1,721,040 research outputs found
THERMOGRAVIMETRY OF A KAOLINITE-ALUNITE ORE
No full textAn ore containing kaolinite (Al2O3 . 2SiO(2) . 2H(2)O), alunite (KAl3(SO4)(2)(OH)(6)), feldspar (KAlSi3O8) and quartz (SiO2) was analysed by TG/DTA to determine the mineralogical composition of samples considered representative of concentrates and tailings likely to be obtained from physical treatments designed to produce a kaolin concentrate as low as possible in alunite. The ore was divided into various particle-size fractions each of which was subjected to TG/DTA analysis. A knowledge of the reactions and the decomposition temperatures of the minerals present permits the application of a system of equations that provides the composition of each size fraction, thus circumventing difficulties due to the overlapping of weight-loss curves during execution of the thermal curve. The alunite results provided by TG are in good agreement with those obtained via standard calculation starting from elemental chemical analysis. The kaolinite results are less accurate but as they follow the same trend as those obtained by chemical analyses, except for the finest fractions, they can be used for relative comparison of samples obtained during a physical treatment testing campaign
Influence of calcium carbonate on the decomposition of asbestos contained in end-of-life products
No full textThree bearing-asbestos wastes, friction material, vinyl-asbestos (linoleum) and cement-asbestos mainly containing chrysotile were characterized. Powder X-ray diffraction (XRDP), scanning electron microscopy (SEM) with microanalysis observations and thermal analysis (TGA/DTA) were carried out on the materials as received and after heating at 1100 C in order to observe their structural changes and thermal behaviours. A quantitative determination of chrysotile in the friction material was also carried out. To study the influence of CaCO 3 on the decomposition of asbestos, the three techniques were also applied on the linoleum and cement-asbestos at room temperature and at 1100 C after leaching of the materials with 1:3 HCl to remove the carbonates present in the wastes. The results show that the presence of CaCO3 prevents the asbestos to decompose according to the known decomposition reactions and leads to the formation of calcium-silicate compounds. When CaCO3 is removed by washing with HCl, decomposition of asbestos proceeds according to the expected reactions. © 2013 Elsevier B.V. All rights reserved
EVALUATION OF THE SELECTIVITY ON THE LA(III)-CE(III) SEPARATION WITH CHELATING EXTRACTANTS
No full textRare earths elements are usually recovered by the processing of ore concentrates (25-30% La2O3; 44-50% CeO2) by acid digestion followed by solvent extraction. The separation of lanthanides by liquid-liquid extraction is widely achieved by TBP and quaternary ammonium compounds (from nitrate solutions); versatic acids and alkylphosphoric acids (mainly D2EHPA) from chloride solutions. Separation factors 1.5-2.5 for neighboring lanthanide, but most stages are required for the separation section. The selective separation of lanthanides Ln could be improved by a proper application of more selective chelating reagents HR. The investigation was concerned with the utilisation of these extractants and in particular nitrogen-bearing reagents. The experimental work was directed towards a quantification of the different extractability of lanthanum(III) and cerium(III) in aqueous chloride solutions as a function of pH, extractant concentration, ligand and metal concentrations. Two commercial reagents have been evaluated: SME529 (an alkyl-hydroxyoxime) and KELEX100 (an alkyl-hydroxy-quinoline). Extraction equilibrium depends mainly on the pH for a particular extractant. The most promising selective reagent has been KELEX100 which has achieved separation factors greater than 200. The behaviour of lanthanides for a particular liquid-liquid system has been explained according to the molecular structure of the metalchelate. The ease of proton release and the donor properties of the nitrogen group of the chelating reagent molecule have been outlined and discussed
Assembly of Mineral Processing Unit Operations for Beneficiation of a Titania-rich Pigment Sludge,
No full textCOMPLETE BENEFICIATION OF LEUCITE BY THERMAL-TREATMENT
No full textHigh-temperature roasting of leucite in the presence of CaCl2 gives rise to a reaction that results in almost complete recovery of its potassium content as KCl. A solid residue consisting mainly of anorthite and silica is also obtained; this could be used as raw material for the production of hydraulic binders. The process is of economic interest because of the relatively low temperatures involved and especially the low cost of the reagents employed, since these find no other valid industrial application at present. Potassium chloride, cordierite and silica are obtained if MgCl2 is used instead of calcium chloride
PRECONCENTRATION OF AN ITALIAN TALC BY MAGNETIC SEPARATION AND ATTRITION
No full textThe work was performed to assess the possibility of preconcentrating a Valmalenco (Italy) talc ore, containing chlorite, carbonates and iron as the main impurities, and adopting magnetic separation and selective attrition grinding. This provides a flotation feed enriched in talc and chlorite
Application of mineralurgical and thermal treatment for the removal of mercury from contaminated material
No full textBeneficiation of alunite ore by pyro- and hydrometallurgycal treatment of alunite-K2CO3 mixtures,
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Rimozione del mercurio da campioni contaminati del Monte Amiata mediante trattamento termico,
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