Прегледај по Аутор "Došić, Aleksandar"

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    Ion exchange of sodium with hydrochloric acid in ZSM-5 zeolite
    (Centre for Evaluation in Education and Science (CEON/CEES), 2021) Škrba, Milomirka; Obrenović, Zoran; Došić, Aleksandar; Gligorić, Miladin; Đurić, Biljana; Savić, Ivan
    ZSM-5 zeolites are highly silicate materials that have significant application in catalytic processes in petrochemistry, especially due to their high selectivity. Most reactions in the petrochemical industry are acid-catalyzed. The acidic properties of zeolite depend on the number of acid centers, i.e. the presence of hydrogen ions, and therefore, in this paper the possibility of reducing the sodium content in the pores of high silicate zeolite ZSM-5 with the modulus (SiO2 / Al2O3 = 1000) will be investigated, by applying ion exchange with hydrochloric acid. Chemical analysis of samples before and after ion exchange, and application of instrumental methods of X-Ray diffraction, FT-IR spectroscopy, and SEM analysis monitored the influence of the quantity of hydrogen ions on the chemical composition and the structure of ZSM-5 zeolite at different acid concentrations and at different exchange times. It has been shown that the application of ion exchange with hydrochloric acid can reduce the sodium content in zeolite. Even with the application of 5% HCl for 6 hours, the content of sodium in the zeolite is reduced by over 98%. A similar effect is achieved by applying more concentrated hydrochloric acid solutions for a shorter ion exchange time. By prolonging the ion exchange time, there are no significant changes in terms of the final ion exchange. On the other hand, the application of HCl solutions of higher concentrations leads to a slight decrease in the aluminum content in the zeolite, which may partially affect the structural stability of the zeolite. The results obtained by FT-IR and SEM analysis and X-Ray diffraction confirm the possibility of ion exchange with hydrochloric acid, without significant changes in the crystal structure of the zeolite.
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    Potential Application of Nano Zero Valent Iron in Environmental Protection
    (Springer, 2017) Tomašević Pilipović, Dragana; Kerkez, Đurđa; Dalmacija, Božo; Bečelić-Tomin, Milena; Došić, Aleksandar
    Nanoscale zero-valent iron particles (nZVI) have been studied intensively in recent years as a new and promising technology for environmental remediation. nZVI is a readily available and low-cost reducing agent, which also has high reactivity towards a broad range of contaminants. Nonetheless, pivotal points to be addressed are its stability against aggregation, its mobility in subsurface environments, and its longevity. This chapter gives an extensive review of the progressive research and development activities in regard to environmental protection through iron-based nanoparticles. Methods for synthesis of different types of supported iron-based nanomaterial, as well as their characterization, are discussed. The lack of knowledge is evident regarding use of the same nanomaterials for treating different environmental mediums and various chemical species. Thus, the chapter includes two case studies, covering the usage of several supported nZVI for remediating solid porous media polluted with metals, as well as for treating wastewaters containing dye molecules. Case studies also indicate a broader applicability of these processed materials, emphasizing the possibility for further commercialization of supported nZVI.