Vermiculite was treated with 0.8 M solutions of hydrochloric and sulphuric acids for 2, 8, and 24 h. The obtained materials were characterized with respect to their composition (XRF), structure (XRD, FTIR, UV-vis-DRS), texture (BET), surface acidity (NH3-TPD) and catalytic properties. Modification of vermiculite with acids significantly increased its surface area and pore volume and led to partial leaching of iron, aluminium and magnesium ions from its octahedral sheets. Efficiency of the leaching process depended on its duration and the nature of acid used. Acid treatment strongly modified the vermiculite structure leading to a distinct increase of its catalytic activity in the selective catalytic reduction of nitric oxide (SCR NO) process. In a series of the studied samples the best catalytic performance was found for vermiculite treated with sulphuric acid for 8 h. (c) 2012 Elsevier B.V. All rights reserved.