Author(s):
1. Zoran Petrović, Faculty of Technology - University of East Sarajevo, Republic of Srpska, Bosnia and Herzegovina
2. Bojana Pečenica, Tehnološki fakultet Univerziteta u Istočnom Sarajevu, Karakaj 34a, 75400 Zvornik, Bosna i Hercegovina, Republic of Srpska, Bosnia and Herzegovina
3. Aleksandra Radulović, University of Belgrade, Institute of General and Physical Chemistry, Studentski trg 12/V, Belgrade, , Serbia
4. Dragana Kešelj, Tehnološki fakultet Zvornik Univerziteta u Istočnom Sarajevu, Republic of Srpska, Bosnia and Herzegovina
5. Pero Dugić, Faculty of Technology Banja Luka, Republic of Srpska, Bosnia and Herzegovina
6. Sabina Begić, Faculty of Technology, University of Tuzla, Federation of Bosnia and Herzegovina , Bosnia and Herzegovina
7. Tatjana Botić, Faculty of Technology Banja Luka, Republic of Srpska, Bosnia and Herzegovina

Abstract:
Due to its porous structure and high specific surface area, silica gel is widely used in various adsorption processes. Crude soybean oil contains various impurities, including phosphatides, tocopherols, sterols, pigments, free fatty acids, and trace metals. The reduction or complete removal of these impurities is achieved through several refining steps, one of which is the bleaching process using commercial bleaching earths and activated clays with high specific surface areas and excellent adsorption capacities. In this study, silica gel (particle size 80–200 μm; Zeochem, Zvornik) and an imported commercial bleaching earth were used for bleaching crude soybean oil supplied by Viktoria Oil (Šid, Serbia). The bleaching process was carried out at 95 °C for 30 min using bleaching agent concentrations of 0.5, 1.0, 1.5, and 2.0% (w/w). The silica gel and commercial bleaching earth were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDS), Brunauer–Emmett–Teller (BET) surface area analysis, and laser particle size analysis. The results showed that the silica gel exhibited a 2.91-fold higher specific surface area and a 2.69-fold greater total micropore volume than the commercial bleaching earth, while its average pore diameter was 2.07-fold smaller. The d10 and d50 particle size values of the silica gel were 3.01- and 1.46-fold higher, respectively, than those of the commercial bleaching earth, whereas the d90 values were comparable. Energy-dispersive X-ray spectroscopy (EDS) analysis at 1000× magnification showed that the silica gel consisted of 62.79% O and 33.13% Si, with minor amounts of Na, Cu, Zn, Hf, and W. The bleaching efficiency was evaluated by physicochemical analyses and gas chromatography with flame ionization detection (GC-FID). The results showed that no soap residues remained in the soybean oil after bleaching. In addition, the peroxide value, chlorophyll content, and free fatty acid content decreased, while only slight changes were observed in the oil color and fatty acid composition. Furthermore, the use of silica gel during the bleaching process resulted in lower soybean oil losses compared with the commercial bleaching earth.

Key words:
80-200 µm silica gel, silica gel characterization (XRD, FTIR, SEM/EDS, BET), crude soybean oil, soybean oil bleaching, bleaching effect, fatty acid composition (GC-FID), oil loss

Date of abstract submission:
31.07.2026.

Conference:
Contemporary Materials 2026 - Savremeni Materijali

Applied paper from author