Прегледај по Аутор "Lazić, Dragica Z."

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    Determination of silicon dioxide content in bauxite: comparing the ICP-OES method with the UV-VIS method
    (Platform and Workflow by OJS/PKP, 2022) Ostojić, Gordana S.; Lazić, Dragica Z.; Zeljković, Saša M.
    In this paper, the ICP-OES method (induced coupled plasma optical emission spectrometry) was used to determine the content of silicon dioxide in bauxite, as an important impurity that affects the quality and application of bauxite in alumina production by the Bayer process. Twenty bauxite samples from seven different deposits were analysed. The results were compared with the reference spectrophotometric UV-VIS method. The mean relative difference between the silicon dioxide content determined by the ICP-OES method and the reference method is found to be 4.88 %. Statistical tests were used to assess the comparability of the two methods, followed by a scatter plot, the Bland Altman, Passing-Bablok, and the "Mountain" plot. Graphical comparisons generally do not show statistically significant differences between methods. The accuracy and precision of the ICP-OES method were verified by using the standard reference material SRM NIST 697, Dominican Bauxite. Recovery and repeatability values, expressed as relative standard deviation (RSD), are within the acceptance criteria. Based on the t-test, there is a statistically significant difference between the mean value of ICP-OES measurements and the certified value of silicon dioxide, which can be attributed to the effect of systematic error of ICP-OES analysis.
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    Uticaj stepena kristaličnosti, sadržaja aluminijum-oksida i natrijum-oksida na kapacitet sorpcije vode NaY zeolitom
    (Association of the Chemical Engineers of Serbia, 2016) Kešelj, Dragana M.; Lazić, Dragica Z.; Živković, Živan D.; Škundrić, Branko T.; Penavin-Škundrić, Jelena V.; Sladojević, Slavica G.
    U radu su prezentovani matematički modeli koji opisuju zavisnost kapaciteta sorpcije vode od stepena kristalizacije, sadržaja Na2O i Al2O3 u NaY zeolitu. Pri različitim uslovima kristalizacije, sintetisan je NaY zeolit iz natrijum-aluminatnog rastvora, vodenog stakla i sumporne kiseline. Dobijeni zeolitski prahovi okarakterisani su na sledeće parametre: Na2O, Al2O3, kapacitet sorpcije vode (WSC) i stepen kristaličnosti (SK). Regresionom analizom uzoraka zeolitskih prahova, u kojima su se vrednosti kretale za: sadržaj Na2O u intervalu 13,81 do 16,14%, Al2O3 od 21,58 do 27,17%, SK od 58,70 do 114,00% i WSC od 21,32 do 36,59%, došlo se do zaključka da postoji značajna korelacija između kapaciteta sorpcije vode i stepena kristaličnosti, za razliku od sadržaja Na2O i sadržaja Al2O3 u zeolitskom prahu, čija se korelacija sa kapacitetom sorpcije vode, može zanemariti. Matematički model dobijen linearnom regresionom analizom imao je visok R2 = 0,796, dok je bolji matematički model dobijen nelinearnom regresionom analizom R2 = 0,912, kojom je kapacitet sorpcije vode iskazan preko kvadratnog modela.