Kinetics studies of groundnut oil bleaching using activated clay as adsorbent

Abstract

Kinetic study of the bleaching of crude groundnut oil was carried out using activated clay as the adsorbent to determine its suitability as an adsorbent for the bleaching process. It involved the study of the bleaching process as a refining process to eliminate and reduce unwanted minor components present in crude groundnut oil extracted from seeds through extraction process. The study estimated the effect of time, adsorbent concentration and temperature on the efficiency of the bleaching process. The bleaching efficiency improved with adsorbent concentration and temperature, with time not affecting the process like other parameters. Efficiency of bleaching was estimated by measuring the absorbance using a double-beam spectrophotometer at a wavelength of 450 nm. Using the Association of Analytical Chemists 1990 the physiochemical properties of crude and bleached oil was determined. At optimum conditions of 100^oC temperature, reaction time of 30 mins and 6 % adsorbent dosage concentration. The acid value, free fatty acid content, saponification value and specific gravity all reduced from, 5.61 mgKOH/g to 3.93 mgKOH/g, 2.81% to 1.97%, 216.5 mgKOH/g to 190.2 mgKOH/g and 0.916 to 0.914 respectively whereas pH remained the same. The kinetics of the bleaching process was best described with the pseudo first order isotherm. Freundlich isotherms was more suitable in the description of the bleaching process due to its relatively high linearity and efficiency of adsorption in the liquid phase. With a rate constant of 0.82, it can be concluded that activated clay is a suitable adsorbent for rapid adsorption of materials from crude groundnut oil. From the result, it can be concluded that activated clay is a suitable adsorbent for the bleaching process and bleaching as a refining process is essential to improve oil quality and shelf life of edible oil.