Membrane processing of used frying oils

Studies were conducted with used frying oils in a flat membrane batch cell using five different types of polymeric membranes to decrease the soluble d egradation products. During membrane processing, triglycerides permeated pr eferentially compared to the majority of the polar compounds including oxid ation products, polymers, and color compounds. Two of the composite membran es, NTGS-AX and NTGS-2200, selectively rejected polar compounds and oxidati on products to the extent of 25-48% and 24-44%, respectively. The reduction in Lovibond color values (5R+Y) was in the range of 83-93%. The viscosity of the used frying oil was reduced to the extent of 22%. The composite memb ranes were effective in reducing the soluble impurities, as well as insolub le particulates, without causing any undesirable changes to the oil. The me mbrane process appears to improve the life of used frying oils and does not have the disadvantages associated with the active filtration systems, howe ver, for commercial application the permeate flux needs to be improved cons iderably.