Cetyltrimethylammonium modified birnessite (CTMA-birnessite) is prepared by a simple hydrothermal method. The synthetic birnessite materials are characterized by a number of characterization techniques, including powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the prepared CTMA-birnessite has a basal spacing up to 3.28 nm and that both the CTMA-birnessite and the birnessite have layer structures and plate-like forms with a thickness of less than 0.1 mu m. The relative contents of Mn2+, Mn3+ and Mn4+ on the sample surfaces are about 22.1%, 56.4% and 21.5% for birnessite, and 9.5%, 62.4% and 28.1% for CTMA-birnessite. The CTMA-birnessites show excellent adsorption/desorption properties for benzoic acid. At least 20% of the benzoic acid is adsorbed to the CTMA-birnessite in the adsorption experiment. (C) 2014 Elsevier B.V. All rights reserved.