Adsorption of gossypol from cottonseed oil on oxides

The adsorption of gossypol, a toxic pigment and the major colorant in cotto nseed oil, has been studied, using silicas and aluminas of different surfac e areas and pore size distributions. Gossypol has a high affinity for alumi na 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 sur face is much lower and the adsorption isotherm follows the Freundlich equat ion. 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.