The use of different adsorbents for selective removal of compounds from olive residue oil miscella

Abstract.

The selective removal of several impurities from a solution of crude olive residue oil in n-hexane (miscella) using batch adsorption by different materials, used separately or in sequence, was investigated. The following adsorbents were tested: activated diatomaceous earths, powdered activated carbon and synthetic neutral resins ("Amberlite XAD-4, XAD-7, XAD-16). The adsorption efficiency of every group of compounds depended on the adsorbent and the ratio (amount of adsorbent/amount of oil) used. The activated earths and carbon were very much more effective in the adsorption of the compounds from the miscella than the resins. Results were similar for every resin tested. An effective removal of green pigments (chlorophylls and pheophytins) and carotenoids was achieved with every adsorbent tested. With respect to the adsorption of conjugated hydroperoxides (HP), a removal of 50–60% was attained with activated carbon and earths, in contrast to a 20% removal by the resins.

For the final oxidation products (FOP), a 60% removal was observed with powdered carbon, 20–30% with earths and 20% with resins. A removal of 20% of free fatty acids (FFA) by activated earths or powdered carbon and 40% by the resins was observed.

When the adsorbents were used in sequence (carbon or earths followed by XAD-7 resin), the resin was able to adsorb the remaining FFA, HP and FOP.