Adsorption of gossypol from cottonseed oil on oxides

The adsorption of gossypol, a toxic pigment and the major colorant in cottonseed oil, has been studied, using silicas and aluminas of different surface areas and pore size distributions. Gossypol has a high affinity for alumina surface, the adsorption isotherm follows the Langmuir equation, and the maximum amount adsorbed is compatible with a monolayer of molecules on the surface; this is indicative of chemisorption. The affinity for a silica surface is much lower and the adsorption isotherm follows the Freundlich equation. The amount adsorbed is also influenced by the pore size distribution, the useful surface area being that developed by pores larger than 3 nm, i.e., 2 to 3 times the size of the adsorbate. (C) 2000 Academic Press.