Effect of OH/(Fe + Al) ratio, aging time of Fe,Al-containing pillaring solution on physicochemical properties of Fe,Al-pillared clays (Fe,Al-PILCs) obtained from Mukhortala (Buryatia) montmorillonites and the change of these properties with the calcination temperature were examined. Characterization studies were performed by use of XRD, FTIR, DR-UV-vis, Al-27 NMR and N-2-adsorption/desorption analysis. It was found that the prolonged aging time of the Fe,Al-solution (Al/Fe = 10/1) favours the increase in total surface area, total pore-volume and micropore volume of Fe,Al-PILCs. The relationships between preparation conditions, iron state, catalytic activity and stability to leaching were revealed in hydrogen peroxide oxidation of phenol and monoazo dye acid chrome dark-blue (ACDB), The state of iron atoms can be controlled by Al/Fe and OH/(Fe + Al) ratios, aging period of Fe,Al-pillaring solution and calcination temperature. The increase in Al/Fe ratio and calcination temperature from 400 degrees C to 500 degrees C reduces to the decrease in the formation of oligomeric iron species. The increase in aging time of Fe,Al-pillaring solution reduced to decrease in iron leaching and increase in reaction rate due to the formation of isolated iron species. (C) 2008 Elsevier B.V. All rights reserved.