Abstract: The adsorption behavior and mechanisms of anionic heavy metal Cr(VI) on purified bentonite have been investigated.The results showed that the surface zeta potential of bentonite was negative at pH=2-12.The adsorption efficiency was decreased with the increase of the solution pH value.The adsorption process followed the pseudo-second order kinetic model and Freundlich isotherm very well, and adsorption rate is mainly influenced by the membrane diffusion.The thermodynamic parameters indicated that the adsorption process of Cr(VI) on bentonite was an endothermic and spontaneous process.A small amount of Cr (VI) can be converted to Cr³⁺by reducing the reaction at low pH value range, and then the ion exchange and surface complexation between Cr³⁺and bentonite partly contributed to Cr(VI) adsorption on bentonite.At low initial concentration of Cr(VI), the adsorption of Cr(VI) was mainly dominated by inner-sphere surface complexation, whereas physical adsorption was another adsorption mechanism at high initial concentration of Cr(VI).