Removal of phosphorus from vegetable oil by acid-activated sepiolite

The adsorption of phosphorus (P) from rapeseed oil on acid-activated sepiolite (AAS) was investigated for different AAS dosages and bleaching temperatures. The P concentration in the oil was reduced from 29.7 to 1.11 mg/kg at the optimal conditions; bleaching temperature -100 degrees C, AAS dosage -1.5%. The adsorption capacity of AAS in relation to P and mean adsorption energy were calculated according to Lingmuir and Freundlich models and the former was found to be better. The negative values of free energy of adsorption (Delta G(ads)(o)) Show that the adsorption is spontaneous, whereas the positive value of the entropy of adsorption (Delta S-ads(o)) probably results from the reorganisation in the internal structure of the adsorbent appearing during adsorption of P oil AAS. The low value of adsorption enthalpy (Delta H-ads(o)) indicates a relatively-weak adsorbate-adsorbent affinity probably due to hydrogen bond formation. The division of phospholipids and phosphates between external surface and micropores of the sepiolite is suggested. (c) 2008 Elsevier Ltd. All rights reserved.