The optimum AI(III) activation conditions for white bentonite (Ordu, Turkey), used as a bleaching agent for cottonseed oil, were investigated. AICl(3) -clay suspension was hydrolyzed in situ using NaOH to investigate possible pillars. Five controllable factors that mainly affect the activation process were specified as initial AlCl3 concentration (F1), OH-/Al3+ molar ratio (F2), NaOH volumetric flow-rate (F3), cation-exchange temperature (F4) and thermal treatment temperature (F5). Each factor was examined at four levels by using a robust (Taguchi) design to determine optimum activation conditions. The response variable of each experimental run was taken as bleaching efficiency, which is defined in terms of absorbance at 420 nm. The effect of desired levels of factors to the system response was compared using the signal-to-noise (S/N) ratio. An importance factor (IF) was suggested in order to compare the affectability of each factor to the response variable by using the integrated area under the S/N ratio curves. The most important factor affecting bleaching efficiency was F5, followed in sequence by F2 > F1 > F4 > F3. The availability of Al-O species after activation in the clay crystal structure was determined by FTIR analysis. The optimum levels of each factor for Al3+ activation of clay were F1 5 meq g(-1) clay, F2 2.0, F3 1200 m Lh(-1), F4 25 degrees C and F5 700 degrees C. (c) 2005 Society of Chemical Industry.