Papers by Keyword: Nepheline

Abstract: There is presented the method of silicon dioxide obtaining by its extraction from silica-containing solution from nepheline decomposition with the acetone and ethanol help with organic phase subsequent gelatinisation. Structural and surface properties of the obtained SiO₂ samples were investigated. The specific surface area of the obtained samples depends on the preparation method and varies in the range from 559 to 626 m²/g. The particles average diameter varies in the given series of samples from 2.26 to 6.68 nm. It has been found that the use of extraction has no destructive effect on the SiO₂ specific surface area and maintains its original microporous structure.

Abstract: The article presents a method to obtain silica xerogels with developed specific surface based on nepheline concentrate acid decomposition in C₂H₅OH-H₂SO₄ system. It was found that the use of ethanol instead of water produces stable and steady silica gels. It is proved that the use of ethanol results in almost complete deposition of soda alum and aluminum potassium sulphate out of nepheline decomposition solution without its additional cooling, due to their extremely low solubility in alcohol solution. The morphology, structural and surface properties of synthesized xerogel sample with ~600 m²/g specific surface area (based on the analysis) were investigated; its mixed micro-and mesoporous structure was established. Electron probe microanalysis showed chemical purity of the resulting SiO₂.

Abstract: Crystalline alumina samples with Al₂O₃ content of 95.23 wt.% were prepared directly from the nepheline ore in Nanjiang county, Sichuan province of China. Four steps were involved in the experiment of alumina preparation, including calcination, dissolution, carbonation and re-calcination. Lime was used in the calcination process with the nepheline concentrates powders to generate soluble aluminates and insoluble silicates. NaOH solution was used as the mother solution in the dissolution process. CO₂ was introduced into the solution to precipitate the Al (OH)₃ precursor, which was then fired to obtain crystalline alumina. Among the crystalline alumina obtained three phases of crystals existed which were detected by XRD and SEM, including δ-Al₂O₃ as the major phase, while θ-Al₂O₃ and κ-Al₂O₃ as the minor phases. Various crystal phases of alumina could be ascribed to the purity and crystal structure of precursor, as well as the re-calcination temperature and time.

Abstract: Two different glass powders (a commercially available glass frit and a borosilicate glass) have been used as blending agents for sodalite, an aluminosilicate mineral able to condition chloride salt wastes from pyrometallurgical processes. The synthesis of the mineral phase has been made through a process recently proposed by Idaho National Laboratory in USA, starting from a homogeneous powder of nepheline, chloride salts and glass. The mix, put into an alumina crucible, was introduced in a furnace inside an argon-atmosphere glove-box. The furnace temperature was then raised to 925 C, where it was kept for 7 hours. Leach tests under static conditions, according to ASTM C1285-02, have then been carried out on the final waste forms at room temperature (23 C) and in an oven at 90 C. SEM investigations have also been made before and after leach tests, in order to check the status of the powders. In particular the effect of the leaching process on the surface of the sodalite grains at 90 C from 30 to 150 days has been evidenced. The results obtained in the present study have been usefully compared to those from a similar test on a sodalite added with a glass frit by Idaho National Laboratory. Financial support from the Nuclear Fission Safety Program of the European Union is gratefully acknowledged (project ACSEPT, contract FP7-CP-2007-211 267).

Abstract: Lavrinhas, a city located 234 km northeast of São Paulo, Brazil, presents syenitic rocks with high content of nepheline, whose preliminary field assessment indicated its potential to be used in the production of ceramic products. The paper aimed to study this raw material with fluxing properties and to determine the best processing methods based on mineralogy and texture, in order to achieve better removal efficiency of the nepheline. Petrographic characterization was carried out in two rock samples, as well as the particle size characterization of the untreated material, the split into fractions for magnetic separation tests and optical microscope observation of the products. In addition, chemical and particle size analysis and melting tests were performed. The latter concerned the material melting color evaluation before and after the magnetic separation, as well as its potential use in glazes and engobes, compared to a standard sample of Nepheline, and inferences for the use in porcelain masses. Preliminary tests showed that after the removal of residual iron oxide, the nepheline raw material bearer has potential to be used in the formulation of porcelain masses, replacing other fluxing materials with higher benefit.

Abstract: Carbon decomposition of liquor afger desilication from nephine was investigated, aluminium oxide was prepard by anneal of Al (OH)₃ separated out from carbon decompositon, and analysis of radionuclide of both above process was performed. The results show decomposition rate of sodium aluminate can be obtained when experiments of carbon decomposition of liquor after desilication using CO₂ of hight concentration, and it is beneifit for the crystal growth of Al (OH)₃, filtration and separation. Great mass of nuclide exists in the mother solution of carbon decomposition, and few into Al (OH)₃, which could be regarded as wiout radioactive contamination. .