Desempenho das metodologias convencionais de quantificacao de reservas<>9d\estudo de um deposito de niquel

Ten working-groups were formed for estimation of nickel ore reserves, associated to an ultrabasic body, at Ipanema, MG. Each group employed six methods: parallel sections, isolines, triangles, polygons, blocks and statistical method. The triangles method showed more variability, and the smallest dispersion was obtained by the polygons method; the other methods induced fluctuations in relation to the mean. Top and bottom ore irregularities produced difficulties in the performance of the parallel sections method. Different ways of application of isolines method also produced some variations. Excepting for few calculated data, the overall results are very close to 2 200 000 t or ore. -English summary

Metallurgical evaluation of a copper-based alloy for dental castings.

The present study was designed to evaluate the metallurgical properties of an experimental, low-cost copper-zinc-aluminum-nickel alloy for dental castings. Some specimens were subjected to heat treatment after induction casting. The extent of corrosion was determined by measuring weight loss of specimens stored in a sodium sulfite solution. In the as-cast specimens, tests demonstrated the presence of three phases: the first consisted of copper-zinc-aluminum, the second was similar but lower in copper and aluminum, and the third consisted of an intermetallic compound of manganese-nickel-phosphorus. After heat treatment, the first phase remained relatively constant, the second was converted to Cu3Al, and the third increased in volume. The weight loss from the as-cast specimens was eight times that of the heat-treated specimens. It was concluded that the heat treatment substantially changed the microstructure and improved the corrosion resistance of the experimental alloy.

Assessment of anaerobic sewage sludge quality for agricultural application after metal bioleaching

The effects of metal bioleaching on nutrient solubilization, especially nitrogen and phosphorous, from anaerobically-digested sewage sludge were investigated in this work. The assessment of the sanitary quality of the anaerobic sludge after bioleaching was also carried out by enumerating indicator (total coliforms, fecal coliforms, and fecal streptococci) and total heterotrophic bacteria. The experiments of bioleaching were performed using indigenous sulphur-oxidizing bacteria (Thiobacillus spp.) as inoculum and samples of anaerobically-digested sludge. Nitrogen and phosphorous solubilization from sewage sludge was assessed by measuring, respectively, the concentration of Total Kjeldahl Nitrogen, ammonia, nitrate/nitrite, and soluble and total phosphorous before and after the bioleaching assays. At the end of the experiment, after 4 days of incubation (final pH of 1.4), the following metal solubilization yields were obtained: zinc, 91%; nickel, 87%; copper, 79%; lead, 52%; and chromium, 42%. As a result of sludge acidification, the viable counts of selected indicator bacteria were decreased to below the detection limit (4 × 103 cfu 100 ml-1), followed by an increase in the mineral fraction of nitrogen (from 6 to 10%) and in the soluble fraction of phosphorous (from 15 to 30%). Although some loss of sludge nutrients can occur during solid-liquid separation following bioleaching, its beneficial effects as metal removal and reduction of pathogenic bacteria are sufficient to consider the potential of this treatment before sludge disposal onto agricultural fields.

Evaluation of the mixtures ammonium phosphate/magnesium nitrate and palladium nitrate/magnesium nitrate as modifiers for simultaneous determination of Cd, Cr, Ni and Pb in mineral water by GFAAS

A method is described for the simultaneous determination of Cd, Cr, Ni and Pb in mineral water samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman-effect background correction system. The electrothermal behavior of analytes during pyrolysis and atomization steps was studied without modifier, in presence of 5 μg Pd and 3 μg Mg(NO3)2 and in presence of 50 μg NH4H2PO4 and 3 μg Mg(NO3)2. A volume of 20 μL of a 0.028 mol L -1 HNO3 solution containing 50 μg L-1 Ni and Pb, 10 μg L-1 Cr and 5 μg L-1 Cd was dispensed into the graphite tube at 20°C. The mixture palladium/magnesium was selected as the optimum modifier. The pyrolysis and atomization temperatures were fixed at 1000°C and 2300°C, respectively. The characteristic masses were calculated as 2.2 pg Cd, 10 pg Cr, 42 pg Ni and 66 pg Pb and the lifetime of the graphite tube was around 600 firings. Limits of detection based on integrated absorbance were 0.02 μg L-1Cd, 0.94 μg L-1 Cr, 0.45 μg L-1 Ni and 0.75 μg L-1 Pb, which exceeded the requirements of Brazilian Food Regulation that establish the maximum permissible level for Cd, Cr, Ni and Pb at 3 μg L-1, 50 μg L-1, 20 μg L-1 and 10 μg L-1, respectively. The recoveries of Cd, Cr, Ni and Pb added to mineral water samples varied within the 93-108%, 96-104%, 87-101% and 98-108% ranges, respectively. Results of analysis of standard reference materials (National Institute of Standards and Technology: 1640-Trace Elements in Natural Water; 1643d-Trace Elements in Water) were in agreement with certified values at the 95% confidence level.

Improved activity and stability of Ce-promoted Ni/γ-A1 2O3 catalysts for carbon dioxide reforming of methane

The CO2 reforming of CH4 was carried out over Ni catalysts supported on γ-Al2O3 and CeO 2-promoted γ-Al2O3. The catalysts were characterized by means of surface area measurements, TPR, CO2 and H2 chemisorption, XRD, SEM, and TEM. The CeO2 addition promoted an increase of catalytic activity and stability. The improvement in the resistance to carbon deposition is attributed to the highest CO2 adsorption presented by the CeO2 addition. The catalytic behavior presented by the samples, with a different CH4/CO2 ratio used, points to the CH4 decomposition reaction as the main source of carbon deposition.

Determination of Cu, Ni and Pb in Aqueous Medium by FAAS after Pre-Concentration on 2-Aminothiazole Modified Silica Gel

This work describes the synthesis and characterization of 2-aminothiazole modified silica gel (SiAT), and the results of a study of the adsorption and pre-concentration (in batch and using a flow-injection system coupled to an absorption atomic spectrometer) of Cu(II), Ni(II) and Pb(II) in aqueous medium. The adsorption capacities for each metal ions in mmol g -1 were: Cu(II)= 1.18, Ni(II)= 1.15 and Pb(II)= 1.10. The results obtained in the flow experiments showed a recovery of practically 100% of the metal ions adsorbed in a mini-column packed with 100 mg of SiAT, using 100 μL of 2.0 mol L -1 HCl solution as eluent. The sorption-desorption of the metal ions made possible the application of a flow-injection system for the pre-concentration and quantification by FAAS of metal ions at trace level in natural water samples digested and not digest by an oxidizing UV photolysis.

Competition between humic substances and α-amino acids by metal species

The aim of the present work was to carry out experimental comparison between humic substances (HS) and representative α-amino acids (methionine, methionine sulfoxide and cysteine hydrochloride) in relation to the complexation of biologically active trace elements (Al, Cu, Pb, Mn, Zn, Cd and Ni). A mobile time-controlled tangential-flow UF technique was applied to differentiate between HS-metal and α-aminoacids-metal complexes. Metal determinations were conventionally carried out using a ICP-OES. The results showed that HS may be considered as a selective complexing agents with higher metal bonding capability in relation to Al, Cu and Pb, the fact that may be clinically important.

Four new metal complexes with the amino acid deoxyalliin

The solid complexes [Co(C6H10NO2S) 2], [Ni(C6H10NO2S)2], [Cu(C6H10NO2S)2] and [Fe(C 6H10NO2S)2] were obtained from the reaction of cobalt(II), nickel(II), copper(II) and iron(II) salts with the potassium salt of the amino acid deoxyalliin (S-allyl-L-cysteine). Electronic absorption spectra of the complexes are typical of octahedral structures. Infrared spectroscopy confirms the ligand coordination to the metal ions through (COO-) and (NH2) groups. EPR spectrum of the Cu(II) complex indicates a slight distortion of its octahedral symmetry. Mössbauer parameters permitted to identify the presence of iron(II) and iron(III) species in the same sample, both of octahedral geometry. Thermal decomposition of the complexes lead to the formation of CoO, NiO, CuO and Fe2O3 as final products. The compounds show poor solubility in water and in the common organic solvents. ©2005 Sociedade Brasileira de Química.

Transferênce de metais pesados, flúor e radionuclídeos para solos agrícolas na bacia do rio Corumbataí (SP)

The use of phosphate fertilizers and amendments in sugar cane crops may increase the concentration of some elements in soils, from where they would become available for plants (principally in acid soils) and transferred to me human food chain. This paper reports the transference of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn), fluorine and radionuclides ( 238U, 234U, 226Ra, 232Th and 40K) from phosphate fertilizers and amendments to agricultural soils at Corumbatal River basin (SP). The products utilized and colleted in sugar cane crops at Corumbatai River basin are: phosphate fertilizers NPK 5:25:25 (two samples), limestones (three samples), phosphogypsum (two samples) and KCl (two samples). The heavy metals were determined by atomic absorption spectrometry (AAS), fluorine by potentiometry and radionuclides by alpha and gamma spectrometry. Heavy metals (17.8, 31.2, 75.2, 69.5, 138.8, 114.9 and 342.9 g/ha of Cd, Cr, Cu, Ni, Pb, Zn and F, respectively) and radionuclides (0.47, 0.16, 0.17 and 6.33 Bq/kg of soil to 238U, 226Ra, 232Th and 40K, respectively) incorporated in phosphate fertilizers and amendments are annually added in the sugar cane crops, but if utilized in accordance with the recommended rates, they do not raise the concentration levels in soils up to hazards values.

Microstructural and electrical properties of the sofc anode precursor YSZ/NiO composite prepared by A liquid mixture technique

A detailed study of the microstructural and electrical properties of the yttria-stabilized zirconia/nickel oxide (YSZ/NiO) composite was performed. This material is the precursor to the solid oxide fuel cell anode cermet YSZ/Ni. A liquid mixture technique was developed to produce the YSZ/NiO composite to fabricate high-performance SOFC anodes. This technique resulted in fine and homogeneous powders and specimens with high electrical conductivity. The combined results showed that this technique is suitable for the production of the anode cermet.

Processamento de nanomateriais em hidrotermal convencional e hidrotermal de microondas

Copper, zinc and nickel oxides present different properties in nanostructured form. These nanomaterials present very interesting morphologies such as urchin and flowers. This differents arquitechures can be employed in near future in several areas of applications as: nanocatalysis, nanooptoeletronic and nanomedicine.

Evaluation of the performance of α-SiAlON tool when turning Ti-6Al-4V alloy without coolant

Due to their high hardness and wear resistance, Si3N4 based ceramics are one of the most suitable cutting tool materials for machining cast iron, nickel alloys and hardened steels. However, their high degree of brittleness usually leads to inconsistent results and sudden catastrophic failures. This necessitates a process optimization when machining superalloys with Si3N4 based ceramic cutting tools. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. This paper evaluates the performance of α-SiAlON tool in turning Ti-6Al-4V alloy at high cutting conditions, up to 250 m min-1, without coolant. Tool wear, failure modes and temperature were monitored to access the performance of the cutting tool. Test results showed that the performance of α-SiAl0N tool, in terms of tool life, at the cutting conditions investigated is relatively poor due probably to rapid notching and excessive chipping of the cutting edge. These facts are associated with adhesion and diffusion wear rate that tends to weaken the bond strength of the cutting tool.

Investigation of the metal/porcelain interface in LASER-welded Ni-Cr-Mo alloy

The interface formed between the metal and the porcelain of laser-welded Ni-Cr-Mo alloy was studied on a metallurgical basis. The characterization was carried out by using optical microscope, electron scan microscopy and X-ray dispersive spectroscopy techniques and mechanical three-point flexion tests, in the laser-welded region, with and without porcelain. The union of the porcelain with the alloy is possible only after the oxidation of the metallic surface and the subsequent application of a bonding agent known as opaque. The porcelain applied to the base metal and weld bead showed different behaviours - after the flexion test, the base metal showed cracks, while that in the weld bead broke away completely. It was noted that the region subjected to laser welding had lower adherence to the porcelain than the base metal region, due to microstructural refinement of the weld bead. These results can be shown by the X-ray dispersive spectroscopy carried out on the regions studied. The flexion tests demonstrated that the Ni-Cr-Mo alloy subject to laser welding had significant alterations in its mechanical properties after application of the porcelain.

Leaching of Ni and Cu from mine wastes (tailings and slags) using acid solutions and A. ferrooxidans

The objective of this work is to evaluate the acidic and biological leaching of tailings containing Ni/Cu from a flotation and smelting plant. Acidithiobacillus ferrooxidans, strain LR, was used for bioleaching at pH 1.8 and chemical controls were run parallel to that. The acidic leaching was done within 48 hours at pH 0.5 and 1.0. In the slag inoculated flasks the redox potential was high (600 mV), thus indicating oxidative bacterial activity, however, the obtained results after 15 days showed only around 13% Ni and 8% Cu extractions, which were not different to those of the controls. For the flotation tailings bioleaching extractions were approximately 45% for Ni and 16% for Cu while differing figures were obtained for the chemical controls. These were 30% and 12% respectively. Here we could observe that the presence of bacterial activity led to a higher solubility of Ni. Acid leaching of slag showed higher nickel and copper extractions: 56% and 24% respectively at pH 0.5 and 21% and 11% at pH 1.0. However, the acid consumption was 320 and 150 Kg/ton of slag, respectively, both much higher than in bacterial assays. These results indicated that Ni and Cu solubilization from the slag is acid dependent no matter the redox potential or ferric iron concentration of the leaching solution. For flotation tailings, acid treatment showed extractions of 23% for Ni and 16% for copper at pH 0.5 and 22% and 28%, respectively at pH 1.0. The acid consumption was also higher: 220 and 120 Kg/ton, at pH 0.5 and 1.0, respectively. Based on own findings we could observe that acid leaching is found to be more effective for slag, though the acid consumption is much higher, while for the flotation tailings, bacterial leaching seems to be the best alternative. © (2009) Trans Tech Publications.

Exploratory study on sequestration of some essential metals by indigo carmine food dye

Indigo carmine forms a stable complex with different ions, and the stability constant of the complexes were evaluated as log K equal to 5.75; 5.00; 4.89 and 3.89 for complexes with Cu(II), Ni(II), Co(II) and Zn(II) ions, respectively, in 0.1 mol L -1 carbonate buffer solution at pH 10. The interaction between Cu(II) ions and indigo carmine (IC) in alkaline medium resulted in the formation of the Cu 2(IC) complex, measured by the spectrophotometric method, with a stoichiometric ratio between indigo carmine and metal ions of 2:1 (metal-ligand). The reported method has also been successfully tested for determination of copper in pharmaceutical compounds based on copper-gluconate without pre-treatment.