Bleaching Edible Oils Using Clay from Kangole, Moroto District, North Eastern Uganda

Abstract

The search for natural clays that can be used to provide industrial bleaching earths is worldwide; Uganda’s rich volcanic clays from North Eastern region remain unutilized. The aim of the study was to evaluate the use and efficiency of clay mined locally at Kangole to bleach vegetable oils when activated by leaching in hydrochloric and sulfuric acids of varying concentrations. The effectiveness of raw and acid activated clays developed from local Ugandan clay from Kangole, Moroto District of North Eastern Uganda for bleaching cotton and sunflower seed oil was studied. Hydrochloric and sulfuric acid of varying strengths 0, 10, 20 and 30% was used for the activation. Mixture of the degummed, neutralized oil and appropriate clay powders placed in Pyrex glass flasks, fitted with a magnetic stirrer was placed in an iso-electric mantle thermostated at 90°C in a nitrogen atmosphere for a duration ranging from 10 to 60 minutes before being cooled and filtered to record absorbance. Minerals were identified using IR, XRD, and elemental chemical composition of fusion mixture following Hutchinson’s method. The clay was montmorillonite in character with subordinate Kaolinite and Illite and unaltered tuff in form plagioclase and feldspars. Samples were subjected to hydrochloric and sulfuric acid activation with 10, 20 and 30% acid at 105°C. Bleaching efficiency for cotton and sunflower oils were. Study revealed that maximum decrease in absorbance of bleached oil was attained with clay leached in 30% sulfuric acid when the oil was in contact with clay for 30 to 40 minute at 90°C. Results obtained in which the performance of locally prepared clays was expressed in terms of percentage decrease in absorbance of oil showed that, the acid-activated samples were more effective in the bleaching of oils than raw clay. The percentage decrease in absorbance of sunflower oil of 80% was achieved with clay leached in 20% hydrochloric acid. Yet cotton oil attained highest percentage absorbance of 55% during the bleaching step. This study revealed for the first time the use Kangole clay in bleaching oils. It’s the first time the clay minerals in admixture mined at Kangole has been shown to contain montmorillonite, illite, kaolinite, feldspars and plagioclase which contribute to its bleaching activity.