Commercial activated earths and activated clays based on aluminosilicate minerals, from different
manufacturers, as well as activated carbon, are used for bleaching vegetable oils. Their structural and
chemical composition, specific surface area and porosity are a good basis for application in the
bleaching process of vegetable oils, which improves the color, reduces the peroxide number and soap
content, and reduces and/or completely removes undesirable compounds.
In this paper, bentonite powder (“Bentoprodukt” a.d. Šipovo, Republic of Srpska) was activated with
8 wt% H2SO4 at the following parameters: mass of calcined bentonite powder 160 g, mass of 8 wt%
H2SO4 solution 800 g, activation temperature 95 °C and contact time 30 minutes. The characterization
of bentonite powder before and after activation, and commercial bleaching earth was performed using
several test methods (XRPD, FTIR, BET, SEM/EDS).
Bleaching of raw sunflower oil (“Bimal” a.d. Brčko) with activated bentonite powder and commercial
bleaching earth was carried out in laboratory conditions at the following parameters: temperature 95
°C, time 30 minutes and proportions of bleaching agents 0.2 wt%; 1.0 wt%; 2.0 wt% and 3.0 wt%. In
sunflower oil samples before and after bleaching, soap content, peroxide number, color, then fatty
acid composition by gas chromatography (GC-FID) and oil loss in the bleaching process were
determined.
The test results showed that the activation of bentonite powder leads to an increase in its BET specific
surface area, micropore surface area and volume, higher adsorption capacity, but also a decrease in
particle size. The effects of bleaching of sunflower oil are: no residual soaps, reduction of peroxide
value and small changes in the composition of fatty acids. The obtained values are in accordance with
the Rulebook on the quality of sunflower edible oil, and the effects of bleaching with activated
bentonite powder are similar to the effects of bleaching with commercial bleaching earth.
