Modelling adsorption of impurities from a vegetable oil in organic solution: the use of blends of activated carbon and earths

In this study, the use of blends of activated powdered carbon and activated earths for the selective removal of several impurities (pigments, free fat ty acids and oxidation products) directly from the solution of crude olive residue oil in n-hexane (miscella) was investigated. The optimization of batch adsorption process was carried out in a 30% oil m iscella (the usual miscella concentration) via the Response Surface Methodo logy as a function of both the amount of total adsorbent (TA) and the perce ntage of activated earths (E) used in these blends with carbon. Both the ad sorption of pigments (chlorophylls and carotenoids) and hydroperoxides was significantly affect-ed by TA and E (linear and/or quadratic terms). In add ition, an interaction effect (TA x E) was observed on the reduction of the residual content of these compounds. However, for final oxidation products (FOP), no interaction effect (TA x E) was observed and only the linear term s of TA and E showed to be significant on the response. Tridimensional response surfaces, described by second order polynomials, we re fitted to the experimental data points concerning the residual content o f pigments and initial oxidation products in miscella. The adsorption of FO P was fitted to a flat surface. In organic solution, the selective batch adsorption to the blends of activa ted earths and carbon occurs in the following order: chlorophylls > caroten oids > hydroperoxides > final oxidation products. In fact, the minimum valu es observed for residual contents of chlorophylls, carotenoids, hydroperoxi des and final oxidation products, were, respectively, about 5, 11, 25 and 4 1%. The addition of mixtures of carbon with earths directly to the miscella sho wed to be more efficient than carbon or earths alone, similar to the observ ation in a solvent free classical bleaching.