A Study of the Adsorptive and Oxidative Bleaching of Palm Oil Using Clay and Potassium Tetraoxomanganate V11 Materials

Abstract

Fats and oils undergo hydrolysis reaction. They hydrolyse to yield propane-1,2,3 triol and the corresponding alkanoic acids if it is acid hydrolysis. Alkaline hydrolysis yields sodium or potassium salt of the alkanoic acid and propane-1,2,3-triol. A common approach for bleaching palm oil has been the use of clay materials, particularly the commercially available fuller’s earth. In this study, the suitability of chemical bleaching of palm oil using acidified (0.1M H2SO4) and non-acidified 1.0M KMnO4 was examined. This is compared to the adsorptive procedure using clay materials. Average bleaching absorbance values of 0.017+0.005 and 0.115+0.004 for acidified and non-acidified KMnO4 were respectively obtained from the oxidative bleaching procedure. Those for fuller’s earth and its blend with sodium sesquicarbonate (trona, a locally obtained clay) gave absorbance values of 0.121+0.011 and 0.186+0.006 respectively; while that for trona/activated carbon blend was 0.234+0.007. These are in comparison to 0.881 for the unbleached palm oil. Thus, a relatively better bleaching was achieved with the oxidative process. A first order rate reaction with respect to the bleaching agents was obtained for both procedures. Rate constants of 0.079+014 (acidified) and 0.055+0.020min-1 (non-acidified) at 800C were recorded for the oxidative bleaching. These are compared to 0.034+0.009 obtained for the clay mixture. Half-life values of 10min for acidified oxidative process, and 28min for adsorptive clay mixture method, were obtained. Efficiency of 98% was obtained for the acidified oxidative compared to approximately 70% for the clay blend. A significance, p< 0.05, between the absorbance values for the acidified oxidative and each of the adsorptive clay bleaching procedures was obtained.These observations indicate the potentials of oxidizing agents especially the acidified KMnO4 in the bleaching of palm oil, and therefore, suggest its usage industrially for this purpose.