Bleaching of crude palm oil using clays in Namayingo district, Eastern Uganda.

Abstract

The bleaching earth used for color improvements of vegetative oils is processed from natural clays worldwide. Uganda’s rich volcanic clays from most regions remains unutilized. The aim of the study was to evaluate the use and efficiency of clay mined locally at Namayingo to bleach vegetable oils when activated by leaching in hydrochloric acid of varying concentrations. The effectiveness of raw and acid activated clays developed from local Ugandan clay from Mutumba, Namayingo District of south Eastern Uganda for bleaching crude palm oil was studied. Hydrochloric acid of varying strengths 0, 10, 20 and 30% was used for the activation. Mixture of the degummed oil and clay powder dosage of 4% placed in Pyrex glass flasks, fitted with a magnetic stirrer was placed in an iso-electric mantle thermostat at 110°C for a duration ranging from 15 to 60 minutes before being cooled and filtered to record absorbance. Samples were subjected to hydrochloric acid activation with 10, 20 and 30% acid at 110°C. Bleaching efficiency for Crude palm oil was studied. The 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 45 minutes at 110°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 the crude palm oil of 62.2% was achieved with clay leached in 30% hydrochloric acid. This study revealed for the first time the use of Namayingo clay in bleaching oils when compared to the purchased bentonite type in the analysis which gave 75% absorbance and that of Namayingo clay 62.24% in contact time of 30minutes and activation with acid concentration of 3.0M and dosage of 4% as optimum conditions used in the research.