Activation of Raw Bentonite (Afar Region) Using Sulfuric Acid for Rapeseed and Niger Seed Oil Bleaching
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Date
2017-06
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Addis Ababa University
Abstract
In this study, a two-stage process was conducted. The first one was carrying out the activation process of raw bentonite at different conditions and the optimum parameter was chosen. The second process was bleaching of Niger seed oil and rapeseed oil using the chosen activated bentonite. The raw bentonite collected from Gewane in Afar region was activated by sulfuric acid and the design of various experiments in order to assess and simulate the effects of the acid activation of raw bentonite on the bleaching capacity of Niger seed oil is described.
Two key parameters of the acidic activation, namely acid concentration and activation temperature, were considered. The highest bleaching capacity was obtained around 3M acid concentration and at 90oC of activation temperature as optimal activation. The raw and activated bentonite at optimal condition was characterized by XRD, FTIR and SEM with EDS. The results of the XRD showed that the raw bentonite is composed of montmorillonite, quartz, muscovite, hematite, feldspar and cristobalit. X-ray and FTIR data confirmed that acid activation affects both the octahedral and the tetrahedral sheets. The results of the analysis by Energy Dispersive Spectroscopy (EDS), showed that, presence of silica, alumina and iron as major constituents, along with traces of sodium, potassium, magnesium, calcium, and titanium in the form of impurities. These exchangeable cations were removed partially by acid attack.
Full factorial experimental design was employed to correlate the bleaching parameters (temperature, time and dosage of clay) to the percentage color reduction for Niger seed and rapeseed oil bleached. The result showed that the optimum condition for the bleaching process was a temperature of 900C, a period of 30 minutes and 4 % clay dosage which resulted in 94.37% bleaching of the Niger seed oil. For rapeseed oil, the maximum bleaching efficiency, which is 96.01%, was obtained at 110 0C, a time period of 45 minutes and 1% clay dosage. The experimental result was in agreement with the model prediction.
Generally, the study has shown that the clay is a good adsorbent for the bleaching of both oils. This research has further established that acid activated bentonite has the power to remove not only pigments but also reduce the free fatty acid of unbleached oils.
Keywords: Bentonite, Acid activation, Characterization, Bleaching, Niger seed oil, Rapeseed oil
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Bentonite; Acid activation; Characterization; Bleaching; Niger seed oil; Rapeseed oil