The changes of adsorption properties of uncalcined Al-pillared montmorillonite were studied. A soda-activated bentonite from Slovakia was reacted with polymeric hydroxoaluminium salt solutions. During storage in air at room temperature for three years, the basal spacing decreased by 0.15–0.2 nm; the specific surface area was reduced by 80% and the total pore volume by 40–60%. Adsorption experiments from ethanol-cyclohexane mixtures revealed the decreasing adsorption capacity and the increasing hydrophobicity. The changing surface character was also evident in the decrease in enthalpy of immersion in ethanol from 65.3 J/g to 8.3 J/g (sample B) and from 37.8 J/g to 5.2 J/g (sample C). The alteration probably arises from gradual formation of gibbsite-like interlayers and the redistribution of charges.