Part Of Cobalt Research Articles

Talvivaara mining company – From a project to a mine

The latest commercial application of bioleaching, and the first in Europe, is the Talvivaara Sotkamo Mine in North-Eastern Finland. The ore is low grade black schist, and contains pentlandite, pyrrhotite, chalcopyrite, sphalerite and pyrite as the main sulphide minerals. The ore and the possible utilization of the deposits have been extensively studied for over 20years. Bioheapleaching technology was chosen for the extraction of nickel from the ore based on its favourable capital and operational costs and the good performance data obtained in a large on-site pilot trial. Mining was started in Sotkamo in April 2008 and building of the industrial scale bioheap in August 2008. The first shipment of nickel sulphide product was delivered to the customer in February 2009.The mining method at Talvivaara is open pit mining, after which the ore is crushed and screened, agglomerated and finally stacked on the primary heap pad. Air is supplied to the stacked ore with low pressure fans through aeration piping inside the heap. The heap is irrigated from the top with acidic leaching solution, and the solution is collected from the bottom of the heap. A 10% side flow is taken for metals recovery and the rest of the solution is recycled back to the irrigation of the heap. After approximately 13–14months of bioleaching on the primary pad, anticipated recoveries are about 70% for nickel and 60% for zinc. The leached ore is then reclaimed and re-stacked onto the secondary heap pad. In secondary leaching the rest of nickel and zinc and part of cobalt and copper will be leached. The anticipated total recoveries after both primary and secondary leaching are 85% for nickel, 80% for zinc, and 50% for both copper and cobalt. In the metals recovery process, the metals are precipitated from the pregnant leaching solution using gaseous hydrogen sulphide. The resulting products are intermediates which are transported for further processing in refineries operated by the company’s customers.

CO hydrogenation and methane activation over Pd–Co/SiO 2 catalysts prepared by sol/gel method

Silica supported cobalt, palladium and cobalt–palladium bimetallic catalysts were prepared by sol/gel technique and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES). The CO hydrogenation and low temperature methane activation under non-oxidative condition were used as test reactions. It was established that, in contrast to other Pd–Co systems, bimetallic particles were not formed, only a part of cobalt was reduced in the presence of palladium and the cobalt was segregated to the catalyst surface. In the CO hydrogenation over a catalyst with the ratio of Co/Pd=2, a synergism was observed, while over cobalt and palladium catalysts alone lower activities were measured. Over pure cobalt sample, which has a limited reducibility, only short chain hydrocarbons, mainly alkenes, are formed, whereas in the presence of palladium (sites for enhanced hydrogen activation), the amount of alkanes increased. The limited reducibility of the cobalt was explained by the small particle size due to the preparation technique. Palladium acts in the bimetallic system not only as a component, facilitating cobalt reduction, but as a source of hydrogen participating in the reaction.

A study of the cobalt sites in cobalt and iron molybdate catalysts by emission Mössbauer spectroscopy

Molybdates samples containing 74MBq (2mCi) of cobalt 57 have been studied by emission Mossbauer spectroscopy. Spectra of57CoMoO4 exhibited the three usual Fe2+ doublets corresponding to α and β ferrous phases, and two Fe3+ doublets accounting for about one third of the absorption area. The Co2+ sites of β57CoMoO4 phase exhibit higher quadrupole splittings, i.e. are more dissymmetrical than Fe2+ sites of βFeMoO4 phase. Cobalt and iron molybdates Fex57Co1−xMoO4 provided spectra where only one Fe3+ doublet appeared and occupied less than 7% of the spectral area. It is concluded that a part of cobalt was present in57CoMoO4 as Co3+.

Correlation of catalytic activity with the amount of sulphhydryl groups in molybdenum hydrodesulphurization catalysts

The adsorption of silver ions from a pyridine solution of silver nitrate onto nine commercial sulphided hydrodesulphurization catalysts was studied. The amount of sulphhydryl groups SH was determined on the basis of the amount of protons liberated in this reaction. The reaction of catalysts with silver ions was compared with their activity in thiophene hydrodesulphurization under pressure. A dependence was found between the amount of silver ions adsorbed and the rate constant of thiophene hydrodesulphurization. For cobalt-molybdenum catalysts, a relationship exists between this constant and the amount of sulphhydryl groups. It was ascertained that the catalysts which are most active in the thiophene desulphurization probably contain, in sulphided state, a part of cobalt (nickel) in the form of sulphides.

市販歯科用合金について (I)

During and after the War, noble metals such as gold and platinum were used few amount on account of controll of the government and economical poverty of the people. So, the investigation on substitutes for gold alloy has widely developed and various kinds of substitutive dental alloys have been produced.In this report, the results on chemical analysis, micro-structure and Vickers hardness of these substitutes are shown and brief discussion on these alloys is stated from the standpoint of metallography.The results on silver alloys are shown in Table 1. The defect of silver alloys is to be tarnished by sulpher ion. It is well known that addition of palladium and gold prevent this, hewever most of alloys in the market increase their resistance to corrosion by addition of cadmium, zinc and tin. Alloys which contain about 80 % silver are not sufficient to prevent tarnishing, but have comparatively good ductility and high melting point, so they are directed for use as cast crown, swaged plate, etc. Alloys contain 60-70 % silver have good corrosion resistance and are used for cast inlay. Ag-Cu alloys show age-hardening characteristic by quenching and tempering, however maker of these alloys do not, direct to utilize this phenomena. It is doubtful to use silver alloy which contains 27.63 % copper for clasp and bur. For this alloy has eutectic structure and is known as brazing solder.Cu-Zn-Ni, Cu-Sn-Ni and Cu-Zn alloys are found in the market. (Table 2) They are used for only casting. Cu-Ni-Zn alloy contains more zinc than usual nickel silver to lower the melting temperature. These alloys have some defects, for instance, comparatively high melting point, somewhat poor resistance to corrosion and evaporation of zinc during melting. The evaporation of zink increase the melting point and decrease the hardness and corrosion-resistance. These alloys have dendritic structure when they are cast by investment process. (Photo. 3-5)The results on Sn-Sb alloy are shown in Table 3. This alloy has very low melting temperature, so care must be taken to prevent the growth of primary phase. To get fine structure, it is necessary to cool down the mould to room temperature. (Photo. 6-8)As wrought alloys, Ni-Cr, 18-8 stainless steel and Co-Cr alloys are in the market and chemical compositions of these alloys are shown in Table 4, 5 and 6 respectively. Ni-Cr alloy sheets are widely used in this country for crown. Co-Cr alloy is succeedingly used for precise casting. The effort to use this alloy for wrought wire produced the composition of Co-Cr-Fe-Ni system shown in Table 6. A part of cobalt is replaced by nickel and iron to increase their workability. In ferrous alloys, carbon which is contained in material as impurity, forms carbide by heat-treatment and intergranular corrosion takes place for the reason of this carbide. So that, care must be paid to the heat treatment.