In this paper, nanostructured MnO2 materials were successfully prepared through a simple and template-free hydrothermal method. X-ray diffraction pattern indicates that the as-prepared nanomaterials are alpha-MnO2. Transmission Electron Microscopy and Scanning Electron Microscopy images demonstrate that nanostructured rod-clusters alpha-MnO2 could be evolved from the nanorods. Brunauer-Emmett-Teller (BET) surface area measurement was employed to characterize the surface property. Moreover, the as-obtained (alpha-MnO2) nanomaterials could act as an efficient adsorbent to remove Congo Red and Methlylene Blue. More significantly, the nanomaterials are nontoxic and environmentally friendly via biological methylthiazolyldiphenyltetrazoliumbromide assay experiments. Its nontoxic and enhanced adsorbability properties guarantee their safe applications in environmental protection and industrial aspects. (C) 2011 Elsevier Ltd. All rights reserved.