Environmentally green carbon aerogels have been prepared as adsorbents for dye-containing waste-water. The aerogels were prepared by carbonization of starch aerogels synthesized from soluble starch through a sol gel process followed by drying at ambient pressure. The Brunauer-Emmett-Teller (BET) surface areas and pore size distribution were measured by N-2 adsorption/desorption, and the surface zeta-potential and microstructure of carbon aerogels were characterized using a scanning electron microscope (SEM) and zeta-potential analyzer. SEM images indicate that the carbon aerogels consist of flakes with side length of 60-120 mu m and thickness of 3-4 mu m. The flakes are irregular in shape and composed of spherical carbon nanoparticles of 10-30 nm. The carbon aerogels have both microporous and mesoporous structures and exhibit high specific surface areas, the highest value is 1571 m(2)/g. The mean diameter of the micropores is 0.89 nm and that of the mesopores is 2-10 nm. At pH = 10, the carbon aerogels have a zeta-potential of -40 mV and exhibit high adsorption capacities for cationic dyes, such as crystal violet (CV), methyl violet (MV) and methylene blue (MB), from aqueous solution. The largest adsorption capacities for CV, MV and MB are 1515, 1423 and 1181 mg/g, respectively. (C) 2010 Elsevier Ltd. All rights reserved.