid Membrane Crystallizing Technique

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Crystallographic, optical and electrical properties of low zinc content cadmium zinc sulphide composite thin films for photovoltaic applications

In this paper a screen-printing method has been employed for the deposition of low zinc content cadmium zinc sulphide (Cd_0.9Zn_0.1S) composite thin films on ultra clean glass substrate. Cadmium sulphide, zinc sulphide and cadmium chloride have been used as the basic source material. With these basic source materials, the optimum conditions for preparing good quality screen-printed films have been found. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal) structure with strong preferential orientation of grains along the (1 0 1) direction. SEM/EDAX analysis confirms the formation of ternary compound. The optical band gap (E_g) of the films has been studied by using reflection spectra in wavelength range 350-600 nm. The DC conductivity of the films has been measured in vacuum by a two probe technique.     

Self-assembled flower-like microstructure in Zn1-xCdxO nanoparticles

The structural and optical characterization of cadmium-doped zinc oxide nanoparticles synthesized by precipitation method was studied. X-ray diffraction study confirmed the substitution of cadmium dopant without disturbing the basic wurtzite structure of zinc oxide. The average crystalline size, lattice constants and unit cell volume also increased up to 4% of cadmium doping. Energy gaps of the samples were determined from the ultraviolet-visible absorption spectrum as well as Tauc's plot which infers that the energy gap decreases with the increase of cadmium content. Fourier transformation infrared spectrum confirms the cadmium dopant through peak shifting from 485 to 563 cm^?1. Photoluminescence spectrum also defines the cadmium dopant by intensity increase. The broad Raman peak at 437 cm^?1 indicates that the wurtzite structure of zinc oxide is weakened by 5% cadmium doping. Field emission scanning electron microscope study also confirms the existence of particles in nanometer size and it indentifies the microstructure transformation from nanoparticles to jasmine flower-like structure on 5% cadmium doping.     

Influence of organic additives on the behaviour of zinc electroplating from alkaline cyanide-free electrolyte

Two similar polymeric organic compounds from the polyquaternium family were studied as levelling additives in an alkaline cyanide-free zinc plating electrolyte. One additive (LA) has amide bonds between its monomers and the other (LU) has urea unions in its chemical structure. Copper cementation on zinc and gas evolution during aging of the zinc coatings were used to evaluate the effect of the chemical structure of the organic additives on the characteristic deleterious aging process of the coatings when electrodeposited with LA. Scanning electron microscopy and X-ray diffraction were used to follow surface morphology and crystallographic modifications of the coatings during aging. Faster copper cementation kinetics, zinc whiskers growth, blistering of the coating and N₂, CH₄, CO₂ and H₂ evolution were observed during accelerated aging of the coatings when LA was used. The coatings produced with LU did not show any aging effect. These studies show the strong influence that subtle changes in the chemical structure of the organic additive may have on the performance of zinc coating during storage.     

Selective separation of copper and cadmium from zinc solutions by low current density electrolysis

Copper and cadmium ions were selectively separated from zinc sulphate aqueous solution or zinc ammonia/ammonium sulphate aqueous solution by low current density electrolysis.It was shown that the concentration of cadmium ion in zinc sulphate solution decreased from 4.56 g/L to 0.18 g/L in an electrolysis time of 8.5 h,whilst it decreased from 5.16 g/L to lower than 0.005 g/L in zinc ammonia/ammonium sulphate aqueous solution.On the other hand,the deposition rate of copper was so low that it was difficult to...     

Zn-Ni合金渗层的组织结构及腐蚀性能EI北大核心CSCD

为改善传统渗锌层组织结构及腐蚀性能,采用甲酸镍和锌粉作为渗剂金属,通过机械能助渗法在Q235钢表面制备Zn-Ni合金渗层。结合扫描电镜(SEM)、EDS能谱和X射线衍射仪(XRD),分析Zn-Ni合金渗层的表面、截面和断口形貌;利用极化曲线和电化学阻抗谱(EIS),表征Zn-Ni合金渗层在3.5%NaCl溶液中的电化学行为;通过中性盐雾试验测试Zn-Ni合金渗层的耐腐蚀性能。结果表明:制备得到Zn-Ni合金渗层的厚度为153μm;渗层主要由Γ(Fe_(11)Zn_(40))相、ζ(FeZn_(15))相和Ni_(2)Zn_(11)金属间化合物组成,渗层结合方式属于冶金结合;Zn-Ni渗层中性盐雾试验出现红锈的时间相比渗锌层延长240 h,自腐蚀电位从−1.222 V正移至−0.957 V,渗层电阻提高352Ω·cm^(2);Ni对改善渗层表面组织状态和提高渗层耐腐蚀性具有显著价值。通过添加甲酸镍制备的Zn-Ni合金渗层相比渗锌层组织结构和腐蚀性能得到明显改善。     

Inhibitoren der Korrosion 25(1) – Über die Rolle der Kationen in Neutralsalzen bei der Korrosion von Eisenwerkstoffen in Gegenwart von Sauerstoff

Corrosion inhibitors 25(1) – The role of the cation in a neutral salt in the corrosion of iron in the presence of oxygen The rate of uptake of oxygen, under standard conditions, in the corrosion of 500 mg DAB6 iron powder is dependent on the nature of the cation in a neutral salt (chloride). In the presence of alkali, quaternary ammonium, quaternary phosphonium and alkali-earth chlorides, the rate of oxygen uptake is comparable. With zinc, cadmium, nickel and cobalt chlorides a marked decrease in the oxygen uptake is observed between pH5 and pH7. This is probably due to a block in the cathodic area in the iron boundary layer through precipitation of the rather insoluble basic hydroxides of zinc, cadmium, nickel and cobalt.     

The ancient brass cementation processes revisited by extensive experimental simulation

Prior to the mastering of metallic zinc production in the mid-19th century, brass making in Europe was based on the so-called cementation process: within a more or less closed vessel, gaseous zinc is produced by the carbothermic reduction of zinc ore at around 1,000°C (±100°C), and simultaneously diffuses into metallic copper. Few ancient brass objects dated before the Industrial Revolution analyzed so far bear more than 30 wt.% zinc, so that this zinc content value has become a dating criterion for these artifacts. The systematic laboratory-scale experimental simulations of the ancient process presented here permit the multiple influences of temperature, isothermal treatment duration, and initial Zn/Cu ratio on the zinc content of the final products, and on the zinc recovery rates as well, to be investigated for the first time.     

Advances in Replacements for Cadmium Plating in Aerospace Applications

This paper examines some of the problems associated with the replacement of cadmium plating for the protection of aircraft components and fasteners manufactured from steel. It reviews the range of coatings which are available commercially and are currently being considered as alternatives to cadmium plating. Results of research being undertaken into the corrosion behaviour and galvanic compatibility of electrodeposited zinc alloy coatings and aluminium-magnesium alloy coatings are presented. Other aspects of coating performance are also considered including frictional properties, effects of coatings on fatigue strength, hydrogen embrittlement of steels and the repair of damaged coatings. It is concluded that although the corrosion performance of cadmium plating may be achieved with several coating systems, no one coating is likely to be acceptable as a replacement for cadmium for all aerospace applications.     

Cominco’s new sinter plant

A lead smelter treating a high proportion of hydrometallurgical zinc plant residues requires specialized technique of feed preparation to incorporate the residues with other feed into a pelletized form for sintering. The design and operation of such a plant at Trail, B. C., is described.     

Plating and Polishing

Laboratory tests were made to determine the behaviour of cadmium and zinc coatings at room temperature and at 60°C. in humid atmospheres in the presence and absence of various insulating materials. The results indicate that cadmium plating, particularly if chromate, should give adequate protection to steel components in electrical equipment in most conditions of exposure even when temperatures and relative humidities are high. Rather more attack may be expected if condensation occurs. In the presence of moisture and certain insulating materials, however, corrosion of cadmium plating can be greatly accelerated and a dangerous loose corrosion product may be formed. One potent accelerating agent was a sample of yellow insulating tape which evolved acid vapours and caused the formation of corrosion products containing propionates and butyrates. Vapours of the lower fatty acids were also found to increase considerably the corrosion of cadmium. A sample of phenol-formaldehyde resin also accelerated attack, but in this case alkaline vapours were evolved. The results obtained showed that zinc coatings were less resistant than cadmium coatings under the various conditions used. Attack of zinc coatings also was greatly accelerated by the lower fatty acids and by the vapours from the yellow tape and the phenol-formaldehyde resin.     

Electrodeposited zinc alloy coatings

This review examines the range of zinc alloy electrodeposited coatings that are available as finishes for continuous steel strip and also possible replacements for electroplated cadmium. Each system is described in terms of available electrolytes, physical properties and corrosion resistance. It is apparent that zinc-nickel, zinc-iron and zinc-cobalt are the most widely utilized, although zinc-manganese, which appears to have excellent corrosion resistance, is in all probability unavailable commercially. Zinc-tin is also discussed, being recognized as another possible replacement for cadmium.