الفهرس 
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Abstract
Bleaching is one of the most cost-intensive processes for refining vegetable oils caused
mainly by the consumption of bleaching agents and oil losses in the spent bleaching.
Therefore, all refineries trying to reduce the cost of bleaching earth (nearly 20% of the total
operating cost). In Egypt, The bleaching earth used is imported from a range of countries like
China, India, Italy, and Germany. To reduce the cost of bleaching earth in Egypt, low-cost yet
efficient adsorbents for vegetable oil bleaching are urgently needed. Therefore, this study
mainly focused on the use of Egyptian bentonite and testing its bleaching capacity for
vegetable oil and determined the optimal conditions for a successful bleaching process.
The experimental investigation of this research includes the preparation and extensive
characterization of Egyptian raw bentonite, activation of bentonite clay with different acids at
different acid concentrations, activation times and different dry clay/acid ratios. The acid
activated bentonite samples were tested for the assessment of their bleaching efficiency for
vegetable oil in the laboratory. The optimum conditions for a successful bleaching process
were also determined.
The obtained results revealed the following:
1) Raw bentonite samples were characterized using the XRD, SEM, and EDX analyses. The
XRD and EDX analysis indicated that bentonite sample contained quantities of
montmorillonite, silicon oxide, quartz, and iron oxides (sodium and calcium). The major
elements in the studied bentonite are silicon which represents 52.6% of the total elements
and 16.8% aluminum and14.6%. iron and a small percentages of Na, Ti, Zn, Cl, Ca, Mn,
and Mg elements. The CEC of the used bentonite clay was75 meq/100g and the swelling
index value was 18cm.
2) The raw bentonite samples were activated using different concentrations of H2SO4, HCl,
and H3PO4. XRD results proved that activation with H2SO4 caused structural changes in
the treated bentonite clay. Silicon content increased to 62.1 % whereas AL and Fe
contents decreased by 13.7% and 10.2% respectively, followed by dissolution and
leaching of exchangeable cations Al +
, K+
, Na+
, and Ca2
. The SEM of activated Bentonite
show more porous and fine grains particles, on the surface of activated bentonite which
causes density decrease to about 750 g/l.
3) The FTIR spectra of Bentonite before and after acid activation indicate the active rules of
Al-O-Si, Al-OH-Al, and Si-O stretching groups, after acid activation the band at 913.04
cm−1 associated with Si-Al-OH vibration disappeared, and there was a transformation of
bentonite structure noticed at 794.97, 696.31 and 534.01 cm-1
, which increased after the
acid treatment.
4) Optimum bleaching performance for activated bentonite types: the results showed that
the bleaching performance of acid activated bentonite was 75.7 % for 4N sulfuric acid
followed by hydrochloric acid (70.5%) and phosphoric acid (40.7 %) at 110 °C. The
optimal time for colour removal was found to be 30 minutes.
5) Optimization of parameters affecting carotene adsorption performance by sulfuric acid
activated bentonite: Carotene removal by 4N sulfuric acid activated bentonite best
achieved at 1 % dosage, 110 C° and 40 min. contact time.
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6) Reliable prediction of carotene adsorption parameters including maximum sorption
capacity was further analyzed using Langmuir, Freundlich, Elovich, Temkin, Fowler–
Guggenheim (FG), Kiselev, and Hill-de Boer isotherm models. Langmuir was quite
successful in precisely describing carotene sorption data, the maximum carotene
adsorption capacity (𝑞max) in activated bentonite was 10000 (mg/kg) at 110 C°.
Meanwhile, second-order kinetics model was very successful in describing the kinetics of
the carotene adsorption. It is therefore suggested that the dominant sorption mechanism
could be chemisorption.
7) Thermodynamics study for carotenes adsorption showed that temperature increased the
carotene adsorption on the activated bentonite and suggests the endothermic character of
carotene sorption. Gibbs free energy (ΔG°) values were all negative which indicate the
spontaneous nature of carotene sorption on bentonite and the removal process is favored
at higher temperatures. Enthalpy (ΔH°) values were positive which indicated the
endothermic reactions for β carotene adsorption which absorb heat from the surroundings
to complete the adsorption process. Positive Entropy (ΔS°) values increased with
increasing concentration values (0.25, 0.5, 0.75, 1, and 1.25%), which indicated
randomness increase at the solid solution interface suggesting the dissociative
mechanism between β carotene and activated bentonite, and significant changes occurred
in the internal structures of the adsorbent during the process.