Roland Kammel

Thiourea leaching of silver from mechanically activated tetrahedrite

Abstract The thiourea leaching of silver from a tetrahedrite concentrate mechanically activated in a planetary mill or an attritor was studied. It was found that the two types of equipment gave rise to different rates of new surface formation and of crystal structure disordering. The rate of thiourea leaching of silver from tetrahedrite (Cu,Ag)10(Zn,Fe)2(Sb,As)4S13 is a structure-sensitive quantity, while the dependence of the rate constant of leaching on the empirical coefficient S A (1 − R) (SA = specific surface, R = disordering of tetrahedrite structure) exhibits a linear character with equal slope for both types of mills. The results are also of prognostic character because they enable us to propose suitable equipment for intensive grinding depending on the demand for fineness or reactivity of the solid substances.

Leaching of antimony and mercury from mechanically activated tetrahedrite Cu12Sb4S13

Abstract In this study the physico-chemical transformations and leachability of antimony and mercury from tetrahedrite concentrate mechanically activated by intensive grinding in a planetary mill were investigated. It has appeared that the leaching of antimony and mercury from tetrahedrite in alkaline solution of sulphide solution is a structure-sensitive reaction. The temperature dependence of both reactions investigated in the temperature interval 298–363 K has shown that these reactions do not involve any change in mechanism. The experimental activation energies found in this connection were E = 7 kJ mol −1 for the leaching of mercury and E = 33 kJ mol −1 for the leaching of antimony.

Leaching of chalcopyrite concentrate with ferric chloride

Abstract In this study the kinetic leaching characteristics of chalcopyrite concentrate from Cuba (32.3% Cu) were investigated with granularities − 315 + 200 μm as delivered. The value of the apparent activation energy was determined to EA = 55 ± 5 kJ/mol, which is in agreement with published results. Microscopic and X-ray diffractometric investigations have confirmed that by measurement of real structure changes the assumed reaction chemism and the mechanism of chalcopyrite leaching can be observed.

Leaching and dissolution of a pentlandite concentrate pretreated by mechanical activation

Abstract This paper describes the properties and leaching behaviour of a pentlandite concentrate mechanically activated by grinding in an attritor (stirring ball mill) in H2O for 15–60 min. It appears that mechanical activation brings about an increase in specific surface area and a decrease in the content of crystalline phase of the mineral components pentlandite (Fe,Ni)9S8, chalcopyrite CuFeS2 and pyrite FeS2. These transformations are accompanied by mechano-chemical surface oxidation of individual minerals and the formation of water-soluble Ni, Cu and Co compounds. The process of mechanical activation in water and subsequent leaching in an acid solution (Fe2(SO4)3) proceeds in two steps. In the first step (dissolution in H2O), 46% of Ni, 29% of Cu and 29% of Co dissolve; and the rest can be extracted in the second step (leaching in Fe2(SO4)3 solution). Mechanical activation affects the selectivity of extraction of individual minerals.

Zinc electrowinning from flue dusts at a secondary copper smelter and connected adhesion problems of the metal deposits

Abstract The secondary copper smelter “Metallhutte Carl Fahlbusch” (MCF), Rastatt, Federal Republic of Germany is discussed, with particular consideration of the MCF zinc electrowinning process from low-grade, chloride-containing flue dusts. The investigations performed were focussed on the adhesion of zinc deposits on the aluminium cathodes. With laboratory tests using the tankhouse electrolyte and an apparatus for measuring the adhesion force, the influence of the electrolyte impurities lead, cadmium, cobalt, nickel, tin and antimony on the adhesion behaviour and on the current efficiency have been determined. Field tests to affect the adhesion of the zinc deposits on aluminium cathodes by dip pretreatment of the cathodes with glue or sodium resinate reveal that with only small sodium resinate additions in the dipping bath better stripping can be achieved.

Surface Roughness Measurement with Speckle Intensity Distribution Detected Using a Linear Image-Sensor

An experimental study is made of the far-field intensity distribution of speckles caused by rough surface. The maximum intensity of speckles formed by optical Fourier transform is detected with a linear image-sensor (28 µm×28 µm×512). The ratio of the maximum intensity to the total power of the scattered light is found to be a scale for the roughness of samples. The method is applicable to the measurement of surface roughness, independent of correlation length and reflectance variation caused by contamination of surface.

Electrolytic Recovery of Precious Metals From Dilute Solutions

Electrolytic recovery of gold and silver from dilute solutions was first applied nearly 100 years ago. Compared with other recovery techniques, electrolytic treatment offers several advantages. But to achieve high space-time yields, special construction of electrolytic cells for improved mass transfer is necessary. Extended cathode surface areas and vigorous agitation are important features. Gold and silver recovery by use of newly developed electrolytic cell construction—rotating tubular bed reactor and impact rod reactor—has been described. Calculations based on industrial application over several years confirm that electrolytic recovery of precious metals from dilute solutions has been very economical.

Preliminary study of hydrometallurgical refining of MG-silicon with attrition grinding

Abstract We report on our studies to remove impurities such as Fe, Ca, Al, etc., from metallurgical grade silicon MG-Si using a combination of attrition grinding and leaching. The study was divided into two parts. First, impure MG-Si was leached under different conditions in a closed leaching vessel. Second, fine MG-Si was ground with an attritor using different types of grinding balls, grinding media and grinding time. The slurries were then leached again in a leaching vessel. Sulfuric acid reduced the carbon content to some extent and attrition grinding by glass balls plus HCl, combined with leaching by HCl, drastically lowered impurities such as Fe, Al and Ca to around 10 ppm in one hour. This is a much shorter leaching time than has been attained previously. We also found that a particle size of about 1 μm provides the optimum effects on hydrometallurgical refining of MG-Si. Hydrometallurgical refining of MG-Si combined with attrition grinding saves leaching time and allows the use of normal acids such as HCl rather than the use of the caustic and more dangerous HF acid.

Metal Recovery from Dilute Aqueous Solutions by Various Electrochemical Reactors

Interest in the recovery of metals from dilute aqueous solutions is steadily increasing because of environmental concerns and potential economic rewards. Since conventional electrowinning cell systems with parallel plate electrodes are unsuitable for an efficient and economic treatment of effluents, many novel electrolytic methods with two-, semithree- and three-dimensional electrodes have been developed and few cell designs are already successfully applied on an industrial scale. The most important characteristic of these cell systems to ensure high current efficiencies and high production rates is improved mass transfer by use of extended cathode surfaces and vigorous agitation of the electrolyte. In competition with other effluent treatment methods such as adsorption, evaporation, precipitation, cementation, ion exchange, liquid-liquid extraction and reverse osmosis, the electrolytic processes offer the possibility of recovering the metal values from dilute solutions as a marketable metal product in a one step process. This review is focused on industrial applied cell designs and their special field of application. Their economics and cost savings in comparison with conventional treatment techniques are outlined and discussed.

Refining of crude nickel sulphate obtained from copper electrolyte

Abstract A new method of crude nickel sulphate refining for the Copper Smelter at Krompachy (Slovak Republic) was studied. The crude nickel sulphate removed from the copper electrolyte in the tankhouse contains iron, copper, zinc, and cobalt as impurities, mostly in the form of sulphates. The new method used for the removal of impurities comprises a gradual oxidation followed by selective hydrolytic precipitation of the impurities. The results of the investigation indicate that individual hydroxides will precipitate from the solution with increasing pH in the following sequence: Co(OH) 3 →Fe(OH) 3 →Cu(OH) 2 →Zn(OH) 2 →Pb(OH) 2 →Fe(OH) 2 →Co(OH) 2 . Due to the high concentration in the solution, nickel precipitates at lower pH values. Strict control of the pH therefore ensure that the other impurities in the crude nickel sulphate solution are precipitated before the nickel.