Прегледај по Аутор "Ostojić, Gordana"

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    Determination of Titanium Dioxide Content in Bauxites Using X-ray Fluorescence Spectrometry by Fusion and by Pressing
    (Slovenian Chemical Society, 2018) Blagojević, Dragana; Lazić, Dragica; Kešelj, Dragana; Ostojić, Gordana; Imamović, Mugdin
    Bauxites of different deposits were analysed for their content of TiO2 (mass %), using X-ray fluorescence spectrometry and the reference spectrophotometric method JUS B.G8.514. The samples were prepared in two ways: fusion with a borax technique and pressing, after which beads were formed for the purpose of analysis. Certified reference samples of bauxite were used for producing a calibration curve. The equation for calculating the content of TiO2 (mass %) in the samples of bauxite was derived from the calibration curve. Results of the XRF method were tested statistically by means of the F-test and the t-test (the standard sample of the bauxite and the reference method). The values obtained from the afore mentioned tests for the fusion beads showed that the XRF method was precise and correct and that there were no systematic errors, whereas for the pressed beads this method showed significant systematic errors.
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    Determining the Content of Silicon Dioxide in Bauxites Using X-Ray Fluorescence Spectrometry
    (Iranian Institute of Research and Development in Chemical Industries (IRDCI)-ACECR, 2019) Blagojević, Dragana; Lazić, Dragica; Kešelj, Dragana; Škundrić, Branko; Dugić, Pero; Ostojić, Gordana
    The X-ray fluorescence spectrometry and the MA.BM.006 reference spectrophotometric methods were used to determine the content of SiO2 (%) in bauxites from different deposits. The treatment of samples prior to the analysis involved the following steps: annealing, melting using the borax method, and the formation of beads. Certified reference bauxite samples were used for the calibration curve. The calibration curve was produced with the correlation coefficient of r =0.9999 and the standard error of S = 0.0246. The average residual value between the content of SiO2 determined using the XRF method, and the reference method was 0.045, with a standard deviation of 0.068. The XRF method was statistically verified by the F- and t-tests (using the standard sample and the reference method). The values obtained in the tests show that the XRF method yields accurate results and that there are no standard errors.